Systems Neuro Exam 1

Light response is terminated by 3 mechnisms: explain them

1 G protein transducin self inactives (GTPase activity --> braeks down the boudn GTP of the active form into GDP) 2. Activated rhodopsin (metarhodopsin II) becomes target for phosphorylation by "opsin kinase". Phosphorylated rhodopsin binds to a regulatroy protein (arrestin) which leads to its inactivation, thus blocking its interaction with transducin 3. A FEEDBACK mechanism ensures that large light responses are terminated more quickly (light adaptation)

What are the 4 implications of phototransduction being the way that it is

1 Signals are graded (analog, not digital) signal: NO action potential; short photoreceptors; local processing in retina 2 SLOW: 55 Hz = cone flicker fusion frequency -12 HZ for rods Dark current is metabolically demanding 3 High gain: extremely sensitive (1 photon). Amplification via biochemical enzymatic cascade. no threshold; modulation of ongoing signal 4 Variable cain: adaptation to changes in light intensity. Contributes to LARGE operating range

How many visual ganglion cells are there?

1 million!

Describe the different functional parts of photoreceptor cells

1 outer segment - located at the distal surface of the neural retina 2 inner segment - located more proximally 3 cell body 4 synaptic terminal

when 1 rhodopsin absorbs 1 photon ---> what happens next?

1 rhodopsin absorbs 1 photon --> all trans -> metarhodopsin II activates 500 transducin --> 500 PDE activated --> 10^3 cGMP hydrolized per second! --> aroudn 250 Nat+ channels close --> 10^6 Na+ ions don't enter (per 1s) --> 1 mV HYPERpolarization!

What are the 3 overarching stages of phototransduction

1. activation of visual pigments by light 2. stimulation of cGMP phosphodiasterase (breaks down cGMP) -> lowering of cGMP concentration 3. Closure of cGMP gated ion channels --> hyperpolarization

Why was it difficult to localize function in the brain?

1. parallel procesing 2. distributed, modular procesing

What 2 events mediate light adaptation?

1. slow recovery of membrne potential (between -70 and -40mV) 2. Desensitization of the receptor (so you'd need more light to stimulate the same change in membrane potential)

Explain the segregation in the LGN of contra/ipsi inputs, and which layers in the LGN are magno vs parvo

1: contra - Magno 2: ipsi - Magno 3: ipsi - Parvo 4: contra - Parvo 5: ipsi - Parvo 6: contra Parvo

human speech frequencies

300Hz to 3KHz lots of frequencies multiple frequencies w/ different amplitudes now what? how do we decode this? we do a fourier transform= permits a common scheme. can take complex frequencies (tones) are conceive of them as the sum of simple frequencies inversely, complex frequencies can be decomposed to constituent simple frequencies

speed of sound

340 m/s very slow! implications: lightning we see light way faster than the speed of sound

Which layers of V1 are input vs output? where do the output layers project to?

4C: main input layer (M and P afferents from the LGN remain segregated in 4C - M--> 4Calpha, P --> 4C beta) V1 output layers: Layers 2/3, 4A and 4B ----> extrastriate cortex Layer 5 --> somatosensory cortex, pulvinar, pons Layer 6 --> LGN, claustrum

Heuristics

Mental shortcuts or "rules of thumb" that often lead to a solution (but not always). not always accurate. typically subconscious

motion parallax

a depth cue in which the relative movement of elements in a scene gives depth information when the observer moves relative to the scene objects closer than objects we are looking at move faster and in opposite direction to observer more distant objects move more slowly and in the same direction as observer

Interblob -> pale stripe pathway in visual system carries what type of info?

contours (orientation

the cochlear nerve fibers terminate in the dorsal and ventral _______ _______ in a __________ organization

dorsal and ventral cochlear nuclei in a tonotopic organization

Where are silent nociceptors found?

in the viscera. this class of receptors is not normally activated by noxious stimulation

how does lateral inhibition help with edge detecting?

it sharpens up our stimulus contrast inhibitory surround -> better separates the two distributions -- "notch filter"

why do people naturally shake their hand following an injury like a hammer blow?

it's reflexive behavior because it may alleviate pain by activating large diameter afferents that suppress the central transmission of noxious stimuli

Explain the overall mechanism of light adaptation via calcium

light --> increased PDE --> less cGMP --> channels close, so calcium doesn't come in, but it's still being extruded by the cell = LOW [Ca2+] this leads to two things: Since calcium concentration is low, it no longer performs its two negative feedback functions of inactivating guanylyl cyclase (which lowers cGMP) and it no longer inhibits the inactivation of photopigment. So, as a result, 2 things happen: 1. increased cGMP production 2. increased speed of photopigment inactivation which leads to more intense light stimulus required

What are the mechanisms by which we have a wide dynamic range for hearing?

parallel pathways: high threshold and low threshold primary afferents. Different populations that encode different parts of the spectrum Adaption Attenuation reflex Efferent neural control

Area 17

primary visual cortex

Rhodopsin

the pigment in rod cells that causes light sensitivity two parts: opsin + retinal

T/F V2 (thick stripes), V3, MT, MST cells respond to retinal disparities.

true direction-selectivity in MST is modulated by the disparity of the stimulus --> motion parallax

T/F hair cells are separate from axons

true hair cells SEPARATE from primary sensory neurons have to go through an extra step of synaptic transmission to get the transduction to happen

agnosia for depth and movement

"blindsight" might not know an object if it's moving Areas 18, 37 on right they can't subjectively track it but consciously can

Where does integration of dorsal and ventral stream information occur?

**Distributed processing :) in V2, MT, STP, and prefrontal cortex 1. horizontal connections in V2 link different stripes 2. some interactions in MT (MT responds to motion of isoluminant stimuli, and chromatic info increases neuronal direction discrimination) 3. STP (superior temporal polysensory) likely area of integration. Receives inputs from both streams (multimodal area) 4. In prefrontal cortex: dorsal stream terminates in area 46 (dorsolateral PFC), ventral stream terminates in areas 12 and 45 (ventrolateral PFC). However there is evidence for neurons responding to both object identity and its location

spinohypothalamic tract

-ANS reflex responses contains the axons of neurons found in laminae I V and VIII of the dorsal horn in the spinal cord. these axons project to hypothalamic nuclei that serve as autonomic control centers involved in the regulation of the neuroendocrine and cardiovascular responses that accompany pain syndromes

The sharpness of the retinal image is determined by several factors. Name them

-diffraction at the pupil's aperture -refractive errors in the cornea and lens -scattering due to material in the light path

Monocular depth cues

-familiar size -occlusion -linear perspective -size perspective -shadows and illumination -motion parallax

modalities

-types of stimuli -submodalities: light, heat, sound, pressure, specific chemicals

What is the threshold of hearing? Describe the impressive sensitivity of our hearing

0.3 nm hair bundle movement wow 0.3 nm ~ diameter of large atom brownian motion = 3nm movement of hair bundle lol wow. we can detect change of <1 part per billion in atmospheric pressure (~20 uPascal (threshold at 4KHz) vs 10^5 Pa (atmosphere) but at the same time we have a wide operating range -> 120 dB (10^6) so we are super sensitive to hearing but also really impressive range

What are the 3 main classes of nociceptors?

1 thermal 2 mechanical 3 polymodal (also silent nociceptors)

Which layers of the LGN get projections from the contralateral eye?

1, 4 and 6

Light adaptation serves 2 important roles in perception: explain them

1. discard information about the ambient light while retaining info about object reflectances 2. to match the small dynamic range of firing in a retinal ganglion cell to the large range of light intensity in the environment (gain change)

Different combinations of receptors encode different odorants. They need to be distinguished in the brain. What are the two ways in which this is performed?

1. each olfactory sensory neuron expresses only one odorant receptor gene 2. each receptor recognizes multiple odorants, each odorant is detected by different types of receptors / each odorant creates a unique pattern of signals to be recognized by the brain!! concentration matters. at higher concentrations, receptors with lower affinity for the odorant can fire, causing a different pattern and therefore a different perceived odor

What are the two hypothesis for how timing-based odor coding works?

1. earliest activated receptors determine odor perception: so the most sensitive receptors for an odorant are activated earliest, and these receptors largely determine odor perception 2. Changes in activity over time allow for encoding different aspects of odor stimuli--possibly for different purposes

MT microstimulation results in what?

1. firing rate of MT cells correclates well with monkey's judgment of motion in random dot displays 2. modifying cell's firing rate alters the monkey's perception of motion (biases the decision towards the stimulated direction)

Different hyper-columns are linked by long-range horizontal connections. Explain the 5 main properties of horizontal connections

1. long range (6-9 mm diameter) 2. intralaminar 3. patchy and reciprocal 4. arise from pyramidal (excitatory cells) and terminate on excitatory (80%) and inhibitory (20%) neurons 5. link neurons with similar functional properties (orientation, direction, CO, OD)

What are the 5 main differences between rods and cones?

1. rods are higher sensitivity to light: night vision. Cones are day vision. 2. Rods have more photopigment - they capture more light. Cones have less photopigment, capture less light. 3. rods have high amplification - single-photon detection. Cones have lower amplification -- need tens/hundreds of photons. 4. rods have low temporal resolution (slow-12Hz) where as cones have high temporal resolution (fast 55Hz) 5 rods are more sensitive to scattered light. cones are more sensitive to DIRECT axial rays.

In the taste cortex, different epochs of activity seem to encode distinct kinds of information. What are the 3 types of info?

1. somatosensory: taste information never present 2. chemosensory: distinct patterns of activation for different taste qualities 3. palatability: hedonically similar tastes (sour and biter) evoked similar responses

List and describe the pre & transduction steps of hearing

1. sound waves compressing up and down vibrate the tympanic membrane- that wiggles back and forth 2. tympanic membrane attached to ossicles bones (malleus, incus, and stapes). these vibrate. they serve as a lever. these bones vibrate. they increase mechanical advantage. they serve as variable gain as well. 3. Oval window vibration -> fluid movement in the vestibular duct.. (the round window will bulge out when the fluid moves b/c of the oval window vibrating). 4. Basilar membrane movement 5. (fluid movement in the tympanic duct, dissipated at the round window) 6. Modulation of hair cell membrane potential (& transmitter release) -> change in afferent fiber firing

Summarize the 2 important roles that "light adaptation" plays

1. to discard information about the intensity of ambient light while retaining info about object reflectance 2. to match the small dynamic range of firing in a retinal ganglion cell to the large range of light intensities in the environment

What are the critical problems the taste system must solve for our survival?

1. will this kill me? 2. will this keep me alive?

light absorption makes 11-cis to turn to what? Then what happens?

11 cis (inactive isomer binds to opsin --> all trans ---> metarhodopsin II

Pierre Flourens

1823 he used brain lesions yikes "all perceptions, all volitions occupy the same seat in these cerebral organs; the faculty of perceiving, of willing merely constitutes therefore a faculty which is essentially one" basically your whole brain does every function

Karl Lashley

1920s to 1950s lesions and learning "mass action: depends on size of lesion" "equipotentiality does not depend on which area" "I sometimes feel, in reviewing the evidence on the localization of the memory trace, that the necessary conclusion is that learning just is not possible" lol termed the engram he was so wrong with mass action and equipotentiality hahah.

Which layers in the LGN project through the parvocellular pathway? Which project through the magnocellular pathway? Which columns are contralateral and which are ipsilateral?

1: contralateral eye: magnocellular pathway 2: ipsilateral eye: magnocellular pathway 3: ipsilateral eye: parvocellular pathway 4: contralateral eye: parvocellular pathway 5: ipsilateral eye: parvocellular pathway 6: contralateral eye: parvocellular pathway

Describe the codes used in the auditory system

1: place code: the fibers are arrayed in a tonotopic map in which the position is related to characteristi frequency 2: frequency doe: the fibers fire at a rate that signals the frequency of the stimulus. frequency coding is particularly important when a sound is loud enough to saturate the neuronal firing rate.

what happens when glutamate is released onto ON bipolar cells? Then what happens when light hits the photoreceptors? (in cones)

2 things: (in the dark, when cones are depolarized and releasing glutamate, it has an inhibitory effect onto the on bipolar cells) so it does these two things to inhibit it: opens a K+ channel (has an inhibitory effect) and it also: activates a G protein (metabotropic) --> activates cGMP phosphodiasterase --> closes cGMP gated channels carrying inward Na+ current SO: then when light hits, the cone gets hyperpolarized and releases LESS glutamate. Therefore glutamate can't do it's normal inhibition. So, light decreases this inhibition of ON bipolar cells --> depolarization of the ON bipolar cell

Which layers of the LGN get projections from the ipsilateral eye?

2, 3 and 5

What's the human range of hearing

20-20,000 Hz

How many rows of outer hair cells are there?

3 rows 1 row for inner

agnosia

= lack of knowledge ex: the inability to recognize familiar objects.

orientation columns in V1

A column in the visual cortex contains neurons with the same orientation preference. They are VERTICAL there is laminar specialization (so differences between laminae in a column) e.g: unoriented cells in 4C, M and P pathways segregate in different laminae, direction selectivity in 4B and 6, etc. so while the columns are organized, the layers still have different specialized features

orientation columns

A column in the visual cortex that contains neurons with the same orientation preference. cortical columns consisting of neurons with the same (or very similar) orientation tuning

audiogram

A graphic representation of the relation of vibration frequency and the minimum sound intensity for hearing

eustachian tube

A narrow tube between the middle ear and the throat that serves to equalize pressure on both sides of the eardrum connects to pharynx equalizes pressure between external ear/environment and middle ear

center surround

A neuron that has a "donut-shaped" receptive field. Stimulation in the center of the receptive field has one effect on the cell; stimulation in the surrounding ring has the opposite effect.

rate code

A neuronal coding principle in which the firing rate of a neuron carries information about the stimulus. It is often associated with neural coding of magnitude (intensity of pressure, stretch, light intensity, or loudness). the system by which information about different frequencies is coded by the rate of firing of neurons in the auditory system (or other systems)

unilateral neglect syndrome

A pattern of symptoms in which patients ignore all inputs coming from one side of space. Patients with this syndrome put only one of their arms into their jackets, eat food from only half of their plates, read only half of words (e.g., they might read "blouse" as "use"), and so on. (page 139)

receiver operator characteristic Curve

A receiver operating characteristic curve, or ROC curve, is a graphical plot that illustrates the diagnostic ability of a binary classifier system as its discrimination threshold is varied.

population code (vision)

A single visual percept is the product of activity of a number of neurons operating in a specific combinatorial and interactive fashion called a population code

ruffini ending

A specialized nerve ending associated with slowly adapting (SA II) fibers that have large receptive fields. stretch deep fiber

Reissner's membrane

A thin sheath of tissue separating the vestibular and middle canals in the cochlea.

fast, sharp pain is transmitted by which fibers?

Adelta fibers that carry info from damaged thermal and mechanical nociceptors

the aperture problem

Although an object moves in one direction, each component edge when viewed through a small aperture appears to move in a direction perpendicular to its orientation. The visual system must integrate such local motion signals into a unified percept of a moving object. Gratings are used to test whether a neuron is sensitive to local or global motion signals. When the grating are superimposed and moved independently in different directions, one does not see the two gratings sliding past each other but rather a plaid pattern moving in a single line, intermediate direction. Neurons in the middle temporal area of monkeys are responsive to such global motion rather than to local motion

Amblyopia vs Strabismus

Amblyopia = difficulties perceiving shape and form Strabismus (crossed eyes) = don't have normal depth perception (stereopsis)

Appercetive vs associative agnosia

Apperceptive agnosia: the ability to match or copy complex visual shapes or objects is impaired. This impairment is perceptual in nature, resulting from disruption of the first stage of object recognition: the INTEGRATION of visual features into sensory representations of entire objects Associative: patients CAN match or copy complex objects, but their ability to identify the objects is impaired. This impairment results from disruption of the SECOND stage of object recognition: association of the sensory Apperceptive agnosia: damage to stage 1 of object recognition: integration of visual features into sensory representations of entire objects Associative agnosia: damage to stage 2 of object recognition: association of the sensory representation of an object with knowledge of the objects meaning or functio

dermatome

Area of skin supplied by a single spinal nerve the body area innervated by a single dorsal root place code is maintained: like ribbon cable

anterolateral pathway

Ascending sensory pathway in the spinal cord and brainstem that carries information about pain and temperature to the thalamus. fibers go and synapse into layer 1 and then go up to thalamus

In hierarchical processing, receptive fields get ______ as you go from lower areas to higher order processing areas

BIGGER! and more complicated. can see the bigger picture. ex: at the LGN they are small, just seeing small dots, contrast, etc of the visual field. by V4 you see bsic shapes and color, and by the time it gets to inferior temporal lobe you have a large receptive field where you see complex features and objects

In V1, do Magno and Parvo project to layer 2/3 blobs or interblobs?

Both! In V1 both M and P inputs to layer 2/3 blobs and interblobs (but P input dominates numberically in 2/3

What is slow dull pain transmitted by?

C fibers that convey signals from polymodal nociceptors

taste cell

Cell located in taste buds that causes the transduction of chemical to electrical energy when chemicals contact receptor sites or channels located at the tip of this cell. microvilli into taste pore, contact chemicals at the epithelial surface other end contacts gustatory neurons electrically excitable: Na K Ca voltage gatedchannels- can generate action potentials

V1 complex cells

Complex cells: orientation specific, NO distinct On-OFF subfields, predominate OUTSIDE layer 4 (this is debated) *Spatially non-linear *Strong orientation specificity ("tuning") *May be "end-stopped" *Monocular or binocular - any location has an equal firing response in terms of orientation - stimulation by dark on light AND light on dark - more of these

Explain the generation of on and off center responses in cones

Cones synapse onto both off-center bipolar cells and also on center bipolar cells So there is dual (opposite) synaptic actions of glutamate on OFF and ON bipolar cells: both excitation and inhibition The glutamate gates open different cation channels: 1) GLu on OFF BC: opens a Na+ Channel (AMPA) 2) GLu on ON BC: opens a K+ Channel (activates a G protein (metabatropic) -> activates cGMP phosphodiesterase --> closes cGMP gated inward Na+ current So when light hits: -decreases excitation of OFF bipolar cells --> hyperpolarization (off center) b/c less Na+ is coming in -decreases INHIBITION of ON bipolar cells --> depolarization (on center) b/c

Depolarization evokes contraction of OHC motor proteins. How does this work?

Contraction/relaxation of OHC moves the basilar membrane via stereocilia attachments to the tectorial membrane. (can't do pull-ups without pull up bar). Amplifies cochlear mechanics. :) In simpler terms: OHC stereocilia go into the tectorial membrane above. it is like it's pull up bar the hair cells contract. they are stuck in the tectorial membrane and basilar. So if they pull up using the tectorial membrane it pulls up the basilar

inner hair cells

Convey almost all information about sound waves to the brain (using afferent fibers)

vestibulo-ocular reflex

Coordination of motion information with visual information that allows you to maintain your gaze on an object while you move.

ocular dominance columns

Cortical columns consisting of neurons that receive signals from the left eye only or the right eye only

Blobs of V1

Cytochrome oxidase CO blobs of V1: 1. receive inputs from the I/K layer of LGN (S cones/blue system) 2. Color processing 3. Monocular, unoriented, low spatial frequency Peglike, cytochrome oxidase-rich, dual-opponent color columns

Explain and diagram primary somatosensory columns

D5, D4, D3, D2 columns (D = digit) they have organization of SA and RA type fibers coming to it. witihin each column you have more segregation: so slowly adapting and rapidly adapting column each of those columns have layers I to VI. so the 6 layers is pretty common across sensory systems layer 4 is input from thalamus

Explain normal development of ocular dominance columns

During normal development layer IVC is gradually divided into alternating sites of input from each eye. The consequences of depriving sight in one eye depend on the timing of eye closure. Closure at birth leads to dominance by the open eye (red) because at this point little segregation has occurred. Closure at 2, 3, and 6 weeks has a progressively weaker effect on the formation of ocular dominance columns because the columns become more segregated with time

cochlear amplifier

Expansion and contraction of the outer hair cells in response to sound sharpens the movement of the basilar membrane to specific frequencies. This amplifying effect plays an important role in determining the frequency selectivity of auditory nerve fibers.

Group ABeta fibers

Group II medium diameter 6-12 uM fast speed - 35-75 m/sec myelinated purpose: mechanoreceptors of skin

Group C fibers

Group IV skinny diamter .2-1.5 um unmyelinated: slow 0.5-2 m/sec purpose: temperature, pain, itch

Taste Transduction

Gustatory epithelial cell depolarization caused by: Salty taste is due to Na+ influx that directly causes depolarization Sour taste is due to H+ acting intracellularly by opening channels that allow other cations to enter Unique receptors for sweet, bitter, and umami, but all are coupled to G protein gustducin Activation causes release of stored Ca2+ that opens cation channels, causing depolarization and release of neurotransmitter ATP 1. Tastants pass directly through ion channels (salty, sour) and depolarize the cell --> leads to action potentials --> calcium coming in and leads to primary afferents or 2. tastants bind to G protein coupled receptors, which activate second messenger pathways to let calcium into the cell (umami, sweet, bitter)

In darkness, cGMP concentration is high or low? What is the Na+ flow in darkness? What happens when light hits the eye?

HIGH! a sizeable Na+ influx through the open channels maintains the cell at a depolarized level of approximately -40mV as a consequence, the cell's synaptic terminal continuously releasees the transmitter glutamate. When light hits the eye: decrease in cGMP: THe light evoked decrease in cGMP results in the clusoure of the cGMP gated channels, thus reducing the inward lfux of Na+ ions and hyperopolarizing the cell hyperpolarization slows the release of neurotransmitter from the photoreceptor terminal, thereby initiating a neural signal

temporal codes

HOW neurons fire: -rate codes: increased stimulus intensity -> increased firing rate -pattern codes: ex: bursting vs steady; onset & offset responses

conductive hearing loss

Hearing loss or impairment resulting from interference with the transmission of sound waves to the cochlea 2 types: 1st scartissue caused by middle ear infection (otitis media) can immobilize the tympanum or ossicles. 2nd a proliferation of bone in the ligamentous attachments of the ossicles can deprive the ossicles of their normal freedom of motion

conductive hearing loss cause

Hearing loss or impairment resulting from interference with the transmission of sound waves to the cochlea lose the cochlear amplifying capabilities.

Ampulla of semicircular canals

Houses the receptors that monitor angular movements of the head. it is a thickened zone of epithelium, it contains the hair cells.

What is the "binding problem"?? What is the proposed solutions?

How is distributed information across multiple cortical areas and parallel pathways integrated to generate unitary percepts? -oscillations and synchronization -attention binds multiple features of an object

stephens power law

I = Kx(S-So)^n n is typically .5 to 1.5 I = intensity of sensation experienced by subject K = constant S = stimulus So= threshold sensation is proportional to stimulus intensity raised to a power; k is a constant not 1 to 1 functions --> same recognition for 1 to 10 as 10 to 100, as 100 to 1000, etc that's why it's logarithmic

Where do the IHC stereocilia project? Where do the OHC stereocilia project to?

IHC are in fluid OHC stereocilia project and attach to the tectorial membrane (it's like its pull up bar). OHC have a muscular contraction and have the membrane to pull up to, which pulls up basilar membrane which allows basilar membrane to move

in the dark, there is lots of cGMP in photoreceptor. What does this mean for the voltage?

In the dark -> lots of cGMP ---> channels are OPEN and Na Flows in (depolarization!!!)

Where does phototransduction actually occur?

In the outer segments of the photo receptors. They have the outer segment that include discs.

How do odor maps transform in the projection to piriform cortex?

Individual odors are distributed and overlapping across piriform cortex (so, NOT an 'odotopic' map) piriform cortex neuron representations are also combinatorial

How is the antagonistic Surround pathway for on-center cell's generated? (in cones)

Inhibitory Horizontal cells reverse the effect of light So when light hits the surround, that cell then inhibits the adjacent ON cell by horizontal cell that connects them Horizontal cells are inhibitory- they release gaba it inhibits the presynaptic terminal of the ON cell, so the on center bipolar cell doesn't get activated SO: when an OFF cell gets activated (so light hits the surround) it's hyperpolarized by light. The horizontal cell is no longer excited, so it hyperpolarizes. and the center cone becomes excited--> that leads to a suppression of the on-center bipolar cell! 1. OFF cell hyperpolarizes 2: horizontal cell is no longer excited, so it hyperpolarizes 3. ON cone gets excited and inhibits BC 4. on center bipolar cell hyperpolarizes and is inhibited

Which layers in the cortex (I to VI) have input vs output fibers?

Input: they all technically have inputs, but the main one is layer IV output: I, II from other cortical structures , V, and VI: to spinal cord and subcortical structures, including the thalamus!!

In the retina: -activated rhodopsin (so in the form of metarhodopsin II) diffuses within the disc membrane where it encounters transducin. What happens from there?

Interaction of transducin with metarhodopsin promotes exchange of GDP for GTP! this leads to dissociation of transducin subunits into an tive alpha subunit carrying the GTP and beta and gamma subunits metarhodopsin II can activate HUNDREDS of additional transducin molecules, thus significantly amplifying the cells response thus the active transducin subunit (transducin bound to algpha GTP) forms a complex with a cyclic nucleotide phosphodiesterase, another protein associated with the disc membrane. This interaction greatly increases the rate at which the enzyme hydrolyzes cGMP to 5'GMP!

Oscillatory mechanisms; how do you build an oscillator?

K+ influex through tip channels -> depoalrization Opens V sensitive Ca2+ channels in soma -> further depolarization ** positive feedback Opens calcium sensitivt and voltage senstivite K_ channels in soma K+ EFFLEX -> hyperpolarization **negative feedback SOO: positive feedback builds something up and up and up and then negative feedback turns it off and if these have slightly different time courses then you have an oscillator! slow kinetics -> slow oscillations fast kinetics -> fast oscillations

Describe the Livingstone and Hubel Tripartite parallel pathway model of motion. Was this correct?

LGN magno -> layer 4Calpha -> layer 4B in the V1 still then -> project directly to the thick stripe (as well as v3 and MT) -> MT -> to the parietal lobe (dorsal pathway) partially, except magno doesn't just project to interblobs but also blobs in V1

What are the 2 main concepts of encoding stimulus modalities?

Labeled lines - percept is dependent on WHICH neurons are activated, not on HOW they were activated adequate stimulus - each class of sensory receptors is specialized to respond to a particular form of energy

Explain the different roles of the layers I through VI in the somatosensory cortex

Layer VI: to the thalamus (output) Layer V: to basal ganglia, brain stem and spinal cord IV: input FROM the thalamus!! important! III and II: To areas 1 and 2 SII cortex I: surface: input from cells projecting up from thalamus

Lesion of LGN parvo or Magno layers affect responses in what percentage of V1 neurons? Why?

Lesion of LGN P or M layers affect responses in 50% of V1 neurons other 50% receive inputs from both

Lesions of either Magno or Parvo pathway affects response in which visual area?

Lesions of either M or P pathway affects response in V4!! ventral pathway includes inputs from both P and M however: lesion of the M (but not P) pathway eliminates responses in many MT cells (motion cells)

explain the difference in sensitivity of M and P cells to these different stimulus features: -Color contrast -Luminance contrast -Spatial frequency -Temporal frequency

M: no color contrast sensitivity P: yes, there is color contrast sensitivity M: high sensitivity to luminance contrast P: low sensitivity to luminance contrast M: low sensitivity to spatial frequency P: high sensitivity to Spatial frequency M: high sensitivity to temporal frequency P: low sensitivity to temporal frequency **Helpful tips: -remember M are for motion detection: so it makes sense they don't respond to color contrast or spatial frequency. And that they are very sensitive to luminance contrast (can detect motion using contrast) and they are sensitive to temporal frequency

Smaller diamter objects activate SA1 more or less strongly than big diamter objects?

MORE srongly rate related to curvature and hence local skin deformation larger diameter objects: -lie in more receptor fields -activate more neurons

Which cells solve the aperture problem

MT cells! An example of local to global processing: component (V1) versus pattern (MT) motion V1 cells respond to the component direction 20% of MT cells respond to the percept (direction of the plaid in the pictures: the first one looks like it's moving up to the left and the middle the opposite. when you superimpose them (the right) they look like the plaid is going upward)

RGCs also come as magno and parvo cells, both on and off center. Explain magno vs parvo cell on/off center differences

Magno: large receptive fields, transient responses to sustained illumination, signal fast changes in the stimulus, incolced in PERCEPTION OF THE GROSS FEATURES AND MOTION OF A STIMULUS parvo: small receptive fields, wavelength specific, INVOLVED IN COLOR AND FORM PERCEPTION AND OF FINE DETAILS OF A STIMULUS

fourier transform

Mathematical tool for converting between time domain and frequency domain SO with hearing- it permits common scheme comples frequencies (tones) are the sum of simple frequencies inversely, complex frequencies can be decomposed to constituent simple frequencies the basilar membrane performs physical fourier transform

RA1

Meissner

SA1

Merkel

T/F the neural code is linearly proportional

NO! intensity must be increased around 10x in order to perceive a doubling of sensation

In the dark, Na+ ions flow ______ the photoreceptor through nonselective cation channels that are activated by ______

Na+ ions flow INTO the photoreceptor through nonselective cation channels that are activated by the secondm essenger cyclic GMP (cGMP)

Light Adaptation Mechanism

Negative feedback (cia calcium) provides variable sensitivity and ameliorates saturation (occurs in the cone) 2 events mediate light adaptation 1. slow recovery of membrane potential (between -70 and -40mV) 2. Desensitization of the receptor (so you'd need more light to stimulate the same change in membrane potential) So in the dark: the cGMP gated channels are OPEN and these let in Na+ and also calcium in the cell, there is an active calcium pump that extrudes calcium to maintain a constant calcium concentration in the neuron. So when calcium normally acts through two mechanism (negative feedback). normally inactivates Guanyly cuclase. GC mediates the formation of cGMP. The other mechanism that calcium does is it normally acts by inhibition the photopigment INACTIVATION (so it makes photopigment active). So what happens, when light hits photoreceptor and cascade of events that leads to closure of cGMP channels, and closure of channels, sodium can no longer come in and neither can calcium. However calcium continues to be extruded by the calcium pump!! so the calcium concentration goes down down down. Reduction of calcium concentration and therefore it cannot perform its 2 negative feedback actions! So! light --> low calcium --> increased cGMP production and increased speed of photopigment INACTIVATION --> more intense light stimulus required to close same number of cGMP gated channels increased cGMP production --> recovery of membrane potential (reopens the channels and sodium can come back into the cell = recovery of potential back to -40) increased speed of photopigment inactivation --> receptor desensitization

orientation selectivity

Neurons in V1 that respond best to an elongated bar of light moving across their receptive field, greatest response to a particular angle that bar lies at.

How many outer hair cells are there to primary fibers?

OHC converge! so around 8 OHC converge to 1 primary fibers

Once sounds are above > 4,000Hz, response if not phase-locked so it won't do a very good job of telling the rest of the brain what the frequency is. So what mechanism does the brain work to encode higher frequencies?

PLACE CODE! The basilar membrane. So at higher frequencies, the basilar membrane serves as frequency analyzer (above like 200 Hz or higher and the volley principle: The theory holding that groups of auditory nerve fibers fire neural impulses in rapid succession, creating volleys of impulses. Cells taking turns firing will increase the maximum firing rate for a group of cells. This allows frequency encoding at frequencies higher than an individual neuron can follow the composite of all of these yields a spatial and temporal summation on postsynaptic cell this allows things to be encoded up until around 4,000 Hz

RA2

Pacinian corpuscle can act like accelerometers steady state unimportant onset and offset responses multi-layered corpuscle response properties largely dependent on corpuscle, rather than the sensory cell itself

Where are taste buds located?

Papillae of the tongue, palate, pharynx, epiglottis, and upper third of esophagus

Brodmann Areas

Patterns of cellular organization in the cerebral cortex cytoarchitecture, 1909 still used today (revised) now often related to the function he literally just looked under a microscope and labeled different cell types

distributed processing

Processing that involves a number of different areas of the brain.

What is the most sensitive mechanoreceptor in the somatosensory system?

RA2 receptor: pacinian corpuscle it is exquisitely responsive to high-frequency vibratory stimuli, and can detect vibration of 250 Hz in the nanometer range

SA2

Ruffini

what receptors provide information about the SHAPE of large objects grasped with the entire hand?

SA2 fibers (Ruffini ending) the slowly adapting deep fibers. they help us consistently feel the pressure/shape of the object in our hand

What is the SII cortex the gateway to?

SII is the gateway to the temporal lobe via the insular cortex. regions in the medial temporal lobe, particularly the hippocampus, are vital to the storage of explicit memory

Area 18

Secondary visual cortex (V2) Hypercomplex cells

critical vs sensitive period

Sensitive periods = periods of heightened susceptibility to modification Critical periods = relevant experience must occur in this period if behavior is to develop normally

Glomeruli explain important features of glomeruli

Sites in the brain's olfactory bulb where signals from the smell receptors converge. each axon only terminates in one glomerulus in each glomerulus, axons of several thousand sensory neurons converge on 40 to 50 relay neurons each glomerulus receives input from one type of odorant receptor patterns of glomerular activation is similar in all individuals and are bilaterally symmetrical in the two bulbs

spiny stellate cells in the visual cortex

Spiny stellate cells: a small layer 4 cells exclusively localized in layer 4 of the visual cortex of many species. It is a small cell with a round soma, radiating dendrites and no apical dendrite. In intracortical staining studies (Gilbert and Wiesel., 1979) it has been shown to correlate with simple RFs The axons can have a branch in layers 5 and 6, but most of the arbor forms recurrent collaterals ascending into layers 3 and 2. Outside of V1 these neurons are rare, for example, they exist in the barrel cortex of the rodent. In other areas of thalamic terminations these cells have different morphology than axons that reach layer 1. The small spiny cells are local neurons forming excitatory synapses onto other spiny cells.

Explain the visual field representation through the visual system

Starting in the eye: the left temporal hemiretina sees the right nasal visual field the left nasal retina sees the left temporal visual field the right nasal hemiretina sees the right temporal visual field the right temporal hemiretina sees the left nasal visual field the temporal hemiretina fibers do NOT cross at the optic chiasm, only the nasal hemiretina fibers do. (so that means the temporal visual fields cross over) so, in the LGN and V1--> they represent the contralateral hemifield in an orderly fashion (retinotopic maps)

Umami receptors

T1R1 + T1R3 heterodimer

Sweet receptors

T1R2+T1R3

Bitter receptors

T2R GPCR subunits

In V4, neurons respond to _____ color and are NOT influence by changes in illumination

TRUE color! when it's influenced by changes in illumination that is performed by more global processing

Weber test

Test done by placing the stem of a vibrating tuning fork on the midline of the head and having the patient indicate in which ear the tone can be heard. conductive loss: sound is heard louder in affected ear mimic by occluding one ear

refraction in the eye

The bending of a wave as it passes at an angle from one medium to another cornea and lens do this!

cornea

The clear tissue that covers the front of the eye

The aperture problem

The fact that when a moving object is viewed through an aperture (or a receptive field), the direction of motion of a local feature or part of the object may be ambiguous. local measurements of motion in early visual areas provide ambiguous information about object motion MT cells respond to direction of the entire shape/motion whereas V1 respond to component (just to what they view as moving in one directoin) the global motion is computed by MT SO: MT cells solve the aperture problem

tuning curve

The function obtained when a neuron's receptive field is tested with stimuli at different orientations; its peak defines the maximum sensitivity of the neuron in question.

middle ear function

The middle ear is separated from the outer ear by tympanic membrane. It is connected to the pharynx by auditory and Eustachian tubes. Also helps to equalize pressure inertia of water is heavy compared to air if sound waves impinged directly on oval window, 99.9% of energy reflected so it's this lever system the ossicles aft as levers - they increase force they decrease surface area: tympanic membrane > oval window that increases relative pressure. net result: 20x increase in pressure

tectorial membrane

The movement of the tectorial membrane with sound waves moves the cilia on the hair cells and affects neurotransmitter release by the hair cells A membrane located above the basilar membrane; serves as a shelf against which the cilia of the auditory hair cells move

Lateral inhibition

The pattern of interaction among neurons in the visual system in which activity in one neuron inhibits adjacent neurons' responses. suppress info on sides to better the primary response of the most important neuron

reflectance

The percentage of light hitting a surface that is reflected and not absorbed into the surface. Typically reflectance is given as a function of wavelength.

border ownership

The perception that an edge, or border, is "owned" by a particular region of the retinal image how local edges belong to objects neurons found to encode the side to which the border belongs. A majority of these neurons coded border ownership and the local polarity of luminance chromaticity contrast the influence of visual stimulation far from the receptive field center indicates mechanisms of global context

microneurography

The process of placing a very fine electrode under the skin to record a single nerve fiber, normally done in the hand A technique for recording human sensory nerve activity using needle electrodes inserted through the skin into a nerve trunk.

volley principle

The theory holding that groups of auditory nerve fibers fire neural impulses in rapid succession, creating volleys of impulses. Cells taking turns firing will increase the maximum firing rate for a group of cells. This allows frequency encoding at frequencies higher than an individual neuron can follow the composite of all of these yields a spatial and temporal summation on post synaptic cell this allows things to be encoded up until raoudn 4,000 Hz

1 inner hair cell -> many primary afferents what physiological implications does this have?

There are a lot of primary fibers for each inner hair cell so that means you can now have different populations of primary fibers some of them can be relatively low threshold (high sensitivity) and others can be high threshold and have low sensitivity if you put those two together (like we have rods and cones responsive to different levels of light) so it means different sensitivity, different dynamic range

Stephen Kuffler revealed that the receptive fields of retinal ganglion cells have functionally distinct subareas. What are the subareas?

These receptive fields have a CENTER-SURROUDN organization and fall into one of two categories on-center and off-center later work demonstrated the neurons int eh LGN have similar receptive fields

Ames room

Trapezoidal room; creates an optical illusion with one large and one small person

Describe the anatomy of the cochlea

Two membranes: basilar (on bottom) and tectorial (on top) that are surrounded by inner ear fluid. Vibrating on the oval window causes the fluid to move, which pulls on the inner hair cells and causes them to 'hear' so it's the scala vestibuli scala media scala tympani

Which receptors are best at encoding high-resolution touch like reading Braille dots?

Type 1 - Surface SA1 for example - Merkel cells. they detect surface and have small receptor fields

In the visual system, describe where these project: Upper 4 C alpha ---> Lower 4 C alpha ---> Mid 4 C with dendrites in 4 C alpha and 4 C beta ----> 4 C beta ---->

Upper 4 C alpha ---> 4 blobs + blobs in layers 2 and 3 lower 4 C alpha ---> interblobs in layer 2 and 3 Mid 4C with dendrites in 4 C a and 4 C beta -> Blobs and interblos in layers 2 and 3 4C Beta ---> blobs and interblobs in layer 2 and 3

mirror box

Used to alleviate phantom limb pain; reflection of present limb appears to be missing limb, can work out complaints

overview of motion perception pathway

V1 -> V2 (thick stripes) -> MT -> MST (dorsal where pathway) V1 -> also directly projects to MT

object perception pathway overview

V1 -> V2 (thin and inter stripes) -> v4 -> IT (inferior temporal) in v1: local edge detection in v2: higher analysis of contours (illusory contours)

if mechanism "x" -> increases gain, then to increase dynamic range what do you do?

VARY the gain that expands dynamic range

What part of the thalamus projects to primary somatosensory cortex?

VPL!

ocular dominance columns

Vertical columns of neurons in V1, all of which respond to stimuli from the same eye.

Explain the path that visual processing takes from the retinae to the visual cortex (in detail :))

Visual processing beings in the two retinae. The axons of the retinal ganglion cells, the projection neurons of the retina, form the optic nerve taht extends to a midline crossing point (the optic chiasm). Beyond the chiasm, fibers from the temporal hemiretinas proceed to the ipsilateral hemisphere; fibers from the nasal hemiretinas cross to the contralateral hemispheres. Beyond the optic chiasm the axons from the nasal and temporal hemiretinas carrying input from one hemifield join in the optic tract, which extends to the lateral geniculate nucleus of the thalamus. The LGN in primates consists of 6 layers, each which receives input from either the ipsi or contra eye. B/c each layer contains a map of the contralateral hemifield, six concordant maps are stacked atop one another. The thalamic neurons then relay retinal info to the primary visual cortex.

Dorsal pathway of vision

WHERE is it pathway magnocellular pathway motion and depth goes from the occipital love dorsally to the parietal lobe

population codes

WHICH neurons are fire ex: labeled lines; touch vs nociception ex: HOW many neurons fire(increased stimulus intensity -> increased number of neurons activated

What are the 4 W's of modality?

What is it? (touch vs vision, pressure vs vibration, identity of object) Where is it? Location hoW is it? Intensity When is it? Timing (duration)

What stimulus properties (of the 4 W's) is the most difficult to discriminate in the auditory system and why?

Where (W) = location we are locating it in 3d space. we use both our ears to locate it. sound is all around us, we can hear stuff around corners even if we can't see it closing one eye you can still make do pretty well with location/depth but closing one ear, you are lost it's hard to locate things. we really depend through binuaral comparisons

length constant

Where the depolarization is 37% of that at the origin. is a measure of how far along an axon an electrical impulse can propagate. Without myelin the insulator, the length constant will decrease.

Jacksonian march

a characteristic sensory seizure there is, in addition to motor progression, a sensory progression. numbness and paresthesia (inappropriate sensation such as burning or prickling) begin in one place and spread throughout the body. ex: might start at finger tipes and spread up hand, arm, etc. happens because of the arrangement of inputs from the body in the somatosensory cortex: the seizure starts in the lateral region of the cortex, in the area where the hand is represented, and propagates across the cortex toward the midline.

"blindsight"

a condition in which a person can respond to a visual stimulus without consciously experiencing it agnosia for depth and movement broadmanns area 18 and 37

representational neglect

a person asked to imagine a scene and then describe it ignores half of the imagined scene but then if you tell them to imagine they are facing the opposite direction they can tell you what they couldn't before, but can't tell you what they did before about the opposite direction. so the information isn't lost, its the ability to create/imagine the info from just one perspective. the info is in their, just not retrieved under present conditions

All experience is a product of what

a product of your nervous system a creative fiction

anterolateral system

a somatosensory system that carries most of the pain information from the body to the brain pain temperature (minor flutter) crosss over at the level which it enters.

conduction aphasia

a speech disorder characterized by the inability to repeat words with intact spontaneous speech production and comprehension; usually due to injury to the arcuate fasciculus

off-center cells fire when

a spot of light in the center of their receptive field is turned off

On-center cells fire when

a spot of light is turned on within a circular central region the surrounding annular region has the oppsite sign. For on center cells, a light stimulus that does not include the center produces a response when the light is turned off, a response termed on-center, off-surround

tip link

a tiny filament that stretches from the tip of a stereocilium to the side of its neighbor when stereocilia bend, it stretches the tip links and makes it more likely for potassium channels to open for K+ to influx and depolarize the cell

ear canal

a tube running from the outer ear to the middle ear part of the external ear resonant frequency of around 3500 Hz limits frequencies that reach tympanic membrane somewhat selective to frequencies

synchrony codes

a type of contextual timing code they involve something about context how a neuron fires NOT in respect to how it fires in respect to itself but also what other neurons are doing at the time of firing ex: are a given neuron group firing in phase or asynchronously in the picture- the firing rate are the same, it's just when it's together/in different patterns

The primary visual cortex constitutes the first level of cortical processing of visual info. From there, info is transmitter over 2 major pathways. Explain where the 2 pathways go and what info they carry.

a ventral pathway to the temporal lobe carries info about what the stimulus is, and a dorsal pathway into the parietal lobe carries info about where the stimulus is, information that is critical for guiding movement

Hierarchial processing in vision

a way that visual information is processed it goes in a hierarchial direction. So it basically starts with lower center to progressively higher areas, like V1 and V4 the receptive fields of neurons (depicted by red circles in pictures) become progressively larger LGN -> V1 -> V4 -> IT LGN: small dots, contrast V1: orientation, retinal disparity, some color V4: color, basic 2D and 3D shape, curvature IT: complex features and objects

How many types of RGC cells exist?

about 20 Retinal Ganglion Cells exist (morphology and physiology)

Explain the end result of the cascade that happens when a photon hits the retina

absorption of a photon by the pigment-protein sets in motion a biochemical cascade that ultimately lowers the concentration of cGMP, thus closing the cGMP gated channels and moving the cell closer to the K_ equilibrium potential. In this way, light hyperpolarizes the photoreceptor.

Explain Stage 1 of phototransduction

activation of pigment molecules by light light absoprtion -> 11-cis (inactive form) into all-trans all trans --> metarhodopsin II then metarhodopsin II performs stage 2

Normally, air conduction hearing is better than bone conduction hearing (they both contribute to our sensitivity). What happens if there is a partial deficit in the middle ear?

air conduction will be worse b/c you don't have amplifier in the middle ear. so then BC > AC

convergent excitation

all neurons in the same receptive field converge to the same second order neuron

describe the properties of sound stimuli compare this to vision and somatosensory stimuli

alternating compression and rarefraction of air: -bidirectional: including below baselines -this has implications! ^^ we don't have negative "touch" but we do have in a sense negative oscillations in sound stimuli ------------------------------------ in somatosensory system: we don't have "negative touch" we go from zero to above zero in terms of pressure. in vision: it's oscilatory but not in the same way. we have transducers that go from above zero to hyperpolarized in the auditory system: we have transducers that both hyperpolarize and depolarize. it matches what's happening in the real world.

Rods respond to dim light, cones do not. Rods connect to rod bipolar cells, BUT rod bipolars do not connect to ganglion cells! So what mediates the response to dim light?

amacrine cells! amacrine cells communicate rod response: -they do so in a coordinated fashion -gap junction: electrical synapse (same sign) -glycine: inhibitory synapse (opposite sign) so how it works: rod photoreceptor inhibits the rod bipolar cell. the rod bipolar cell forms a gap junction (+++) with amacrine cell. The amacrine cell has opposing effect onto the OFF ganglion cells and a positive effect on the ON bipolar cell so amacrine cells inhibit the OFF system by a glycine synapse (-) and amacrine cells excites ON system by a GAP junction! essentially when light hits rod -> you'll have opposite effect on OFF and ON system that info is then passed onto off and on ganglion cells

dorsal column-medial lemniscal pathway

an ascending somatic sensory pathway that mediates information about touch, pressure, vibration, and limb proprioception touch, pressure (SA) flutter, vibration (RA) proprioception crosses over after it synapses in cuneate or gracile nucleus

critical period

an optimal period early in the life of an organism when exposure to certain stimuli or experiences produces normal development

What is pain?

an unpleasant sensory and emotional experience associated with actual or potential tissue damage it is NOT the direct expression of a sensory event, but rather the product of elaborate processing by the brain of a variety of neural signals

describe the characteristics of the apex vs the base of the basilar membrane

apex: -flexible region near helicotrema (distal end) -wide (500um, 5x apex) -thin and floppy LOW FREQUENCIES base: -narrow (100um, 1/5 of apex) -thick -stiff--100x the apex HIGH frequencies

A modern definition of pyramidal cell:

apical and basal dendrites covered in spines, axon that leaves the cortex (to other cortical areas or subcortical structures). These are the output cells of the cerebral cortex. And those with somata in different layers send axons to different sites The only non -pyramidal cell type that sends axons outside of the cortex is the large spiny stellate cells in layer 4B of primate V1.

What are the two type of visual agnosias in humans?

apperceptive agnosia (stage 1 processing normally occurs here) cannot see object parts as a unified whole. UNable to construct sensory representatinos of visual stimuli associative agnosia: (stage 2 processing normally occurs here) cannot interpret, understand, or assign meaning to objects. Sensory representation is created normally but cannot be associated with meaning, function, or utility

Which visual agnosia disrupts the first stage of object recognition?

apperceptive: you can't integrate visual features into sensory representations of entire objects

CO BLOBS are at the center of ____ _____ CO BLOBS align with ______ ______

are at the center of OD bands align with pinwheel centers

perceptive field

area from which sensation seems to arise evoked by nerve stimulation similar to receptive field: skin area that activates neuron

how many inner hair cells are there to primary fibers in the ear?

around 1 IHC to every 10 primary fibers

Explain how the vision is a constructive process

as we move around the shape and size of objects on the retina change as the ambient illumination changes the brightness and spectral content of the image on the retina changes YET we do not perceive the size and shape of objects as changing, and a white shirt looks white in the dark and in bright like the brain makes assumptions as to what it is to be seen in the world; these assumptions are in part learned from experience and in part wired

dorsal column pathway

ascending pathway for somatosensory information; runs through dorsal area of spinal white matter C fibers, Abeta fibers can carry pain and temperature to brain stem and thalamus goes to layers 1, ii, IV, V and then go to thalamus and brain stem

Which visual agnosia disrupts the second stage of object recognition?

associative agnosia: disrupts the association of the sensory representation of an object with knowledge of the object's meaning or function

Describe the length and characteristics of hair cell cilia at the base vs apex of the basilar membrane

at the base: hair cell cilia are short and stiff responds best (moves most) to HIGH frequencies at apex: hair cilia are long and floppy -respond best (moves most) to low frequencies

What has the sensation and pain associated with phantom limb syndrome been attributed to?

attributed to impulses entering the spinal cord from the scar of nervous tissue in the stump. In fact, removing the scar or cutting the sensory nerves just above it may relieve pain in some cases. imaging studies of somatosensory cortex of patients who have lost a hand suggest that phantom limb sensation are caused by a rearrangement of cortical circuits. as the afferents from the lost hand wither, adjacent afferent fiers expand into their place

Contrast the auditory system with the somatosensory system

auditory: -small, separate from primary fibers -many hair cells release transmitter at rest (calcium channels active at rest) -transmitter releas modulated directly in response only 1--uV (like photoreceptors) WITHOUT action potential -sustainable high release rate -net result: -allows modulation rather than threshold -allows bi-directionality -well suited for auditory stimulus: compression and rarefraction

Which cells in the retina have center surround organization?

bipolar cells have center surround organization and are ON center or OFF center -- just like retinal ganglion cells so BP and RGC

If someone speaks like this, what aphasia might they have? "Yes... Monday... Dad and Dik... Wednesday nine olok... 10 oclock... doctors.... and teeth..."

broca's you can probably get the meaning from it but their speech production/expression is awful

taste buds

bunched taste cells, in pappillary troughs papillae -> taste bud -> taste cell -> taste receptor

pattern codes

bursting vs steady; onset and offset response a type of temporal code (how the neurons are activated)

How does pigment epithelium (melanin) in the eye reduce light scatter?

by absorbing light not captured by the retina

Alternative to activity maps, how else can olfactory stimuli be encoded?

by timing or dynamics of neural activity! The next criterion we looked at was whether the dynamics of odor maps evolve within the time-frame over which animals are known to be able to perform odor discrimination tasks. Several studies now have shown that rats and mice can learn to perform simple odor discriminations in less than 200 msec, or a single sniff. In fact, another observation that we made is that, at least at low sniff frequencies, the temrpoal pattern of glomerular activation is actually repeated with each successive sniff. For example, here, can see that, in response to the ester ethyl butyrate, have caudal-lateral glomeruli responding with the shortest latency, followed shortly by these anterior-medial glomeruli. This row of frames shows evolution of response maps over the course of one sniff. Subsequent sniffs in the same odor trial are shown in the lower rows, and what is really striking is that this sequence is actually repeated with surprising precision with each respiratory cycle.

Explain the mechanism behind hair cell adaptation

calcium -> activates calmodulin -> decreases myosin ATPase -> tip link downward migration -> decrease tip link tension -> decrease channel openings

what happens with hair cell depolarization?

calcium influx modulation of transmitter release WITHOUT action potential!! that then releases transmitter to the spiral ganglion neuron which will then have action potentials

What activates polymodal nociceptors

can be activated by high intensity mechanical, chemical, or thermal (both hot and cold) stimuli. This class of nociceptors is found at the ends of small diameter unmyelinated C axons that conduct more slowly, at speeds less than 1.0m/s

surround inhibition

capacity of an excited neuron to reduce the activity of its neighbors. Lateral inhibition sharpens the spatial profile of excitation in response to a localized stimulus. so in this case it's inhibited by periphery, but excited by the middle excitatory center so the 2nd order neuron excited in center of receptive field but inhibited by outer.

spinoreticular tract

carries pain signals resulting from tissue injury contains the axons of projection neurons in laminae VII and VIII. this tract ascends in the anterolateral quadrant of the spinal cord dorsal columns and terminates in the cuneate and gracile nuclei of the medulla

What accounts for the spatiotemporal sensitivity of human perception?

center-surround receptive field of RGCs can account for the spatiotemporal sensitivity of human perception

Explain the generation of OFF center, ON surround (in cones)

central illumination: light --> hyperpolarizes the photoreceptors --> excitatory transmitter stops being released --> bipolar cell hyperpolarized annular illumination: light --> hyperpolarizes the photoreceptors 00> horizontal cells are hyperpolarized --> that stops the hyperpolarizing of photoreceptors --> so the bipolar cells are DEPOLARIZED Think about it: if the surround is ON then the surround will depolarize/be activated by LIGHT HITTING ON IT

receptor potential How is it related to stimulus intensity

change in transmembrane voltage evoked directly by the stimulus often ~logarithmically related to stimulus intensity

The attenuation reflex doesn't do much for the initial bomb explosive sound... lol but what is it good for?

chronic sounds! And for bats ;) it turns down your gain like send/receive in radar or like shooting bullets between spinning propellar blades ;) the continual loud sound is dampened

where does the neural representation of sound begin?

cochlear nuclei. Then to the brain stem. through midbrain and thalamus to the cortex.

P cell role in vision

color vision and vision requiring high spatial and low temporal resolution

Describe the Livingstone and Hubel Tripartite parallel pathway model of color and form is this correct?

color: LGN parvo -> blobs in V1 -> thin stripe in V2 -> v4 -> IT form: LGN Parvo -> interblobs in v1 -> interstripes in v2 -> v4 -> IT partially! except parvo doesn't just project to blobs, but also to interblobs in V1

why does distributed, modular processing make it hard to localize function in the brain?

complex capabilities derive from more elementary operations (modules) the nature of these subcomponents is often counterintuitive: the logical solution is often NOT the biolopgical solution component parts CAN NOT be accurately inferred by introspection iterative boot strapping

Changes in air pressure produce up and down movements of the basilar membrane. Describe the difference between compression and rarefaction and the effect they have on the basilar membrane

compression: Push against the oval window -> pushes fluid in since it's not compressible -> that pushes the membrane DOWN and pushes the round window so it buldges OUT when air is rarefacted b/c it's sine wave (air molecules become less compacted) and tympanic membrane pulls out, it pulls middle ear bones with it, and the membrane moves UP! round window goes in

What does the german term "Gestalt" mean?

configuration or form the central idea of gestalt psychologists it what we see about a stimulus--the perceptual interpretation we make of any visual object--depends not just on the properties of the stimulus but also on its context, on other features in the visual field

what causes referred pain

convergence at dorsal root ganglion this phenomenon occur because a single lamina V neuron receives sensory input from both regions, and thus a signal from this neuron does not inform higher brain centers about the source of the input. as a consequence the brain often incorrectly attributes the pain to the skin, possibly because cutaneous inputs predominate.

transduction

converts stimulus energy into an electrical signal: the common language of the nervous system conversion of one form of energy into another. In sensation, the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brains can interpret.

how does stimulus offset work in pacinian corpuscles?

corpuscle layers return to original arrangement so neuron is re-stimulated

Firing rate of MT cells in monkeys correlates with what?

correlates well with monkeys' judgement of motion in random dot displays

Which cranial nerves relay taste information?

cranial nerves relay taste info to the brain stem: gustatory nerves include both VII (anterior tongue) and IX (posterior tongue) and X (taste buds in throat/mouth not on tongue)

Auditory maps are refined during _____ _______

critical period

The channels Y/M subserve what function?

crude form and motion vision

binocular depth cues

cues of depth perception that arise from the fact that people have two eyes stereoscopic vision is due to the two eyes being horizontally separated by 6cm the brain translates retinal disparities into geometric relations cannot be accomplished until information from the two eyes come together (First in V1) stereo requires binocular cells sensitive to horizontal disparities in the 2 retinal images

Explain what is happening in dark vs light adaptation

dark adaptation: bright light: rods are saturated, cones are active --> Dark: temporary blindness until rods take over light adaptation: Dark: cones are inactive, rods are active ----> bright light: temporary blindness until cones take over

pacinian corpuscle

deep pressure & vibration RA2: rapidly adapting type 2 dermis (deep tissue) stimuli: vibration

When does the cell body of an outer hair cellin the ear shorten, and when does it lengthen?

depolarization of an isolated outer hair cell through an electrode at its base causes the cell body to SHORTEN hyperpolarization causes it to lengthen

Does depolarizing hair cells lengthen or shorten them? What about hyperpolarization?

depolarize HC -> Shorten -> Pulls up basilar membrane hyperpolarize -> lengthens

Sweet taste transduction

detected by a complex of two g protein coupled receptors T1R2 and T1R3 T1R have a large N terminal extracellular domain T1R2 found mostly in foliate and circumvallate papillae (almost always include T1R3 high concentration of sugars can be detected by T1R3 alone

Bitter taste transduction

detected by a family of 30 g protein coupled receptor T2Rs different T2Rs recognize different bitter compounds all t2rs are expressed in a single taste cell this leads to all bitter compounds eliciting the same perceptual quality of bitter some bitter compounds might be recognized exclusively by only one T2R

Outer segment of photoreceptors

detects light stimulus contains membranous discs they contain visual pigments (membrane spanning proteins) --> up to 10^8 molecules/cell purpose of disks (invagination of the plasma membrane) is to increase the membrane surface area

In the cortex, taste responses are dynamic. What does this mean?

different aspects of a taste stimulus are encoded at different times! :)

why bother with multiple sub-modalities?

different mechanoreceptors encode different aspects ("dimensions") of an object and interact with object first contact and other changes accentuated : common theme for sensory systems haptic perception

Explain how the basilar membrane can be described as performing a fourier transform

different parts of the basilar membrane have different stiffnesses and different masses the consequences of those different physical properties at different locations, is that those different locations are differentially sensitive to different frequencies so what this means: dif parts of the membrane wiggle more or less in response to dif. frequencies which in turn causes more or less activation of the hair cell so the basilar membrane is somewhat performing a fourier transform

to be discriminable, different stimuli must activate ______ receptive fields

different receptive fields

IT lesions result in:

disrupt object recognition (you can see object attributes but not recognize the object) - visual agnosias prosopagnosia (can't recognize faces) loss of response invariance (loss of size constancy, position constancy, form cue invariance

MT lesion

disrupt pursuit eye movements in the lesioned part of the visual field (misjudgement of target speed) they also reduce the ability to detect motion in the visual field

submodalities

distinctive subcategories of modalities; (brightness and color for vision) These are distinctions or subset that are part of each representational system that encode and give meaning to our experiences. e.g. A picture may be in Black/White or Colour, may be a movie or still, may be focused or defocused.

inner hair cells ___________ to multiple primary fibers in the auditory nerve

diverge outter hair cells converge but inner hair cells diverge

Range of synaptic divergence and convergence in the CNS

divergence: 1 neuron -> 1-10K neurons!!! convergence: 1 neuron - 10k -> onto 1 neuron! "the number of possible permutations and combinations of brain activity (synapses) exceeds the number of elementary particles int he universe" wow. haha that's just an estimation but wow.

Explain the overview of anterolateral and dorsal column pathways

dorsal column and anterolateral pathway: enter at the dorsal root in the spinal cord the dorsal column goes up the dorsal column until it reaches the medulla where it synapses on the cuneate (upper body) or gracile (lower body) nucleus. then it crosses over in the sensoryd ecussation and goes up the medial lemniscus until it synapses in the thalamus. From the thalamus it goes to the cortex the anterolateral pathway synapses first in the dorsal horn. then it immediately crosses over to the loewr ventral fasciculus and up the anterolateral pathway (spinothalamic tract) until it synapses in the thalamus. From there, it synapses in the cortex and also the dorsal anterior insular cortex to process the emotional aspects of pain Place code is maintained and submodalities are maintained different sets of modalities cross at different levels but both end up int eh same (contralateral) cortex

Signals from nocicpeptors are conveyed to neurons in which part of the spinal cord?

dorsal horn

area 46

dorsolateral prefrontal cortex

attenuation reflex turns ( up or down) your gain?

down

All connections between cortical areas are reciprocal. What does this mean and why is it important?

each area sends information back to the areas from which it receives input these feedback connections provide information about cognitive functions, including spatial attention, stimulus expectation, and emotional content, to earlier levels of visual processing

"adequate stimulus" theory

each class of sensory receptors is specialized to respond to a particular form of energy

labeled line

each neuron can be thought of as a labeled line in which ACTIVITY signals a stimulus with a GIVEN VALUE in the picture: each cell's preferred orientation, the line labe, is represented as a vector pointing in the direction of that orientation. each cell's firing is a "vote" for the cell's line label, and the cell's firing rate represents the weighting of the vote. The cell's signal can thus be represented by a vector pointing in the direction of the cell's preferred orientation with a length proportional to the strength of the cell's reponse. for all the activated cells one can calculate a vector sum with a direction that represents the value of the stimulus

Explain the transduction process from taste cell -> cortex

each taste cell is innervated at its base by peripheral branches of primary sensory axons each sensory fiber branches and innervates several taste cells within numerous taste buds cell bodies lie in the geniculate, petrosal and nodose ganglia peripheral branches travel in cranial nerve VII, IX, and X central branches of gustatorys ensory axons enter medulla, terminate on neurons in gustatory area of the solitary tract. From there, it goes to the thalamus, then to the gustatory cortex :) thalamus also transmits taste info to the hypothalamus *controls feeding behavior* some neurons in gustatory cortex respond to one type of tastant, some multiple types

Early order vision includes the retina, LGN, and V1 encoding. What info do they encode and what still needs to be represented?

early order vision: orientation, wavelength, direction of motion, etc. at each point in space are represented by the time image reaches V1 BUT more global properties of objects, such as their shape, color, motion, and location in the world have not yet been represented

Efferent inhibition _____(increase/reduce)_____ peak responses and disrupts tuning specificity

efferent inhibition REDUCES peak response and disrupts tuning specificity when you turn on efferent stimuli, the oscillation goes away at some frequencies but not others turn efferent stimulation on: peak drops on, but the nonsetter regions go up (sensitivity goes up)

What do sub modalities allow for

encoding of different properties of a given cutaneous object and the body's interactions with it (haptic discrimination)

Why is there a large driving force with hair cell depolarization?

endolymph has high K+ and perilymph has normal CSF so that results in Ek = 0mV Transmembrane V = -120mV so there is a large driving force and henc large receptor potential (25mV) when channels open on the sterocilia, the high K+ endolymph K+ flood into the hair cell (which is located in perilymph).

receptor types are specialized for converting certain types of stimulus ________

energies! hence adequate stimulus. volatile molecules don't activate cutaneous mechanoreceptors light doesn't activate auditory hair cells oscillatory changes in air pressure sound) don't activate photoreceptors

Why do we have center-surround retinal fields?

enhances stimulus contrast, transmit DIFFERENCES (not absolute illumination) contributes to response invariance (luminance is interpreted in context of background)

Broca's aphasia

expressive aphasia patients could understand language, but there were severe disorders in language production (grammar), despite no conventional motor problems content is real, comprehension is normal repitition is impaired non oral outputs are also affected. they can't write. or they can still whistle etc

Weber-Fechner Law

extends dynamic range I = Kxlog (S/So) where I is perceived intensity, S is stimulus strength, So is threshold, and K is a constant

Our capacity to localize sounds in space, especially along the vertical axis, depends critically on the sound gathering properties of the ______

external ear

pinnae

external ears: they collect and direct sound into canal contribute to vertical localization (via differential reflection)

Stria vascularis

external wall of cochlear duct composed of mucosa that secretes endolymph secretes endolymph which has high K+; +80mV

What are the overall functions of the external ear, middle ear, and inner ear?

external: capture mechanical energy middle: transmit it to the receptor organ inner: transduce it into electrical signals suitablefor neural analysis

What are thermal nociceptors activated by? Describe the anatomy of the receptor

extremes in temperature typically greater than 45C (115F) or less than 5C (41F). THey are peripheral endings of small diameter, thinly myelinated Adelta axons that conduct AP at speeds of 5 to 30m/s

IT (inferotemporal cortex) function What do IT recordings show?

face and complex form recognition (invariant representation) IT recordings show: -very large receptive fields, include fovea; no retinotopy (positional invariance) -many cells selective for shape and color -some cells respond to complex shapes (hands or faces)

True / False In V1, there are no connections between blobs and interblobs

false within V1 local neurons make connections between blobs and interblobs

T/F Form, Color, Motion and Depth are all processed in the same area of the cerebral cortex

false! form color motion depth are processed in discrete areas of the cerebral cortex

t/f the thalamus gets more input from the body coming up TO the cortex

false! it gets more info from the cortex to do more top down processing not what we usually talk about though lol

t/f "pain" is just strong touch

false! it is not!

T/F the receptive fields near the fovea are the largest

false! they are the smallest. the receptive fields for retinal ganglion cells that monitor portions of the fovea subtend approximately 0.1 degrees whereas those in the visual periphery reach up to 10 degrees.

Firing rate of neuron may encode stimulus __________ example: mechanoreceptors

firing rate of neuron may encode stimulus intensity increasing stimulis intensity -> increasing channel opening -> increasing channel openings -> increasing GENERATOR POTENTIAL (receptor potential) amplitude -> generator potential -> action potential,whereas receptor potential may not lead to AP

Wernicke's aphasia

fluent / receptive aphasia comprehensive problems

perilymph

fluid that fills the bony labyrinth of the inner ear high Na+ low K+ similar in composition to cerebrospinal fluid

perilymph

fluid that fills the bony labyrinth of the inner ear normal CSF concentrations

endolymph

fluid within the membranous labyrinth of the inner ear Na+ poor K+ rich composition maintained by the action of ion pumps in specialized cells

Endolymph

fluid within the membranous labyrinth of the inner ear high K+ concentration +80mV (relative to perilymph) endocochlear potential

Depth perception does NOT require _____ perception

form perception BUT form can be perceived based exclusively on binocular disparity

Where the basilar membrane is best activiated depends on what?

frequencies! particular frequencies produce maximal motions at particular locations aka: Tonotopy far end has low frequency

Duplex theory of frequency encoding

frequency theory: at LOWER frequencies (< around 4,000Hz), primary afferents discharge in phase with an auditory signal - 1:1 < around 500 Hz phase-locked around 500 Hz to 4,000Hz place theory: at HIGHER frequencies (> than around 200 Hz) basilar membrane serves as a frequency analyzer -in some cases, hair cells themselves are also electrically and/or mechanically tuned so at higher frequencies they don't fire as often b/c refractory but they still tend to fire in the same phase

Describe the central auditory pathways that extend from brain stem to auditory cortex

from cochlea -> CN VIII -> to cochlear nuclei. Some cross the trapezoid body and go up and others stay and go up dorsal acoustic stria. Synapse in the superior olivary nuclei and then some in the nuclei of lateral lemniscus. then synapse in the inferior colliculus in the midbrain. then to the medial genicular nucleus of the thalamus. then goes to the primary auditory cortex

What are the non-retinal inputs to the LGN?

from reticular formation of the brain stem (arousal, sleep) feedback from cortex (v1) controls the flow of information rom the retina to the cortex

What are the other two other pathways that leave the retina that is not the basic pathway that projects to visual cortex?

from the retina: runs to the superior colliculus and is important in controlling eye movement. this pathway continues to the pontine formation in the brain stem and then to the extraocular motor nuclei from the retina: to the pretectal area of the midbrain, where neurons mediate the pupillary reflexes that control the amount of light entering the eyes

Explain the difference between the two types of retinal ganglion cell receptive fields

ganglion cells have center-antagonistic surround receptive fields and come as ON center or OFF center On center: -when light is shone onto center, it excites the ganglion cell -when light is shone onto surround, it inhibits the ganglion cell -when light diffused onto both center and surround: weak response from ganglion cell Off center: -when light is shone onto the center, it inhibits the ganglion cell -when light is shone onto surround, it excites the ganglion cell -when light diffuses on both center and surround: weak responses from ganglion cell

What is the "real job" of the nervous system?

given a neural response, determine what the input is!

Axons terminate on the dendrites of the olfactory bulbs within a bundle of neuropil called _______

glomeruli each axon only termintaes in one glomerulus

What holds the mapping of odorants?

glomeruli! maps of responses to low concentrations of odors, showing singular activation of different glomeruli by different odorants. note bilateral symmetry!

Receptor neurons express a single odorant receptor and converge onto a single _________ in the olfactory bulb

glomeruli! olfactory sensory neurons of a single type converge onto the same glomerulus glomeruli constitue a map of odorant receptors

Group Aalpha fibers

group 1 fat diameter (13-20 um) fastest speed 80-120m/sec myelinated purpose: proprioceptors of skeletal muscles

Group Adelta fibers

group III skinny diameter: 1-5um myelinated medium speed 5-30m/sec purpose: pain, temperature

perception of flavor depends on what 3 inputs?

gustatory, olfactory and somatosensory molecules released from foods or beverages are pumped into the back of the nasal cavity by tongue, cheek, and throat movements somatosensory system is involved in the localization of flavors sensation evoked by spicy, minty, or carbonated things

The cochlear nerve transmits action potentials from the _____ _____ to the _____ ______

hair cells to the auditory cortex

Stereocilia

hairlike extensions on the tips of hair cells in the cochlea that initiate the release of neurotransmitters when they are flexed IHC stereocilia in fluid OHC stereocilia into the tectorial membrane

why does the sensory homonculus (somatotopic map) have systematic distortions?

has size distortions: related to RECEPTOR NUMBER not size of body part. related to receptive field density and size. and perceptual resolution! ex: why cortex dedicated to fingers is bigger than to back has location distortions: due to bifurcations

feature detection neurons

have 2 types of neurons: orientation sensitive neurons and direction sensitive neurons in Area 2 in cortex when a line is in a specific orientation it fires robustly, but other orientations it fires not at all so how do we do that? connect the dots. take receptive fields across the palm in different directions. the ones in the same direction convege to specific post synaptic target. direction sensitive neurons: where the stimulus is directed you get a weak or strong response.

What do the semicircular canals detect?

head rotation

conductive hearing loss

hearing impairment caused by interference with sound or vibratory energy in the external canal, middle ear, or ossicles

sensorineural hearing loss

hearing loss caused by damage to the cochlea's receptor cells or to the auditory nerves; also called nerve deafness

Rinne Test

hearing test using a tuning fork; checks for differences in bone conduction and air conduction so you put it on the back of your hear to test bone conduction and ring it. when you are done hearing it through bone conduction and put it by your ear you can still hear it b/c bone and air conduction are different air conduction -> with middle ear bone conduction -> bypasses middle ear normally AC hearing > BC hearing

what are the 2 ways visual info is processed?

hierarchical processing parallel processing

One channel, X/P to the cortex subserves what function?

high resolution pattern vision

What are the 5 major cell types in the retina

horizontal cells bipolar cells amacrine cells ganglion cells photoreceptors

Which cells in the retina respond to light with graded changes in membrane potentials? Which ones fire action potentials?

horizontal cells and bipolar cells (like the photoreceptors) - no action potentials!! many retinal ganglion cells and amacrine cells fire action potentials

contextual codes

how a given neuron fires in relationship to other neurons ex: synchronously or asynchronously with other neurons for various different stimuli

Contextual codes

how a given neuron fires in relationship to other neurons ex: synchrony among different neurons with different stimuli

errors (visual illusions) are systematic and hence informative of what?

how the nervous system actually operaties the exception that "PROVES the rule"

If someone speaks like this, what aphasia do they likely have? "Indication of measurement in piece of apparatus or intimating the cost of apparatus in various forms"

huh? like have no idea what it smeans speech is fluent, with normal rate and melody unlike broca's, but it jsut doesn't make sense

odorants are detected by a huge receptor family. Which type of receptors? How many ORs do humans have compared to mice?

humans: 389 mice: 1141 they are G-protein coupled receptor it's the largest g protein coupled receptor gene family in the genome! by far!

In the auditory system, what happens when frequency contractions are in or out of phase with the movement of the basilar membrane?

if contractions are IN phase, it amplifies oscillations of basilar membrane if they are out of phase, it attenuates oscillations of basilar membrane

attenuation reflex

if there is a high intensity stimuli for hearing, middle ear muscles then contract. Tensor tympani (to malleus) stapedius (to stapes) This dampens movements (increase joint stiffness; motor system priinciple- contract muscle like bicept, the joint (elbow) becomes more stiff) This decreases sensitivity in summary: Response where onset of loud sound causes tensor tympani and stapedius muscle contraction that's why the second loud noise doesn't startle you as much

explain temperature intensity coding

if we know temperature we know the firing rate right?? but that's not the job of the sensory NS the job of sensory NS is to tell us what's out there in the real world so for a given T, firing rate is predictable.. but for a given firing rate, what was the T?? for any particular firing rate you have to potential temperatures... ONE firing rate indicates TWO different Temperatures so we need another type of code: pattern code!! so we compare temperatures to know the current temperatures also use population code so activating different populations of neurons we can disambiguate the temperature

if you close one tragus, will sounds become louder or softer?

if you close your ear perceived sound intensity would go down right?? in some cases that is wrong. so it depends. typically, softer, (because loss of air conduction amplification pathway) but what if much of the target sound is transmitted via BONE CONDUCTION! closing ear -> less AC sound in -> less inhibition out of hair cells -> LOUDER sound in, via bond conduction to hair cells, not Air conduction (AC)

lesions to temporal lobe

impaired object recognition in patients with bilateral inferior occipitotemporal damage: -can localize objects in space but cannot recognize drawings of familiar objects -cannot recognize short printed words -cannot recognize familiar faces (prosopagnosia) -monkeys with removal of IT (inferior temporal) cortex cannot perform visual discrimination tasks (objects, colors, shapes, patterns), but no impairment in visuo-spatial task

lesions to the parietal lobe cause what deficits?

impaired spatial vision in patients with bilateral posterior parietal damage: -can recognize objects but can't point to them cannot describe locations of objects relative to other objects (agnosia) -hemispatial neglect -monkeys with removal of Posterior parietal cortex show deficits in visuo-spatial performance, but no impairments of visual discrimination tasks

What are the 3 parts of our unconscious mental life

implicit dynamic preconscious unconscious

Signal Averaging

improves auditory signal to noise ratio brownian motion: random average = 0 auditory signal: cyclic, allows temporal averaging of responses over several cycles

In V2, which type of connections are there between the stripes?

in V2: long range horizontal connections within the upper layers connect all stripe types

The concentration of cGMP controls the activity of cGMP gated chnnels in the plasma membrane of the outer segment of photoreceptors. What is happening in the dark? What about light?

in the dark: when the cGMP concentration is HIGH, a sizeable Na+ influx through the open channels maintains the cell at a depolarized level of approximately -40mV. As a consequence the cell's synaptic terminal continously releases the transmitter glutamate in the light: the light evoked decrease in cGMP results in the CLOSURE of the cGMP gated channels thus reducing the inward flux of Na+ ions and hyperpolarizing the cell. Hyperpolarizing the cell slows the release of NT from the photoreceptor terminal, thereby initiating a neural signal.

where does pain and temperature info begin to integrate?

in the dorsal horn of the spinal cord some segregation is maintained, but integration begins here have to integrate body part with the experience of pain

At what stage of processing is the neural representation of space clearly evident?

in the early stages of sensory processing: in primary and higher order areas of somatosensory cortex0 where it takes the form of a map of the tactile sensors on the body surface

where are mu opioid receptors highly concentrated?

in the superficial dorsal horn of the spinal cord, the ventral medulla, and the periaqueductal gray matter, important anatomical sites for the regulation of pain. smart! they are also in lots of other places. their widespread distribution explains why systemically administered morphine influences many physiological processes in addition to the perception of pain.

prosopagnosia

inability to recognize faces area 20, 21 bilaterally brodman areas

cochlear amplifier amplifies auditory acuity. How does an increase in gain like this affect sensitivity? How does increase in variable gain affect range?

increase in gain -> increase in sensitivity so we have really sensitive hearing vairable gain -> increased range (via efferent control) also note that bandwith selectivity of gain -> has effects on frequency tuning

In light adaptation, increased cGMP production leads to what? increased speed of photopigment inactivation leads to what?

increased cGMP production means the channels are open and sodium and calcium can come into the cell. this leads to recovery of the membrane potential back to around -40mV increased speed of photopigment inactivation leads to: the receptor is desensitized so it requires more intense light stimulus

hyperalgesia

increased sensitivity to pain it results from sensitization of nociceptors

Hair cell depolarization directly ________ transmitter release

increases depolarization -> calcium influx -> modulation of transmitter release (withOUT action potential) just releases transmitter to the spiral ganglion neurite which can create AP

What does cortical remapping look like after digist separation?

independent stimulation leads to separation in cortex the area of representation of the hand in the somatosensory cortex changes after surgical correction of syndactyly of digist 2-5

What activates silent nociceptors?

inflammation and various chemical agents dramatically reduce their firing threshold. their activation is thought to contribute to the emergence of secondary hyperalgesia and central sensitization, two prominent pain syndromes

T/F central somatosensory neurons can have both excitatory and inhibitory receptive fields

inhibition typically best seen against an excitatory background so in this figure: showing that if you touch the forearm- you get those neurons firing in high response. but if you touch the wrist, then the forarm neurons are inhibited and response is minimal kind of like winner takes all for neighboring neurons

Are horizontal cells inhibitory or excitatory

inhibitory it inhibits presynaptic terminal of cones -> on center bipolar cells

Where does most of the auditory input come from in the brain? inner or outer hair cells?

inner hair cells 90-95% receive input from inner hair cells

most input comes from the _______ hair cells most efferent control goes to the ______ hair cells

input primarily from inner hair cells (to cochlear nucleus (afferent)) efferent control primarily to the outer hair cells (from superior oliveary complex (efferrent))

the nervous system does not represent entire objects by the activity of single neurons. Instead, how does it work?

instead, some cells represent parts of an object and an ensemble of neurons represents an entire object each member of the ensemble may participate in different ensembles that are activated by different objects. This arrangement is known as a distributed code. distributed codes can involve a few neurons or many. in any case, a DC requires complex connectivity between the cells representing a face and those representing the name and experiences associated with that person

What are mechanical nociceptors activated optimally by?

intense pressure applied to the skin; they too are the endings of thiny myelinated Adelta axons.

Parameters for the visual system

intensity, color, etc.

Explain the interlaminar connections in V1

interlaminar connections integrate activity within v1 from input layers upward to layers 2/3 from layers 2/3 downward to 5 ---> 6 feedback from 6 ---> 4C and 5 ----> 2/3

What is the main function of the sensory nervous system?

interpret stimuli in the real world :)

What controls the eyes ability to have variable apertures?

iris and pupil smaller size -> less light and increased depth of field (squinting)

If you take the corpuscle off of a pacinian corpuscle, what is the result? What does this tell us about pacinian corpuslces and on/off responses??

it basically acts like a slowly adapting receptor. this tells us that the phasic nature is dependent on the pacinian corpuscle itself, not the neuron stimulus onset: slow redistribution of corpuscle layers abbsorbs stimulus force. results in LESS stimulation of neuron. stimulus offset (!): corpuscle layers return to original arrangement. the neuron is re-stimulated

What happens when the basilar membrane moves up and down?

it displaces the hair cell bundles when it moves up-> stereocilia bend OUTward (toward kinocilium) and hair cells DEPOLARIZE when it moves own -> stereocilia bend INward and hair cells hyperpolarize

What happens when you train an animal to spin a wheel *train their digits* What happens when you surgically attach (fuse) two digits?

it leads to expansion of their cortical areas of their finger tips that were stimulated in the task their territory is shaded/shared in the cortex. and the shared area grows as well cortical remapping or-- the skin innervation can be modified in the periphery. now that the two fingers are continuous axons can cross over. axons in digit 4 can go to digit 3. so they are overlapped/rewired if you cut them, the blurring remains. so it shows what establishes borders/what maintains them the mechanism has crossed over for the digits when they were fused

What are some functional advantages of having the visual cortex organized in columns?

it minimizes the distance required for neurons with similar functional properties to communicate with one another and allows them to share inputs from discrete pathways that convey info about particular sensorya ttributes this efficient connectivity economizes on the use of brain volume and maximizes processing speed the clustering of neurons into functional groups like in the columns of the cortex allows the brain to minimize the number of neurons required for analyzing different attributes

Outer hair cell function

it moves the basilar membrane! outer hair cells damage (too much calcium b/c of overdose of antibiotics) lowers the response of the basilar membrane without cochlear amplifier is to get info out of the brain and they react to sounds coming in so they can both protect the cochlea from loud sounds and act as a break so that when sounds come in and get loud the outer cells spread the growth of sound so you can tolerate from low to high.

What happens when glutamate is released onto OFF bipolar cells? Then what happens when light hits the photoreceptors? (in cones)

it opens a Na+ channel (AMPA) so when light hits: decreases excitation of OFF bipolar cells --> hyperpolarization (off center) decreases inhibition of ON bipolar cells (depolarization (on center) SO that's under normal conditions but when light hits: then you decrease excitation of OFF bipolar cells -> hyperpolarization (off center) b/c less sodium is coming through

When efferent inhibition is turned on in the auditory system, what two things happen?

it reduces peak response and disrupts tuning specificity so the efferent stimuli comes on, and the mV go way down. but you also minimize oscillations

In the somatosensory system, there is a pretty standard 1:1 afferent firing. if you have skin indentation of unit 1, then the afferent firing will be around unit 1. Harder indentation, higher frequency indentation. how well would this 1:1 encoding work for the auditory system? Compare and explain

it wouldn't work quite as well because the nature of the stimuli for hearing is much different. There is a wide range of frequencies! up to like 20,000Hz! challenge for frequency encoding: you can't use 1:1 firing b/c neurons can't fire like 20,000 times so you the body engineered a different solution

light receptors are always "on" in the dark. so what's the nature of the response to light in mammalian photoreceptor?

it's a HYPERpolarization! b/c you got positive ions coming through in the dark, -> dark current close the channel in the light so less positive the membrane potential becomes more negative this has huge implications if we are using depol or hyperpolarization or both for our system we can't trigger AP with hyperpolarization so there are other mechanisms

generator potentials

it's a receptor potential that generates an action potential generator potentials are a subclass or receptor potentials some but not all receptor cells have action potentials in sensory cells with action potentials, receptor potentials mamy then be known as "generator potentials" b/c they generate the AP number of AP varies with size of receptor potential; often a linear relationship

Non-spiny, non-pyramidal neurons

largely local inhibitory gabaergic cells in layer 4Cbeta

The larger oscillations in air pressure leads to what effect on the basilar membrane?

larger oscillations in air pressure -> larger oscillations of basilar membrane! Also peak shift with implications for tonotopy) Larger change in hair cell Vm -> larger transmitter release which means larger afferent firing on the primary afferent neuron that goes to the cns

why is surround inhibition/lateral inhibition functionally important?

lateral inhibition enhances stimulus contrast without lateral inhibition, as you go onto relay neurons they have big receptive field and it's pretty difused but if you add in lateral inhibition then the relay neurons get a pretty specific relay neuron stimulus diffuse spell bell shape becomes sharp shape with inhibitory trophs surroudning it. functionally this is imporant because it's easier to discriminate the peak you want than a big blump of activity

Layer 4B input to MT is predominantly M or P type?

layer 4B input to MT predominantly of Magno type SO magno domination of one output pathway (that to MT is the exception not the rule!

Which layer in the cortex (I to VI) gets input from the thalamus?

layer IV (four)

Apperceptive agnosia

lesion from posterior inferior temporal cortex cannot see object parts as a unified whole unable to construct sensory representations of visual stimuli evidence that stage 1 of visual processing occurs here

Associative agnosia

lesion in anterior inferior temporal cortex cannot interpret understand or assign meaning to objects sensory representation is created normally but cannot be associated with meaning, function, or utility evidence that stage 2 of visual processing occurs here

Vision provides us with info about objects as patterns of reflected light. Objects absorb and reflect light. Light objects reflect ________ dark objects reflect ______ colored objects _____

light objects reflect a lot of light dark objects reflect little light colored objects ABSORB certain wavelengths and reflect others, their color is given by the wavelengths of light that they reflect. THE VISUAL SYSTEM TRANSFORMS PATTERNS OF REFLECTED LIGHT AS VIEWED BY THE EYE INTO A MENTAL/COGNITIVE IMAGE OF THE WORLD

Meissner's copuscles

light touch superficial

How are action potential frequency often related to amplitude of generator potential?

linearly

Tonotopic maps

link specific places within the brain to the types of auditory stimuli processed auditory nerve fibers laid out like piano keyboard: -high frequency on one end, low frequency on the other -allows for cochlear neuroprostheses

How are action potential frequency often related to stimulus intensity?

logarithmically

how are generator potentials often related to stimulus intensity?

logarithmically

What happens to the dark current when light hits?

low [cGMP] channels, channels closed, so instead of being at like a -40mV, light hyperpolrizes it more because Na+ channels close and it goes to -70mV

The brain analyzes a visual scene at three levels. What are the three levels?

low, intermediate and high low: visual attributes such as local contrast, orientation, color, and movement are discriminated intermediate: involves analysis of the layout of scenes and of surface properties, parsing the visual image into surfaces and global contours, and distinguishing foreground from background high: involves object recognition

What are the 3 levels of processing?

low-level processing: orientation, color, contrast, the disparity intermediate leel processing: contour integration, surface properties, shape discrimination, surface depth, surface segmentation, etc high level processing: object identification.

M cells have lower or higher spatial and temporal resolution than P cells?

m cells have LOWER spatial sensitivity than P cells and m cells have HIGHER temporal resolution than P cells

magno -> _______ pathway parvo -> ________ pathway

magno (parasol ganglion cells) goes the dorsal or parietal pathway parvo (midget ganglion cells) goes the ventral or temporal pathway

What percentage of RGCs are magno vs parvo

magno only 8% whereas parvo are 80% other 2 is probably K fibers

What percentage of RGCs are magno and parvo and other?

magno: 10% parvo: 80% non-m or p: 10%

ear bones

malleus (hammer) → incus (anvil) → stapes (stirrup)

What are the superficial touch receptors? what are the deep fibers?

meissner's corpuscles and merkel cells ruffini endings and pacinian corpuscles

What is the mechanisms by which you shut off the cGMP Ca+ cascade once it's been activated by light in the eye?

metarhodopsin II is inactivated through phosphorylation by a specific rhodopsin kinase followed by binding of soluble protein ARRESTIN active transducin (transducin bound to alpha GTP) also has an intrinsic GTPase activity which eventually converts bound GTP -> GDP. Transducin-alpha-GDP then releases phosphodiesterase and recombine with transducin-beta-gamma, ready again for excitation :) once this happens, cGMP concentration is RESTORED by a guanylate cyclase that produces cGMP from GTP. At this point the membrane channels open, the sodium current resumes and the photoreceptor depolarizes back to its DARK POTENTIAL

Explain stage 2 of phototransduction

metarhodopsin activates G protein transducin! activated pigment reduces cGMP metarhodopsin II --> opsin + all-trans retinal --> retuded to all-trans retinal (vitamin A) --> back to 11-cis retinal + opsin again.

List some of the mechanisms that contribute to hair cell sensitivity

middle ear accessory structures temporal and spatial signal averaging specialized extracellular environment of apical and basal faces -> endocochlear potential multiple hair cell specialization in transduction motor proteins as cochlear amplifiers

what determines extent of ocular dominance columns?

minor difference in proportion of differences in input **ocular dominance can be experimentally induced by transplantation

V4 lesions in monkeys vs humans

monkeys: reduced ability to discriminate patterns and shapes. Only subtle color discrimination is impaired (color constancy is impaired too) In humans -> Achromatopsia. (total color blindness). NO defects of shape and texture perception **there is some debate that monkey and human V4 not the same areas

Why do we have center-on and center-off cell groups?

more sensitive to rapid increases or decreases in illumination on center: give strong responses to small increases off center: give strong responses to small decreases Hence, they increase the dynamic range of the system a study used APB: APB blocks the on system --> impaired detection of rapid increases (but not decreases) in illumination

explain how convergence of relay neurons produces direction sensitivity

move in certain directions you get excitation or inhibition first. so that encodes where it is b/c your body knows it's excitation on top, and inhibition on bottom. not strong response if you move across in a non sensitive direction (on the picture if you move up left to right

Parallel processing pathways in visual system

multiple things going on and being processed at a time: ex motion, depth, color and form the main 2 parallel pathways are the where/action pathway and the what/perception pathway where/action (dorsal) detects motion and depth and what/perception pathway (ventral) perceives color and form

near cochlear spiral = _____________________ distal to cochlear spiral = ______________

near = low sensitivity and spontaneous rate distal = high sensitivity and spontaneous rate

Where in the eye is the opponent process theory correct?

neural level of color vision processing :) - so at the level of the retinal ganglion cell the trichromatic theory operates at the receptor level and the opponent processes theory applies to the subsequent neural level of color vision processing

outer hair cells

neurons in the organ of Corti; serve to amplify and sharpen the responses of inner hair cells

Neurons in different layers have distinctive receptive field properties. How do sizes of receptive fields compare between the superficial layer of V1 versus the deeper layer neurons?

neurons in the superficial layer of V1 ahve small receptive fields whereas depper layer neurons have large ones

Hebb's postulate

neurons that fire together wire together postsynaptic cells are more likely to fire when sets of multiple presynaptic neurons fire together consequently -> segregated groups and sharp borders

Is there a single language center in the brain?

nope it's complicated broca's, wernicke's and arcuate fasciculus that connects them are the main areas

pacinian corpuscles increasing frequency of electrical stimulation -> __________ frequency of perceived vibration

normally activated by vibratory stimulus increasing frequency of electrical stimulation -> increased frequency of perceived vibration

Why does closing one tragus/closing your ears make certain sounds (like chewing a cracker) seem louder?

normally you have some inhibition coming down from brain stem to ear. so what triggers that inhibition? the presence of noise. when your ears are open you have soudn energy coming in and brain sends inhibition out. that works on both bone conduction and also on middle ear air conduction but closing your tragus -> you reduce sound in on that ear, but you also reduce the inhibition coming out from brain. so if you're doing this via bone conduction you don't hear it through middle ear but you have bond conduction. so when you talk your voice vibrates some of what you hear from your voice is vibration through the bone that's why your voice sounds different on a recording b/c you remove the bone conduction part haha. SO: you send out inhibition normally. but if you reduce inhibition by closing tragus, but if the only sound that's generated is going through bones, you reduce bone conduction inhibition on one side, but don't reduce it on the other side. so the other side is left uninhibited haha stimuli coming in causes response, but also causes inhibition down. that inhibition is gonna work on the hair cells themselves. if your educe that inhibition it'll get louder and esp for the bone conduction stuff too!

What is the 2nd messenger in phototransduction? What does it do?

nucleotide cGMP acts as 2nd messenger cGMP OPENS cGMP-gated ion channels (mainly Na+) in the dark -> lots of cGMP -> channels are open and Na flows in (depolarization so when there is light nd cGMP phosphodiesterase is activated, it breaks down cGMP which lowers cGMP concentration. That closes cGMP gated ion channels which leads to hyperpolarization

bone conduction

occurs as the eardrum vibrates and causes the auditory ossicles of the middle ear to vibrate the conduction of sound to the inner ear through the bones of the skull

serial processing in the visual system

occurs in the successive connections between cortical areas, connections that run from the back of the brain forward

parallel processing in the visual system

occurs simultaneously in subsets of fibers that process different submodalities such as form color and movement

Eye specific segregation is maintained in V1 layer 4C in what is called...?

ocular dominance columns

flavor is a combo of what 3 things?

olfaction, gustation, and somatosensation

on-center/off-surround

on center cells fire when a spot of light is turned on within a circular central region. The surrounding annular region has the opposite sign. For on center cells a light stimulus that does NOT include the center produces a response when the light is turned OFF, a response termed on-center, off-surround. referring to a concentric receptive field in which stimulation of the center excites the cell of interest while stimulation of the surround inhibits it

What percentage of inputs to the LGN are from the retina?

only 10-20% wow!! Non retinal inputs to the LGN: from reticular formation of brain stem (arousal, sleep) Feedback from the cortex (from V1) those control (gates) flow of information from retina to cortex

Which part of the cortex is a site for FLAVOR integration?

orbitofrontal cortex integration of olfactory and taste information (e.g. flavor): orbitofrontal cortex integrates multimodal information related to flavor -olfactory and taste cortices also interact via amygdala and other limbic centers

V1 Complex Cell Receptive Fields

orientation specific, no distinct on/off subfields, predominate outside layer 4 they respond to orientation of stimulus and also respond to position of stimulus

Roughly how many outer hair cells are there compared to inner hair cells

outer hair cells: around 15K inner hair cells: around 3.5K

Compare the threshold amplitude of the different SA1,SA2,RA1,RA2 etc

pacinian corpuscle RA2 is basically like the human range-- gives us exquisite resolution!!! different receptor types cover different frequency domains of the human threshold :) different receptor types have different threshold ~1000x

spinothalamic tract

pain and temperature the most prominent ascending nociceptive pathway in the spinal cord. it includes axons of nociception specific, thermosensitive, and wide dynamic range neurons in laminae I and V through VII of the dorsal horn these axons cross the midline of the spinal cord at their segment of origin and ascend in the anterolateral white matter before terminating in the thalami nuclei.

phantom pain

pain or discomfort felt in an amputated limb

referred pain

pain that is felt in a location other than where the pain originates

anasthesia dolorosa

pain that occurs without a peripheral stimulus this syndrome can be triggered following attempts to block chronic pain

neuropathic pain

pain that results from direct injury to nerves in the peripheral or central nervous system and is often accompanied by a burning or electric sensation

Area 5

parietal cortex

What is intermediate-level visual processing concerned with?

parsing the visual world into contours and surfaces that belong to objects and segregating these elements from the background this is the most challenging job the visual system must perform

Tripartite model of V1 to V2 of feedforward projections Was it correct?

partially correct, partially wrong: the magno and parvo pathways from the LGN remain segregated in V1 and beyond V1 in particular, parvo inputs from LGN terminate in 4Cbeta, then go to layers 2 and 3 where they contact blobs and interblobs. The blobs project to thin stripe. the interblobs from layer 2,3 project to interstripe. thin stripe and interstripe project to V4 where they are still segregated. then they end up in the temporal lobe (ventral pathway). For magno: they proposed it goes from LGN to V1 layers: 4Calpha, -> then to layer 4B, then there is a direct output to the thick stripe (v2) and also to V3 and to MT (specialized in motion signals), from MT -> to parietal lobe (dorsal pathway)

color constancy

perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object

perceptual constancy

perceiving objects as unchanging (having consistent lightness, color, shape, and size) even as illumination and retinal images change perceptual constancy in the response of IT neurons (the graphs). Area IT are the first area to show perceptual constancy some parts: -size constancy -position constancy -form cue invariance

"labeled lines" theory

percept is dependent on WHICH neurons are activated, not HOW they were activated stimulate cochlear nerve -> hearing stimulate somatosensory neuron -> touch rubbing eyeball -> "sight" microneurography: experimental documentation and higher res understanding

sensitive periods

periods of heightened susceptibility to modification known as sensitive periods occur at particular times in development

maximal displacement of traveling audio wave varies with frequency. The shape of the wave also changes. High frequences have sharp edges, low frequencies have diffuse edge which resutls in por discrimination. So how does one discriminate at low frequencies?

phase locking mechanism with frequency rate code! frequency theory: at LOWER frequencies (< around 4,000Hz), primary afferents discharge in phase with an auditory signal - 1:1 < around 500 Hz phase-locked around 500 Hz to 4,000Hz

Excited rhodopsin activates a ___________________ through the G protein transducin

phosphodiesterase activated rhodopsin, in the form of metarhodopsin II, diffuses within the disc membrane where it encounters transducin, a memer of the G protein family

Explain the process of taking rhodopsin in the 11-cis retinal stage all the way to metarhodospin II and back

photon hits and turns the cis-11 to all-trans. That quickly turns into metarhodopsin I which turns into metarhodopsin II. Metarhodopsin II activates G protein transducin. Metarhodopsin II --> opsin + all-trans retinal. All trans retinal (vitamin A). Then goes back to 11-cis retinal + opsin and back to 11-cist retinal rhodopsin

What are the rules of thumb for the neural code What are the implications of these?

physiological responses: -generator potentials often related to stimulus intensity LOGARITHMICALLY -action potential frequency often related to amplitude of generator potential LINEARLY therefore, action potential frequency often related to stimulus intensity LOGARITHMICALLY implications: -retain sensitivity to relative differences in stimulus stretch -extend dynamic range, despite severe limits on upper frequency of action potential firing (< few hundred Hz, sustained)

3 types of cones in primates, each containing a different ______

pigment! each pigment optimized for absoprtion of light in a different part of the visible light spectrum visual pigment = cone opsin + 11-cis retinal 3 different types of 1/cone types S cones: !0% of all cones and are absent in the central fovea

Where do projections from the olfactory bulb go to?

piriform cortex, the amygdala, the contralateral side of the cortex via the anterior commisure, the hippocampus

somatotopy

point-to-point correspondence between an area of the body and an area of the CNS the nervous system maintains an orderly representation of body surface

increase in number of neurons activated is an example of which type of code?

population code neurons previously silent surrounding the input also get activated if the stimulus is strong enough

Area 7

posterior parietal cortex

accessory structures in the ear are involved in ___-_______ process and provide _______

pre-transduction processes (like amplification/channeling the sound waves to the right place) they provide gain

merkel disk receptor

pressure and texture superficial

Describe the anatomical specialties that the hair cell afferent synapses have. What does this contribute to?

presynaptic dense body: -prominence + close association with release apparatus suggests involvement withunusually rapid release in response to minimal stimulation presynaptic density: short fuzzy rows intramembranous particles: in register w/presynaptic density. Includes Calcium channels maybe? so this may contribute to rapid release rate which contributes to why our hearing is so specialized/sensitive

piriform cortex

primary olfactory cortex major olfactory area mitral and tufted cells from excitatory synapses with pyramidal cells modulated by inhibitory inputs of GABA ergic interneurons modulated by excitatory input of neighboring pyramidal cells

Areas 1-3

primary somatic sensory cortex

How does depth perception work?

problem: how to transform a 2D retinal image inot a 3D image? 1. Monocular depth cues -familiar size -occlusion -linear perspective -size perspective -shadows and illumination -motion parallax 2. Binocular depth cues -stereopsis

Briefly describe the system that allows our eyes to stay focused when we move

projections from the vestibula nuclei to the oculomotor system allow eye muscles to compensate for head movement by moving in such a way as to hold the image of the external world motionless on the retina

Papillae

protrustion on tongue surface papillae -> taste bud -> taste cell -> taste receptor

changing the frequency of stimulation does NOT change the _______ of the stimulus

quality ex: stimulating a touch neuron at higher frequency doesn't make it painful just b/c it's more intense increasing frequency of stimulation doesn't result in 'pain" changes paramter value, not submodality, of perceived stimuus

saccades

quick eye movements from one fixation point to another we focus on key points this prevents us from staring at the same space and our photoreceptors getting bleached it's not conscious

Which touch receptors detect on and off stimuli

rapidly adapting ones like meissner corpuscle and pacinian corpuscle

What are the rapidly and slowly adapting mechanoreceptors for touch?

rapidly adapting: Meissner's and Pacinian corpuscles slowly adapting: Merkel cells and Ruffini ending

Olfactory receptor cells are ciliated. Where are the olfactory receptor proteins located?

receptor cells are ciliated, with the olfactory receptor proteins themselves located on the ciliated terminus of the cell

Are receptor projections to glomeruli asymmetric or symettric?

receptor projections to glomeruli are stereotyped and bilaterally SYMMETRIC

Red light excites ____ cones more than ___ cones whereas green cones excite _____ cones more

red light excites Long (L) cones more than Medium (m cones( whereas green activates M cones

Explain stage 3 of phototransductin

reduced cGMP closes cGMP-gated ion channels ----> photoreceptor hyperpolarizes (b/c Na+ don't enter)

parallel processing

redundancy: brain and biology often has more than one solution to a single problem hence: resistant to damage (lesions, gene knock outs, etc) there's almost always one way to acomplish the same goal in the brain. SO if you knock out a region and a function still continues it's incorrect to assume that area doesn't participate in that function because something else does it if area a canont

Hypercolumn

region of cortex containing a full cycle of right and left eye OD columns and at least a full cycle of orientations arising from any given region of space. This is the processing unit of module of V1 A 1-millimeter block of striate cortex containing two sets of columns, each covering every possible orientation (0-180 degrees), with one set preferring input from the left eye and one set preferring input from the right eye.

SII responds to ______ properties of stimuli

relative

When stereocilia bend towards the shortest stereocilia what happens? (INWARD bending)

relaxes the tip links -> closes channels -> hyperpolarization it's basically the LACK of depolarization, not the actual cl- flowing in or anything

perception of brightness and color relies on what

relies on contrast and thus is influenced by the contrast between objects and their surroundings

Verbal output, repetition ability, and comprehension for broca's, wernicks' and conduction aphasia

repitition is impaired for all of them verbal output is fluent in wernickes and conduction but not brocas comprehension is impaired in wernicke's, but not brocas and conduction

If a limb is severed, why does stimulation of the face eventually evoke responses in the area of where the missing limb is? ex: why does phantom limb syndrome happen in the arm/hand when you stimulate the face

representation of the face, where innervation remained intact, expanded into the adjacent area of cortex that had represented the hand before deafferentation. As a result, stimulation of the face evokes responses in the area of cortex that normally represented the hand. these changes occurred in a wide area of cortex: a third of the entire body ma was taken over by new connections from the face! this happens because neurons can be rewired by experience.

in the PNS, SI respond to _________ properties of stimulus

respond to ABSOLUTE properties (ex: it's 22Hz) not that it's smaller or bigger than something whereas SII responds to RELATIVE properties. ex: if a stimulus is bigger than a separate stimulus

Pacinian corpuscles

respond to deep pressure and vibration deep fiber

Most cells in MT are direction selective and organized into columns and maps. What do they respond to?

respond to moving luminance defined edges respond to moving texture or color defined forms (so sensitivt to color although not color-selective)

Ruffini endings

respond to stretch (fire to constant pressure) SA2: slowly adapting type 2 deep (in dermis) stimulus: skin stretch

Color selective cells in the retina, LGN, V1 and V2 respond to?

respond to wavelengths reflected by a surface in their receptive field's center

Weber's Law

retains relative sensitivity Change in S = KxS K = DeltaS/S size of thedifference threshold (just noticeable difference, JND) is often proportional to the size of the standard :) the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount)

where/action pathway

retina -> LGN -> V1 from V1 -> V2 -> MT -> parietal lobe (dorsal pathway)

what/perception pathway

retina -> LGN -> V1 -> V2 -> V4 -> temporal lobe (ventral pathway

forced-choice discrimination task

rewarded for picking the correct stimulus compared to another so in dealing with SII-- which is sensitive to higher/lower relative frequencies, for example an animal would be rewarded for picking higher frequency stimulus

In hand amputees, why does tapping their face or bicep illicit sensation in the missing limb?

rewiring of the brain! neurons from the face in somatosensory neuron (growth cone) attach to new areas of skin face and hands are right next to each other in the somatosensory map

Describe the anatomy of rhodopsin and how it works

rhodopsin, the visual pigment in rode cells, has two components. The protein portion: opsin, is embedded in the disc membrane and does NOT by itself absorbe visible light. THe light absorbing moiety, RETINAL, is a small molecule whose cis isomer is covalently linked to a lysine residue of opsin absorption of a photon by retinal causes it to flip from the cis to the all-trans configuration. this reaction is the only light-dependent step in vision.

Describe the mechanism of how photons activate and change rhodopsin

rhodopsin, the visual pigment in rode cells, has two components. The protein portion: opsin, is embedded in the disc membrane and does NOT by itself absorbe visible light. THe light absorbing moiety, RETINAL, is a small molecule whose cis isomer is covalently linked to a lysine residue of opsin absorption of a photon by retinal causes it to flip from the cis to the all-trans configuration. this reaction is the only light-dependent step in vision. the change in shape of the retinal molecule causes a conformational change in OPSIN to an activated state called metarhodopsin II. this is unstable and splits within minutes, yielding opsin and free ALL TRANS RETINAL the all trans retinal is the transported from rods to pigment epithelial cells, where it is reduced to all trans retinal (vitamin A), the precursof of 11 cis retinal which is subsequently transported back to rods.

what did phrenology have right vs wrong?

right: structure/function relationships DO exist. Size of neural circuit CAN be related to its importance. Size of neural circuit CAN be modified be experience wrong: brain convolutions NOT reflected in skull. Specific structure-function relationship was fanciful, not based on empirical evidence-- NOT SCIENTIFIC. location idea was right, but they had labeled things totally wrong (exx: small area for langauge... lol)

Rod system vs cone system

rod system: low acuity (no rods in fovea, highly convergent pathway). Achromatic (one type of pigment- no color) cone system: high acuity (cones in fovea, low convergence 1:1). Chromatic (3 types of cones with different pigment-- they see color!

Umami taste transduction

savory taste of monosodium glutamate thought to encourage ingestion of protein G protein coupled receptors: T1R1 and T1R3. they are complex and activated by glutamate concentrated in the fungiform papillae

What are the compartments of the cochlea? What fluid is in them?

scala vestibuli is on top and it has perilymph in the middle is the scala media on top of the organ of corti. scala media contains: endolymph And then below that is the scala tympani below the basilar membrane. tympani contains: perilymph the reissner's membrane separates the scala vestibuli from scala media. the basilar membrane separates scala media and scala tympani

IT recordings respond to complex shapes (hands and faces), but they do NOT respond to:

scrambled faces with same components other complex natural objects (hand) IT "face" cells do respond to conjunction of facial features. Association of mouth and eyes is essential for cell's response

What retinal features are maintained in the LGN?

segregation of afferents from the two eyes segregation of M, P and K pathways retionotopy receptive fields are center-antagonistic surround and receptive fields are ON center or OFF center

What are the five receptor organs in the vestibular apparatusm of the inner ear?

semicircular canals (head rotation) 1. anterior vertical 2. posterior vertical 3. horizontal Otolith organs (linear motion) 4. utricle 5. saccule

Meissner's corpuscles

sensitive touch receptors in the dermis RA1: rapid adapting, type 1 superficial detects lateral motion

Summarize high-level encoding processing (what's the job of the nervous system? how does it do this?)

sensory nervous system job: need to encode attributes of stimuli in the real world with the 4 w's (where, what is it, hoW much is it, when is it) multiple different receptor types, to respond to and encode qualitatively different stimuli (modalities) also allow us to encode different aspects of stimulus and interactions with stimulus (submodalities) there are multiple encoding strategies: different constraints. Can be disambiguation: eg: Pacinian Corpuscless use rate code to encode frequency so having additional codes and receptor types help to encode intensity so all in all this is an impressive biomachine :) We have exquisite sensitivity, yet wide dynamic range covered

What does hair cell transmitter release modulate?

sensory neuron firing so the hair cell transmitters don't create AP, but they create potential on the sensory neuron and that can fire and go to CNS firing AP

taste cells

sensory neurons, apical ends toward taste pore! ** there are 30-100 taste cells per taste bud receptors confined to apical microvilli electrically excitable don't have axons-> contacted by gustatory afferents form chemical synapses with afferent fibers

taste buds

sensory organs in the mouth that contain the receptors for taste have taste pores at the surface which make contact with the tastant contain approximately 100 taste receptor cells contain elongated support cells short lived and replaced continuously by stem cells

parallel processing

separate modalities, features, and quantities are processed separately the processing of many aspects of a problem simultaneously; the brain's natural mode of information processing for many functions, including vision. Contrasts with the step-by-step (serial) processing of most computers and of conscious problem-solving.

Explain the experiment that showed MT lesions reduce the ability to detect motion in the visual field

show dots moving in certain direction. so what was the % correlation in pre and post lesion post lesion: much higher correlation needed in order to perceive direction of motion

V1 simple cell receptive fields

simple cells: orientation specific, distinct ON and OFF subfields, predominate in layer 4 (this is debated tho) -were first mapped in a cat by Hubel and Wiesel -can be constructed by combining the inputs of many center-surround receptive fields from the LGN of the thalamus -are selective for the orientation of a bar of light

SA1 help encode the _____ and ______ of objects touching the hand

size and shape slowly adapting type 1 cells larger diameter objects-lie in more receptive fields, activate more neurons

contour saliency

smooth contours tend to pop out from complex backgrounds

Explain the coding phenomenon by which the response of an auditory nerve fiber can be different when responding to different sound frequencies

so looking at the graph: response to a low intensity sound is this bell shape on the frequency map (basilar membrane doesn't just respond to one frequency at one place, there is a small range for each frequency/location on BM) but then if you do a high intensity sound, the bell curve is bigger and frequences you didn't respond to with the low intensity sound you now do. So: rate code: increase firing rate of given neuron POPULATION CODE: increase number of neurons firing which is what happened in this case

which tastes use ion channels?

sour, salty

What are the receptors or each of the tastes?

sour: proton receptors Salt: sodium transporter sweet: receptors g couple protein receptors: T1R2 and T1R3 like a NT receptor umami: T1R1 and T1R3 mGluRs bitter: T2Rs sweet and umami combine in particular subunits fat: GPR120? K channel? (don't know for sure

posterior parietal damage can cause ____- ______

spatial neglect extrapersonal space can be messed up too so if they have to copy pictures this is what it looks like

Otoacoustic Emissions

spontaneous or evoked sound waves produced within the ear by the cochlea and escape from the ear An otoacoustic emission is a sound that is generated from within the inner ear.

Saccdic masking

stand in front of a mirror; look from eye to eye you do not "see" during saccade (prevents smearing) the nervous system HIDES the movement it also HIDES the HIDING!! OUR sensory system filters stuff out to make the world make sense. cool

What's the first step in solving the puzzle of neural function?

start with givens/observables: worked forward from input (sensory systems) work backwards from output (motor systems) measure response from stimulus code (stimulus) decode (response)

What are the two competing coding schemes of how taste quality encoding works? How would you test this to figure it out?

starts with taste cells. They aren't neurons, just individual sensing cells and synapse on primary afferent neurons that go to the brain. two competing coding schemes: labelled lines where each taste cell is dedicated to a certain taste. across fiber pattern is that each taste cell can code multiple tastes, but they have different amounts so it would be like a sweet cell even if it can detect some salty. in C, it says each cell still only has one receptor, but they would contact primary afferent fibers in a mixed way. so that's why b and c are similar, they have across-fiber afferents to figure it out: see where the receptors are segregated across taste cells. So record from one of the fibers and give the different tastes and see if it only responds to one taste or multiple. Or if you can label them based off of what receptors are.

Border of blob -> thick stripe pathway carries what type of info in the visual system?

stereo/motion

V1 has blobs and interblobs What anatomical feature does V2 have?

stripes they are both anatomically and functionally specialized

What is system's neuroscience?

study of nervous systems functions that emerge from the operations of systems of neurons consideration of how these functions emerge from cellular and molecular underpinnings

What pepptides are released as cotransmitters by many nociceptors with unmyelinated axons?

substance P CGRP somatostatin galanin

Blob -> thin stripe pathway carries what type of info in the visual system?

surface properties color, brightness, low spatial frequency

Bitter receptors are NOT expressed in the same cells as ______/______ receptors

sweet / amino acid receptor so we know that each taste cell does its own taste so we know b is wrong

Which tastes use G protein coupled receptors?

sweet bitter umami

What are the 5 fundamental tastes and what needs to they relate to

sweet: calories (carbs) salty: water homeostasis, neural function umami: calories (protein) sour: spoilage bitter: toxicity

What is the basic answer for how we go from independent pixels with different receptive fields and different submodlaities, do a unified percept of an object with size, shape, pressure, texutre, abstraction, meaning, etc?

synapses! in the CNS we have neurons that have tons of synaptic interactions.

orientation maps in V1

tangential! systematic shift in orientation preference across the surface of V1. full cycle of orientation present in 800uM of v1 WOW!

What are the 3 main types of neural codes

temporal codes population codes contextual codes

ventral pathway of vision

the "WHAT" is it parvocellular-interblob pathway: Form and depth parvocellular-blob pathway: color goes from occipital lobe ventrally to the temporal lobe

Summarize the function of SA1, SA2, RA1, RA2 systems

the SA1 system provides high-fidelity info about its spatial structure that is the basis of form and texture perception The RA1 system conveys info about motion of the object in the hand which enables us to manipulate it skillfully RA2 receptors transmit info about vibration of objects that allows ut to use them as tools The SA2 system provides info about the hand conformation and posture during grasping and other hand movements

contrast sensitivity

the ability to detect differences in light and dark areas in a visual pattern contrast sensitivity = 1/contrast threshold the visual system has band pass behavior.. becomes low pass in dim light

haptic perception

the active exploration of the environment by touching and grasping objects with our hands it relies on an interplay between exploratory movements and the sensory consequences of those movements

receptive field

the area of skin that activates sensory neuron receptor density & RF size related to two point discrimination

Retinal blind spot

the axons of the photoreceptors and blood vessels exit in the optic disk optic disk = blind spot axons and blood vessels exit and enter here no photoreceptors no vision we aren't aware of our blind spot - perception is an active process!!

The basilar membrane at the apex of the human cochlea is more than five times _______ as at the base thus although the cochlear chambers become progressively _____ from apex to base, the basilar membrane _______ in width

the basilar membrane at the ape is more than 5x as broad as at the base the cochlear chambers become progressively LARGER from apex to its base, the basislar membrane DECREASES in width

in the visual system, are the "center" or "surround" areas on the ganglion cells more powerful?

the center and surround areas are MUTUALLY inhibitory. So mutally powerful lol when both center and surround are illuminated with diffuse light there is little or no response conversely a light dark coundary across the receptive field produces a brisk response

Describe the distribution of rods and cones

the central fovea contains no rods but is densely packed with small cones. A few millimeters outside the fovea rods greatly outnumber cones. All photoreceptors become larger and more widely spaced toward the periphery of the retina. The S cones make up only 10% of all cones and are absent from the central fovea.

The LGN and V1 represent the ____contra or ipsi____ hemifield in an orderly fashion??

the contra! b/c the nasal hemiretina crosses over, but the temporal retina doesn't. SO you see the opposite temporal visual field and the opposite nasal visual field

attenuation reflex

the contraction of muscles in the middle ear, resulting in a reduction in auditory sensitivity

What are the deeper layer neurons, such as those in layer V, specialized for? (visual system)

the deeper layer neurons are selective for the direction of movement, and are specialized for the tracking of objects in space

Phrenology

the detailed study of the shape and size of the cranium as a supposed indication of character and mental abilities.

When stereocilia bend towards the TALLest stereocilia what happens? so OUTWARD bending

the distance between tips stretch and channel more likely to open potassium channels open potassium flows in, and the membrane potential depolarizes. this is unique compared to other neurons b/c usually it's Na+ that flows in to depolarize it

In the eye, where is the highest density of photoreceptors, bipolar cells, and ganglion cells?

the fovea! aka the area of retina near the optical axis-- where vision is sharpest and corresponds to the center of gaze that we direct toward the objects of our attention

Approximately how many rods and cones are the the human retina

the human retina contains approximately 100 million rods and only 6 million cones the cells are differently distributed.

The dark current

the inward sodium current that occurs in photoreceptors in the dark (steady depolarization) cGMP gated channels are kept open K+ selective channels are open as well and it flows OUT active pump keeps the Na+ and K+ stable by extruding Na and K+

response constancy

the job of the sensory system is to interpret the real world, not the stimulus energies that impinge upon the nervous system in the real world, the bottom panel is indeed intrinsically lighter (its actual property) but presently in shadow (an incidental temporary feature) the nervous system interprets the actual property, not the temporary state of illumination

two point discrimination

the minimum distance necessary for two stimuli to be perceived as separate the ability to recognize or differentiate two blunt points when they are simultaneously applied to the skin

Feeback projections are thought to provide a means whereby higher centers in a pathway can influence lower ones. How does the number of neurons projective from the cortex to the LGN compare to the number of input to the cortex from the LGN?

the number of neurons projecting FROM the cortex to the LGN is TEN FOLD the number providing input to the cortex from the LGN! Crazy although this feedback projection is obviously important, its function is largely unknown

what is the site of mechanoelectrical transduction in the cochlea?

the organ of corti :)

explain the organization of human dermatomes

the organization seems perplexing when we are standing up but when we look at the human from bent over/four-legged it makes more sense haha (quadrupedal position)

From the LGN, describe the magno and parvo pathways to the visual cortex and which layers they synapse in

the parvo and magnocellular pathway both have output from the LGN that goes to both the ipsi and contra layers of the cortex Magnocellular pathway synapses in IVC alpha (4C alpha) Parvocellular pathways synapse in IVC beta (4C beta) layers 1, 4, and 6 of the LGN (contralateral) synapse in the contralateral column of V1 Layers 2, 3, 5 (ipsi) synapse in the ipsilateral column in V1

After the cascade of activation happens during phototransduction, what is the mechanism that shuts off the cascade?

the photoreceptor's response to a single photon must be terminated so that the cell can respond to another photon. Metarhodopsin II is inactivated through phosphorylation by a specific rhodopsin kinase followed by binding of a soluble protein arrestin, which blocks the interaction with transducin once the phosphodiesterase has been inactivated, the cGMP concentration is restored by a guanylate cyclase that produces cGMP from GTP. At this point the membrane channels open, the Na+ current resumes and the photoreceptor depolarizes back to its dark potential

Where in the eye is the trichromatic theory correct?

the photoreceptors! there are different types of cones that respond to the 3 different types of light/wavelength

Explain how the retina is inverted

the photoreceptors, the cells that actually detect the light are at the BACK of the retina and the other cells are in front of it light must pass through cell layers shifting of inner layers at foveola -> more direct pathway to photoreceptors pigment epithelium (melanin) reduces light scatter by absorbing light not captured by the retina

blind spot

the point at which the optic nerve leaves the eye, creating a "blind" spot because no receptor cells are located there the brain fills it in, adding reasonable inferred information from around.

What are the three somatic sensory cortex divisions?

the primary SI the secondary SII the posterior parietal cortex

Light adaptation

the recovery of the eye's sensitivity to visual stimuli in light after exposure to darkness

lateral inhibition

the reduction of activity in one neuron by activity in neighboring neurons

receptive field

the region of the sensory surface that, when stimulated, causes a change in the firing rate of that neuron

What happens to a cell's response if light covers both the center AND the surround?

the response is much weaker than for center only illumination ex: a bright spot on the center of an ON cell combined with a dark annulus on the surroudn elicits very strong firing

gate theory

the suggestion that only a certain amount of information can be processed by the nervous system at a given time the theory that the spinal cord contains a neurological "gate" that blocks pain signals or allows them to pass on to the brain the relative balance of activity in nociceptive and non-nociceptive afferents might influence the transmission and perception of pain. in particular-- activation of non-nociceptive, sensory neurons closes a "gate" for central transmission of nociceptive signals that can be opened by the activation of nociceptive sensory neurons. "rub the hurt"

What are superficial layer neurons specialized for in the visual system?

the superficial layer neurons are specialized for high resolution pattern recognition

size constancy

the tendency to interpret an object as always being the same actual size, regardless of its distance they're the same size the room is just skewed so it tricks our brain as stimulus distance varies, retinal stimulus changes, but subjective experience remains constant brain calculates distance and automatically adjusts acocrdingly

Where is nociceptive information from the spinal cord transfered to?

the thalamus

opponent process theory

the theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision. For example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green trichromatic signals from the cones feed into subsequent neural stages and exhibit 2 major opponent classes of processing 1. spectrally opponent processing *(red vs green, yellow vs blue) 2. spectrally nonopponent processes: black vs white

Retinal ganglion cells

the third layer of retinal neurons whose axons leave the eyeball and form the optic nerve. These are the first that actually fire action potentials! Gangloin cells have center-Antagonistic surround receptive fields and come as ON-center and OFF-center

Describe the different cell types in the layers of the visual cerebral cortex

the visial cerebral cortex consists of 6 layers pyramidal cells in all layers EXCEPT 4C (pyramidal are output, and 4C is input) Spiny stellate cells are the local neurons of layer 4 (simple RFs), contact other spiny cells. Only those in layer 4B are output cells. Aspiny stellate cells, non pyramidal = largely local inhibitory (GABAergic cells)

What's the main difference between rods and cones?

their sensitivity to light! rods can signal the absorption of a single photon and are responsible for vision under dim illumination such s moonlight. But as the light level increases toward dan, the electrical response of rods becomes saturated and the cells cease to respond to variations in intensity cones are much less sensitive to light; they make no contribute to night vision, but are solely responsible for vision in daylight. their response is considerably faster than that of rods. primates only have 1 type of rod, but 3 types of cones.

trichromatic theory

theory of color vision that proposes three types of cones: red, blue, and green one can match all of the visible colors by mixing any 3 primary colors, as long as mixing 2 of them doesn't produce the third

Illusions are not results of random "mistakes" but of what?

there are more a systematic result of heuristics that are often-- but not always-- correct "mistakes" occur under specific unusual circumstances (ex: 2D not 3D)

Which cells detect and transduce odorants?

there are several types of cells in the olfactory epithelium, but the olfactory receptor neurons are the ones that detect and transduce odorants

if a tree falls in a forest and there is no corresponding neural activity, is there sound?

there is no "sound" ;)

Is a given patch of skin innervated by more than one dorsal root? Or just one? what does this mean clinically?

there is overlap! so a given patch of skin is innrevated by more than one dorsal root damage to a single dorsal root does not produce sensory loss in dermatome anesthesia requires interruption of several successive dorsal roots

Combinatorial patterns of odorant receptor activation are mapped how?

they are mapped into combinatorial patterns of glomerular activation in the olfactory bulb

relay neuron receptive field

they have an excitatory field and inhibitory field and an overlapping area

What do cells in the MST (medial superior temporal area) respond to?

they respond to more global aspects of motion (full field motion useful for optic flow)

Explain the calcium concentration feedback mechanism in photoreceptors that can shut off/restore the cGMP Ca+ cascade once it's been activated by light hitting the retina?

this is mediated by a change in the calcium concentration in the cell calcium ions enter the cell through cgmp=gated channels and are extruded by rapid cation exchangers in the DARK: in intracellular calcium concentration is HIGH in the cell's LIGHT response: when cGMP gated channels close, the calcium levels DROP quickly to a few % of the dark level rhodopsin phosphorylation is accelerated through the action of calcium binding protein recoverin on rhodopsin kinase, thus reducing activation of transducin. SOO: the affinity of cGMP gated channel is increased through the action of calcium-calmodulin ^^ALL of these effects promote the return of the photoreceptor to the dark state

Explain the color-opponent PARVO cells vs Achromatic MAGNO cells

this mechanism (3 different opponent processes) do occur at the POST synaptic cell (retinal ganglion cell) So the 3 are: 1. Red ON/Green OFF, but also Red OFF/green ON --> excitated inputs from L+ (long wavelength) and opposing signals (inhibitory from green and red) in the surroudn(combo of both). SO when this cell excited by diffused light, it responds as nonred cell, and is suppressed by green light. The red off, green on cell looks the same but it says L- in the center. 2. Green ON/Red OFF, but also Green OFF/Red ON 3. Blue ON/Yellow OFF, but also Blue OFF/Yellow ON magno: achromatic: 1. ON center (L+/M+) in center and L-/M- in surround 2. OFF center (L-/M-) center so they receive opposing inputs

How do opiates regulate nociceptive transmission at synapses in the dorsal horn? (explain the 2 mechanisms)

through two main mechanisms: 1. they increase membrane K+ Conductances in the dorsal horn neurons, hyperpolarizing the neurons and thus increasing the threshold for activation 2: by binding to receptors on presynaptic sensory terminals opiates inhibit the release of neurotransmitters and thus decrease the extent of activation of the postsynaptic dorsal horn neurons. the decrease in NT release appears to result from a decrease in calcium conductance and consequent reduction of calcium entry into the sensory nerve terminal.

Explain how extracellular environments of apical and basal faces contribute to sensitivity in hearing

tight junction between the apical and basal side allows you to have two different solutions endolymph bathes apical faces (scala media). this is a special solution, secreted by stria vascularis. high K+, +80mV the perilymph bathes the basal faces (scala tympani) this is normal csf have two separate compartments. presence of tight junction allows us to have two different solutions which allows us to have really big transmembrane potential which in turn allows us to have big receptor potential which allows us to have high sensitivity :) SO to summarize: -unusually large potential (around 140mV) across HC membrane -> -large driving force, inward current, and receptor potential (25mV) -enhanced sensitivity

What's the overall effect of the middle ear??

to match the impedance of the air outside the ear to that of the cochlear partition, thus ensuring the efficient transfer of sound energy from the first medium to the second

Beyond V1, what is the primary task of the visual system?

to represent more global aspects of the image local information (wavelength, orientation) is ambiguous you need higher order processing: ex: which bits of contour and surface go together (belong to the same object)-- image segmentation, figure ground segregation also need to infer true brightness/color of an object independent of overall ambient illumination (brightness/color constancy) also has to determine overall pattern of motion in the visual field (pattern motion/global motion)

Explain the central taste pathway from tongue -> Cortex

tongue -> brainstem -> limbic circuits: hypothalamus & alaygdala brainstem also --> to thalamus --> cortex for perception CN VII, IX, and X carry info to the solitary nucleus of the brain stem from there, some projections go to the VMP of thalamus --> insuli and parietal cortex also from the solitary nucleus, projections go to hypothalamus and amygdala

frequency tuning

tonotopic mapping of frequency in the basilar membrane and organ of Corti if contractions are IN phase, it amplifies oscillations of basilar membrane if frequencies are OUT OF phase, attenuates oscillations of basilar membrane

efferent neural control of the auditory system is

top down control

Merkel cells

touch receptors SA1: slowly adapting type 1 superficial detects edges, points

What are different solutions that the nervous system employs when taking all different types of energy and making it come out as hearing, vision, touch, etc?

transduction (& pre-transduction) different types of receptor anatomy, location, numbers decussations codes used

Contrast hair cell specialization in auditory system with the visual system

transduction mechanism -direct, mechanical -bidirectional -NOT biochemical cascade -unlike photoreceptors *these are all how the auditory system function compared to visual

how to recall implicit memory

trick question- you can't really do it consciously implicit memory is recalled only in performance and not typically reached through conscious recall ex: think about patient HM

T/F sensory processing often involves efferent feedback to CNS and periphery

true

T/F some V1 neurons respond to horizontal retinal disparities (near, far, zero)

true

T/F your ear emits sound

true b/c the round window gets vibrated as well

T/F distinct regions of the brain have different critical periods of development

true not all brain circuits are stabilized at the same time

T/F best response to difference in light intensity in the center and surround is as a contrast detector, not just responding to absolute illumination

true! constrast rather than absolute illumination is what the RGC use to tell us what we are seeing

T/F The Nervous system interacts with virtually all other organ systems

true! it interacts with pretty much every organ so it's starting to be importantant to look at the NS in diabetes and other disease

T/F Everything depends on what brain areas are active and NOT on what activated them

true! we can restore function by adding what's missing can also ameliorate dysfunction by removing what's present but shouldn't be: ex phantom pain from missing hand, tinnitus ringing in ears

T/f action potential firing frequency is often related logarithmically to stimulus intensity

true! hence an intensity code

t/f receptive field size is NOT constant

true! in your back the field size is huge, in our fingers we have tiny receptive fields

on cell vs off cell

turned ON by light off cell is turned OFF by light, and turned on when light turns off SO: if light intensity is suddenly increased -> ON cells fire more rapidly, while off cells fire more slowly or cease firing in the light. THen, when light intensity diminishes again, the ON cells fire LESS and the OFF cells fire more.

type 1 vs type 2 touch cells

type 1 = superficial layer = merkel and meissner type 2 = deep = ruffini and pacinian

representational neglect

type of unilateral neglect where the Pt cannot mentally imagine things that are their left side; can't imagine to move to their left side suggests: memory of external space is perceived in relation to the vantage point of the observer, not simply of that of objects in the environment

Role of the corpus collasum in vision?

unify the perception of objects spanning the vertical meridian by linking the cortical areas that represent opposite hemifields

If a patient has a lesion in the lateral intraparietal area, what syndrome will they most likely have?

unilateral neglect the lateral intraparietal area (in the interparietal sulcus, is involved in representation points in space that are the targets of eye movements or reaching. patients with lesions of parietal areas fail to attend to objects on one side of the body

Why is the nervous system unique compared to other systems in the body?

unlike most other organ systems, does very little work (has other things do the work) the primary function is acquisiton, processing, and storing of information function expressed through regulation of OTHER organ systems

How would you test which taste theory is correct looking at the cortex?

use calcium sensitive dyes that tell you about neural activity present stimuli and look at what kinds of taste they respond to so in this data set, they look like cells are narrowly tuned so it looks like it's labelled lines. Looks like certain cortex only responds to umami and L-ser This is the same group that showed labeled lines early. BUT someone else repeated this certain experiment imaging from taste cortex and found that low and behold, they reported different results. it seems to be an even distribution of cells responding to tastes and that different areas respond to different types of tastes. and you can also record spikes electrophys where it's the cross-afferent fiber theory.

Useful information in visual images is contained in the pattern of _______ rather than in the ______ amount of light reflected by objects

useful info in visual images is contained in the pattern of CONTRASTS rather than in the absolute amount of light reflected by the object (latter depends on the intensity of the light source)

Is air conduction hearing or bone conduction hearing more efficient?

usually AC hearing > BC hearing because you have amplifier in middle ear. so without amplifier they'll be like the same.

what do the two otolith organs sense?

utricle and saccule sense linear motion (translation) b/c gravity is a linear acceleration, the otolith organs also sensethe orientation or tilt, of the head relative to gravity

Where does higher analysis of form and color occur?

v4 v4 cells selective for orientation, form/shape TRUE color, not color that is influenced by changes in illumination

area 12 and area 45

ventrolateral PFC

What receptor type is activated the most for the following stimuli on the skin: vibration pressure tapping

vibration: Pacinian corpuscles (ra2) pressure: SA1: Merkel tapping: RA1: Meissner

M cell role in vision

vision requiring low spatial and high temporal solution (movement)

Binocular vision

vision using two eyes with overlapping fields of view, allowing good perception of depth.

What happens to ocular dominance columns when you deprive one eye during critical period?

visual deprivation of one eye during a critical period of development reduces the wiedth of the ocular dominance columns for that eye!

What do visual illusions show?

visual illusions (misreadings of visual information) show how the brain applies assumptions about the visual world to sensory information it receives

Movement of basilar membrane is a _______ rather than a point

wave it also allows spatial averagin g ifj

Why was the LIvingstone and Hubel Tripartite parallel pathway model of vision incorrect?

we now know that both M and P inputs go to BLobs and Interblobs instead of just P going to blobs and M going to interblobs so, M and P segregation is not fully maintained beyond V1 they were also incorrect in what they assumed to be the laminar origins of these spatialized pathways. in particular they said they blobs (superficial layers 2/3) and interblobs project to Thin and interstripe. but -- in 2002 it was shown that all stripe types in V2 receive input from both layers 2 and 3, and layer 4b even if it's in different proportions. layer 2/3 project to thin stripe -> v4 interstripes project to both pale and thick stripes from both 2/3 and 4B NOW we have the quadripartite scheme (4 pathways from V1 to V2)

What are possibilities for how we encode neural stimuli? Which types of neural codes are there?

we use/read temporal codes: -rate code: ex: increased stimulus intensity -> increase firing rate -patter codes: ex: bursting vs steady; onset and offset responses can also use population code: -which neurons are firing (labeled lines; touch vs nociception) -how many neurons fire (increased stimulus intensity 0> increased number of neurons activated can also use contextual codes: -how a given neuron fires in relationship to other neurons: ex: synchrony among different neurons with different stimuli

What are the 4 W's of the sensory system?

what is it? (modality: touch vs vision) and submodality (pressure vs vibration, identity) Where is it? location hoW much is it? Intensity (weak/strong) When is it? Timing (eg duration)

serial processing (hierarchial)

what puts it all together? occurs when the brain computes information step-by-step in a methodical and linear matter primary SN -> primary sensory cx, simple cells -> primary sensory Cx, complex cells -> unimodal sensory cx: puts features together -> multimodal sensory cx: puts modalities together (areas of the brain that integrate auditory, visual and tactile information for example to create big process)

SII is sensitive to "higher/lower" relative frequency. explain what that means

what this means is that it doesn't respond to the fact that something is specifically 22Hz.... but responds that if 22Hz is higher or lower than another frequency experiences.

when is 22Hz NOT 22Hz in the brain?

when the brain is responding to relative properties and concepts (ex: higher or lower)-- not to primary stimulus attributes

when picking and lifting up an object, explain when each receptor types are activated (RA1 RA2 SA1 and SA2)

when the hand first makes contact, the rapidly adapting cells (Meissner and Pacinian) fire rapidly. when you start to lift, the Pacinian fire again. the SA1 and SA2 are slowly activated when and during the time you are holding the object and slowly turn off when you contact the table and set the item down. When you release the object your rapidly adapting ones fire rapidly again signaling "off" merkel and ruffini help you keep constant pressure (SA1 and SA2)

In one influential study, Hubel and Wiesel raised a monkey from birth to 6 months of age with one eye lid sutured shut. What were the results?

when the sutures were removed, it became clear that the animal was blind in the deprived eye. They then performed electrophysiological recordings from cells along the visual pathway to determine where the defect arose they foudn that RGC in the deprived eye, as well as neurons in the LGN responded well to the visual stimuli and had normal receptive fields in contrast, cells in the VISUAL cortex were fundamentally altered! in the cortex of normal animals most neurons are binocularly responsive. in animals that had been monocularly deprived for the first 6 months most cortical neurons did not respond to signals from the deprived eye! the few cortical cells that were responsive were not sufficient for visual perception not only had the deprived eye lost its ability to drive most cortical neurons, but this loss was PERMANENT and irreversible.

population codes for neural sensory codes

which neurons fire as oopose to how a neuron is firing ex: labeled lines; touch vs nociception; hot vs cold OR how many neurons are firing ex: increased stimulus intensity -> increased number of neurons activated

barrel cortex, mouse whiskers

whisker map in mouse's brain if you cut off whisker, the neuron next to the neuron associated with the whisker that was cut off will become more sensitive (type of neuroplasticity) this is how we know it happens in humans

Do olfactory receptor cells have axons?

yes! they project through the cribfriform plate to the olfactory bulb

Explain the Quadripartite scheme Is this accurate?

yes, this is accurate to our knowledge! Blob thin pthway: surface properties: color, brightness, low spatial frequency border-thick pathway: stereo/motion interblob-pale pathway: contours (orientation) all stripe types receive input from layer 2/3 and layer 4B except pale medial. THey don't receive input from 4b.

How does adaptation contribute to "wide dynamic range" in the auditory system

you can lower or raise set point to alter when you can fire. So for example when firing: -initial phasic increase -reduction of tonic firing to plateau -turn stimulus off- post offset below baseline there is some sort of adaptation you change your set point. if you lower set point (below zero) you don't fire anymore you have adaptation occurs in transduction. rightward shift, without change in shape or amplitude implies shift in range of sensitivity (set point)

Explain why it makes sense that different spinal laminae receive different inputs

you not only need to know that you are in pain, but need to know where so pain and temperature: goes from Adelta fibers to the thalamus through the anterolateral pathway and C fibes and Abeta fibers carry a similar message but up to the brain stem and thalamus through the dorsal column pathway

Which taste theory is correct?

you record from different afferent fibers to see if they are each just one taste or if they are excited by multiple 3/4 respond to just one taste, and about a quarter respond to others so by and large this suggests a labeled line model happening. So the labelled line model seems to be the most correct but recent research does show that taste afferents work (mostly) as an across fiber patterns! others did the same experiment and didn't find the same results. When you increased concentration then they become a lot less narrowly tuned.... so another study showed the system is working as across fiber system. so it's a controversy :) you should also look in the brain/cortex where the taste perception is actually happening. when people looked at mice brains it looked like labeled lines and that certain areas of cortex are only sensitive to sweet or sensitive to umami, etc. when a different group did the same experiment they found other results that it is the combinatorial cross fiber pathway theory. Sigh.