MCB Midterm 1 Material

Center-surround turns retinal ganglion cells into ____.

Center-surround turns retinal ganglion cells into edge detectors

Nearly all bodily systems are under both __ and __ control.

Nearly all bodily systems are under both sympathetic and parasympathetic control

Neurons that prefer the same eye are arranged in ____. Neurons situated along the vertical axis have very similar ____.

Neurons that prefer the same eye are arranged in columns. Neurons situated along the vertical axis have very similar ocular preferences

Bipolar cells come in two major flavors:

ON bipolar cells depolarize to light because they are inhibited by glutamate released from the cone (cones release less glutamate when hit by light) OFF bipolar cells hyperpolarize to light because they are activated by glutamate released from the cone (cones release less glutamate when hit by light)

V1 neurons are orientation selective:

ORIENTATION OF EDGE/BAR IS WHAT IT IS ENCODING. BAR MUST BE IN SAME ORIENTATION OF RECEPTIVE FIELD IN V1 NEURONS FOR V1 NEURONAL SPIKING. YOU DO NOT SEE THIS IN THALAMUS. IN THALAMUS IT IS CENTER SURROUND WHERE ANY ORIENTATION YOU MOVE BAR YOU DON:T GET A TUNING CURVE<. YOU GET A FLAT, SAME RESPONSE IN ALL ORIENTATION. ONLY CARE ABOUT ORIENTATION, NOT DIRECTION. DOESN'T HAVE TO MOVE IT JUST CAN FLASH ON AND OFF IN THIS ORIENTATION AND IT WILL GET SPIKES. Can get a tuning curve or neural response at different orientations.

OVERALL neuroscience methods can look at 1. 2. 3.

OVERALL neuroscience methods can look at 1. Single cell recording 2. Network level ( multi-cell recording) 3. Manipulation of neurons and circuits

What is the key responsibility of the ANS, and how does it accomplish this?

A key responsibility of the ANS is to maintain physiological systems within a specific operating range (blood pressure, body temperature, etc.). AKA HOMEOSTASIS. This is often accomplished by negative feedback as well as constant interplay between sympathetic and parasympathetic systems.

3. Ablations: to test inhibitory veto model.

3. Ablations: Immunotoxin ablation of SACs eliminates direction selectivity. Method: Wanted to test by killing specifically and only SACs. There was an Ab that would only bind to SACs so they coupled a toxin to that Ab and injected it. Tg is control picture, IT-tg is an injected animal. Can see green SACs disappear but works. Results: See how WT has directional preference (assymetric) but in the IT-tg it is now symmetric and doesn't fire in a preferrential matter. It seems inhibitory veto model is correct. Different complimentary approaches collectively give insight

Examples of systems under ANS control:

+Heart beat +Respiratory rate +Blood pressure +Pupil size +Release of sweat, tears, mucus and saliva +Thermoregulation (controlling body temperature) +Peristalsis (swallowing food) +Sexual functions

+Most cortical neurons prefer input to one eye over the other. This is called ____. +Largest fraction of cells are ____ that respond non selectively but a decent distribution throughout scale. +In monocularly deprived cat, you see a dramatic change in distribution of ocular dominance: Ex: close contralateral eye.

+Most cortical neurons prefer input to one eye over the other. This is called Ocular Dominance. +Largest fraction of cells are binocular that respond non selectively but a decent distribution throughout scale. +In monocularly deprived cat, you see a dramatic change in distribution of ocular dominance. Close contralateral eye you see that neurons almost all now prefer the open ipsilateral eye. Through development all neurons that would have preferred closed eye or both eyes shift preference to eye that is open OR become unresponsive. This says that experience drives wiring of the circuit in a fairly dramatic way. his suggests that the input from each eyes compete during development.

What are the two ways strabismus can be treated? What does the way strabismus is treated successful imply about the way information in our eyes is represented in the brain?

+Strabismus can be treated either with surgery or sometimes simply covering the healthy eye for several hours a day +This implies that there is active competition between the eyes for representation in the brain.

+Strabismus: +Children with strabismus appear to suppress the image from the _____. +In fact, you reflexively suppress a ____ even in adulthood (try pushing gently on one eye while either covering or uncovering the other eye). +Stabismus supports the fundamental idea that the way circuits wire in the cortex during our lifetime depend heavily on _______. +Can be corrected. But if not corrected by surgery (or covering healthy eye) you can have pronounced visual deficits like ____ but also other pronounced issues with vision. +Nothing wrong with _______, ___, and cortex. Information from the misaligned eye still gets _____ but doesn't arise to our level of consciousness. Shows that there is a ____ between information of our two eyes. Usually the combination of information from both eyes helps with depth perception (hence why they have deficits in this). But also if you get _____ information from both eyes you reflexively suppress the misaligned image from the misaligned eye.

+Strabismus: defect in musculature around the eye that causes misaligned eyes during early life that ultimately leads to pronounced visual defects, particularly in stereopsis (depth perception). +Children with strabismus appear to suppress the image from the misaligned eye. +In fact, you reflexively suppress a misaligned image even in adulthood (try pushing gently on one eye while either covering or uncovering the other eye). +Stabismus supports the fundamental idea that the way circuits wire in the cortex during our lifetime depend heavily on experience (especially early life). Strabismus: +Can be corrected. But if not corrected by surgery you can have pronounced visual deficits like stereopsis but also other pronounced issues with vision. +Nothing wrong with eyes, visual system, and cortex and it gets processed but doesn't arise to our level of consciousness. Shows that there is a competition between information of our two eyes. Usually the combination of information from both eyes helps with depth perception (hence why they have deficits in this). But also if you get incongruent information from both eyes you reflexively suppress the misaligned image from the misaligned eye.

+Your brain is NOT trying to reproduce the world (like a camera), but it's rather _____. Your brain is not trying to reproduce world as it is, it is trying to ____. +Your sensory systems don't care to find the most accurate information but the ___ and ____ to benefiting survival. +What's important are things that have ___ OR ____. +Your sensory systems try to find things _______ in ___ or ___ because they are filtering for ____ information. +Things that are ______ in the world are usually the most important and most ______ You sensory systems enhance the detection of _____ or _____ (spatial or temporal)

+Your brain is NOT trying to reproduce the world (like a camera), but it's rather trying to make sense of it. Your brain is not trying to reproduce world as it is, it is trying to process it. +Your sensory systems don't care to find the most accurate information but the most meaningful and relevant to benefiting survival. +What's important are things that have value OR consequences. +Your sensory systems try to find things dynamically changing in time or space because they are filtering for salient information. +Things that are changing in the world are usually the most important and most informative. You sensory systems enhance the detection of contrast or change (spatial or temporal)

3. Decision Making: 4. Motor Planning: 5. Motor Execution: _____ neurons connect optic lobes to motor neurons. Has a very large axon and wide diameter. ____ neuron is the cone that performs computation from retina to firing and encoding looming stimulus which activates the ____ which goes through the spinal cord equivalent of the fly and synapses on ___neurons.

3. Decision Making: COGNITIVE COMPONENT or "action selection". Decision fly has to make: what the fudge do I do? Fight? Flee? How to Flee? Jump! ex: Jumping straight at hand = bad direction. Decide to move to the correct direction. Many escape behaviors so it can make different kinds of jumps. Behavioral goal for the fly is to survive! 4. Motor Planning: Now that I know what tf I wanna do which motor movement do I need to execute the behavior? Neural code in neurons implements this decision. 5. Motor Execution: From neural activity to muscular response. "Giant Fiber" neurons connect optic lobes to motor neurons. Has a very large axon and wide diameter. VLP neuron is the cone that performs computation from retina to firing and encoding looming stimulus which activates the giant fiber which goes through the spinal cord equivalent of the fly and synapses on motor neurons.

Using Blood Pressure Control as an example, how does negative feedback help maintain homeostasis? 1. Blood pressure drops. 2. Baroreceptor neurons _____ their firing rate. 3. _____ in the medulla. HAVE TO HAVE ___ to get ___! 4. Activity of sympathetic neurons _____. 5. This drives an ____ in cardiac activity and ____of blood vessels. 6. Blood pressures ____. 7. This brings the baroreceptor neurons firing rate ______. 8. This system comes back into equilibrium.

1. Blood pressure drops. 2. Baroreceptor neurons decrease their firing rate. 3. A sign inversion takes place in the medulla. HAVE TO HAVE SIGN INVERSION TO GET NEGATIVE FEEDBACK! 4. Activity of sympathetic neurons increases. 5. This drives an increases in cardiac activity and constriction of blood vessels. 6. Blood pressures increases. 7. This brings the baroreceptor neurons firing rate back to the normal 'set point'. 8. This system comes back into equilibrium. Carotid sinus innervated by baroreceptor neurons of nodose ganglion. Innervates brain stem and carotid sinus. Baroreceptor neurons Increase firing rate when there is increased BP, and decrease firing rate when there is decreased BP. The caudal ventral lateral medulla is an inhibitory interneuron. As firing of excitatory baroreceptor increases, it activates the caudal ventral lateral medulla releases which releases inhibitory neurotransmitter, flipping sign of signal to -. Increase baroreceptor firing but in medulla you get inversion of sign where the firing rate of what the medulla synapses onto goes down. BP goes up, but firing rate decreases for neurons that synapse onto autonomic ganglia and effectors. Need to add inhibitory intenreuron with sign inversion so increase in BP translates to DECREASE in CO and PVR. LESS BP firing, less inhibition from medulla, more active red neuron so more autonomic response to increase CO and PVR.

What are four overall general methods to test models of ganglia direction selectivity?

1. Pharmacology 2. Recordings 3. Cell Ablations 4. Anatomy

1. Pharmacology: to test inhibitory veto model.

1. Pharmacology: GABA receptor blockade via Picrotoxin eliminates direction selectivity. CONTROL, moving in Null Direction: minimal firing. CONTROL, Preferred direction: firing. Picrotoxin, NULL DIRECTION: some firing. Picrotoxin, PREFERRED DIRECTION: some (more) firing. This doesn't prove the model to be correct but does not falsify it bc could GABAR be anywhere that impacted it not necessarily specifically from GABAR on ganglions. Shows GABAR is necessary but specific proposed inhibitory veto model not sufficiently proven yet.

Why use a digital code in the brain? List 3 advantages.

1. Propagate long distances: regenerates every node of ranvier. 2. Less susceptible to noise: subtracts out background noise. 3. More efficient: computational efficiency (easier to compute binary digital), takes up less space. Only most salient information processed and encoded. Analog will always be interrupted by background noise, but digital will subtract out that noise especially over long distance. Action potentials are both all or none and regenerate every nodes of ranvier. Computational efficiency— easier to compute at zeros and ones.

Five steps to neural circuit of escape in flies? The fly executes behavior (steps 1-5) in __-__ ms. Shows speed of the circuit - small animal huge axons.

1. Sensory detection 2. Computation on incoming object 3. Decision making 4. Motor planning 5. Motor execution The fly executes behavior (steps 1-5) in 20-30 ms. Shows speed of the circuit - small animal huge axons.

1. Sensory detection: +Visual response: +Tactile response:

1. Sensory detection: +Visual response: retina could detect increases or decreases in light. Photo-transduction via photo receptors that turn light photons in Action Potentials. +Tactile response: mechanosensitive hairs could detect air motion

2. Computation on incoming subject: +What is a computation? +What about with flies and escape behavior? +Anatomically, how is this computation achieved? +How does it differentiate a flash or light vs growing objects?

2. Computation on incoming subject: (through integration) +A computation is an encoding of critical feature about object that has relevant information to ultimately use for behavior. +The computation here is not just that there is an object (that is detection) but a key feature of objet that may be relevant to me—object expanding on retina most likely object coming at you at high velocity. +Two giant fiber neurons whose dendrites cover a vast amount of retina and can integrate a large amount of information from the physical world. Neuroanatomical underpinning of processing. These giant fiber neurons spatially summate and integrate large amount of information from the physical world. Neural anatomical substrate for spatial summation. +How does it differentiate a flash or light vs growing objects? A growing stimulus has a derivative in time.

2. Recording: to test inhibitory veto model.

2. Recording: Directly measuring temporal relationship of excitation and inhibition. Voltage Clamp to measure both excitatory and inhibitory currents. Downward CURRENT = excitatory, Upward CURRENT = inhibitory. RESULTS: Record current in ganglia when moving in PREFERRED DIRECTION: excitatory first, inhibitory second. Record current in ganglia when moving in NULL DIRECTION: powerful inhibitory first, excitatory second. NULL SIDE INHIBITION COMES NOT ONLY EARLIER BUT ALSO IS MUCH LARGER.

Basic anatomical plan of sensory systems: A to A (real energy to electrical) and then finally to spikes (A to D). Specialized cells for every modality performs either AA or AD conversion. Ex: mechano is analog force to digital spike ____. PNS has ganglion cells from the ____ lining spinal cord that send long neurons into entire body surface expressing mechanosensory receptors like __ on ____. These _____ then take force and generate receptor potentials which generates ____. Innervates the ____ of the spinal cord and that message gets sent synaptically to the ___and then relayed to the rest of the brain. ___, ___, and ___ all go through critical relay center: the thalamus. The exception is olfaction which bypasses the thalamus because it is ____. Sensory cell -> _____ -> thalamus -> cerebral cortex

Basic anatomical plan of sensory systems: A to A (real energy to electrical) and then finally to spikes (AD). Specialized cells for every modality performs either AA or AD conversion. Ex: mechano is analog force to digital spike directly. PNS has ganglion cells from DRG lining spinal cord that send long neurons into entire body surface expressing mechanosensory receptors like piezos on terminal afferents. These terminal afferent piezos then take force and generate receptor potentials which generates spikes. Innervates the dorsal horn of the spinal cord and that message gets sent synaptically to the thalamus and then related to the rest of the brain Somatosensation, vision, and audition all go through critical relay center: the thalamus. The exception is olfaction which bypasses the thalamus because it is evolutionarily older. Sensory cell -> spinal cord/brain stem -> thalamus -> cerebral cortex

Binocular neurons emerge in the ____. Different LGN layers synapse onto the _____. This is where information gets integrated. When LGN axons send axons into the ____ cortex, while neurons in each LGN layer are ____, neurons of diff layers of LGN project to the same ____ of the visual cortex!! Binocular region of visual cortex have ____ neurons that get information from _____! Very important for stereopsis (____ perception).

Binocular neurons emerge in the visual cortex. Different LGN layers synapse onto the same columns in the visual cortex. This is where information gets integrated. When LGN axons send axons into the ipsilateral cortex, while neurons in each LGN layer are monocular, neurons of diff layers of LGN project to the same COLUMNS of the visual cortex!! Binocular region of visual cortex have single neurons that get information from both eyes! Very important for stereopsis (depth perception).

Are there visual neurons that are binocular? If so, what experiment was conducted and what were the results?

Binocular neurons likely compute binocular disparity. EXPERIMENT: +Placed a bar in certain orientation and cover one eye or the other eye in correct orientation. Did this for Left Eye, Right Eye, and Both Eyes open (in both directions). Recorded spikes from neuron in Visual Cortex. RESULTS: +Found that this V1 neuron is driven by both eyes (don't need both to drive it but when stimulus present in both eyes you get a multiplicative effect where cell fires even more) so unlike the LGN and retina, neurons in the cortex CAN BE and frequently are BINOCULAR.

Basic architecture of autonomic circuits: What do post ganglionic neurons often release onto effectors? What are effector cells? Name 3 types:

Brain stem and spinal cord ⇨pre-ganglionic neurons (Cell bodies in brainstem/spinal cord, synapse onto ganglia) ⇨synapse onto ganglia ⇨ post ganglionic neurons (cell bodies on ganglia, synapse onto effectors) ⇨ effector cells. Post ganglionic neurons typically release adrenaline or acetylcholine onto effectors. Effector cells: non neural cells that will do something to actually change bodily system activity (ex: smooth muscle for peristalsis, glandular cells releasing sweat, cardiac muscles for heart) these are the tissues actually changing the systems. Not neurons themselves but receiving input from postganglionic neural cells.

CONCLUSIONS: Sensory Coding The brain attempts to generate a ______ representation of the world Sensory transduction performs _____ conversion. Digital codes are more _____ even when transmitted across long distances Higher cognitive areas synthesize information into _____.

CONCLUSIONS: Sensory Coding The brain attempts to generate a useful (but not necessarily accurate) representation of the world Sensory transduction performs analog to digital conversion. Digital codes are more immune to noise even when transmitted across long distances Higher cognitive areas synthesize information into useful perceptions

Cell bodies, dendrites, and local microcircuits are in ___ matter. Long-distance axon projections are in ___ matter. Clusters of neuron somata are called ___ or ___ (if laminated). Clusters of axons are called ___ (CNS) or ____(PNS).

Cell bodies, dendrites, and local microcircuits are in grey matter. Long-distance axon projections are in white matter. Clusters of neuron somata are called nuclei or cortex (if laminated). Clusters of axons are called tracts (CNS) or nerves (PNS).

Cerebral Cortex: central site of __, ___, and ___. · Massively expanded in humans, folded into your brain. __mm thick. __ layers. Has both __ and ___ matter. · Key structure in ____: everything you know about the world and experience is through this structure. · Specific Areas of function: look at patients with ______, you see damage in function that is specific. Arealization of function of the brain; ___ helps us see this and then we can also visualize it at the cellular level.

Cerebral Cortex: central site of cognition, preception, action. · Massively expanded in humans, folded into your brain. 2mm thick. 6 layers. Has both grey and white matter. · Key structure in perception: everything you know about the world and experience is through this structure. · Specific Areas of function: look at patients with focal ischemia and stroke, you see damage in function that is specific. Arealization of function of the brain; fMRI helps us see this and then we can also visualize it at the cellular level.

Color vision begins in the ________. Each cone subtype preferentially absorbs, and therefore detects, a different range of light wavelengths, according to which _____ it expresses. This is the basis for _____. Perceived color is computed _____.

Color vision begins in retinal cone photoreceptors. Each cone subtype preferentially absorbs, and therefore detects, a different range of light wavelengths, according to which opsin it expresses. This is the basis for color vision. Perceived color is computed downstream in the cortex.

Conclusions 1. LGN neurons relay retinal information about contrast and color to ___. 2. V1 has a precise _____ map of the visual world. 3. V1 neurons become _____ by integrating across center surround LGN neurons in a precise fashion. 4. Orientated neurons in V1 are arranged in ___.

Conclusions 1. LGN neurons relay retinal information about contrast and color to V1. 2. V1 has a precise retinotopic map of the visual world. 3. V1 neurons become orientation selective by integrating across center surround LGN neurons in a precise fashion. 4. Orientated neurons in V1 are arranged in columns.

Conclusions: 1. Rods and cones are the light sensitive neurons in the retina with complementary roles in vision. 2._______, via light absorption in the chromophore retinal, drives a signaling cascade that results in ____and ___ glutamate release. 3. Light depolarizes __ and hyperpolarizes ____ bipolar cells providing opponent channels for contrast detection. 4. RGCs exhibit _____ receptive fields that improve edge detection. 5. The retina can adapt to mean luminance over a huge range of light intensities in order to maintain sensitivity to ____ and improve perception

Conclusions: 1. Rods and cones are the light sensitive neurons in the retina with complementary roles in vision. 2. Rhodopsin, via light absorption in the chromophore retinal, drives a signaling cascade that results in hyperpolarization and reduced glutamate release. 3. Light depolarizes On and hyperpolarizes OFF bipolar cells providing opponent channels for contrast detection. 4. RGCs exhibit center-surround receptive fields that improve edge detection. 5. The retina can adapt to mean luminance over a huge range of light intensities in order to maintain sensitivity to local contrast and improve perception

Construction of a percept in the brain: Construction of percepts: very high level. Unbelievable ability to ____. There is extreme subtleties in an image, there are some changes or some ____ in the spatial domain that allows you to see local ____ like edges that allows you to bring out horses. Visual system analyzes scenes. +Nearly __/___ of your cortex is devoted to some aspect of visual processing.

Construction of a percept in the brain: Construction of percepts: very high level. Unbelievable ability to segment objects from the background. There is extreme subtleties in an image, there are some changes some derivatives in spatial domain that allows you to see local contrast like edges that allows you to bring out horses. Visual system analyzes scenes. +Nearly 1/3 of your cortex is devoted to some aspect of visual processing.

Cortex is organized in maps ____— physically a single neuron is a part of ____. These neurons have__,_____, and ____. Cortex has maps that are ____ so that each neuron is a member of ___.

Cortex is organized in maps on top of each other — physically a single neuron is a part of many maps at once. These neurons have receptor field location, another is orientation preference, and a third is the eye they prefer to (will talk about next class). Cortex has maps that are physically overlaying on each other so that each neuron is a member of multiple maps.

Different layers of the LGN also receive input from either the ___ or __ eye, not both

Different layers of the LGN also receive input from either the left or right eye, not both

In the visual system, why do first two neurons use analog and the it converts to digital in the third?

Digital is long distance. The retina is a very thin and highly organized layered structure with high density, and advantage of analog is no loss of information. So you have analong until you have ganlgion cells with long af axons that need digital.

What is the function of the Dorsal Root Ganglion? What is the function of the Ventral Horn? In what orientation do post-ganglionic cells lie relative to the spinal cord?

Dorsal Root Ganglion: incoming sensory information going to spinal cord Ventral Horn: synapse onto skeletal muscle for skeletal muscle control consciously. Huge system of unconscious control at the same time that broadly has same structure. Post-ganglionic cells lie vertically just outside spinal cord (dark yellow).

Downsides of digital encoding: (two reasons).

Downside of digital coding: 1. Losing Information: Many signals we want to encode are much higher than what neurons can fire. An AP is 1-2ms. Many signals we want to encode are much faster than neurons can fire. How can signals fluctuating more rapidly than neurons can fire with spikes be encoded? You lose something in the time domain. Anything faster than 1KHZ you're going to lose some information. Digital encoding at level of AP firing plays low pass level filtering. 2. FINITE SAMPLING RATE: Finite sampling rate (upper bound is action potential refractory period). Incoming sensory stimuli are a continuous signal defined at all times. So our neurons do sampling: neruons can't encode digitally at every time point so you sample at discrete time intervals and take snapshots. What is the value of this signal (ex: voltage) at time 1,2,3,4? You missed 1.5 and 2.3 etc. You're losing all this information, what you get is a red discrete time series (usually every 1-2ms). These differing values comes from differences in the number of action potentials per second. Absolute limit is the absolute refractory period of neurons 1-2ms but you have additional loss because you're trying to represent this analog continuous value as a discrete rate. You're losing a lot of information in time when turning it from a continuous valued function into something discrete (although this has advantages as discussed at other times).

During phototransduction, light _____ the photoreceptor membrane voltage. Light ->____ active ->____ channels closed -> hyperpolarized -> less ____ released.

During phototransduction, light hyperpolarizes photoreceptor membrane voltage. Light ->rhodopsin active -> Na+ channels closed -> hyperpolarized -> less glutamate released.

Some neurons in V1 are selective for binocular disparity. What experiment was conducted to test this, and what were the results?

EXPERIMENT: + Presented two different stimuli to each eye and presented these two bars at different binocular disparities to stimulate depth. Detected spikes for both L and R visual field bars at BD = 0, BD = 15, BD = 30, BD = 45, BD = 60. +Something with same location on retinas simulates object far away. Move that apart and increase binocular disparity and stimulate object moving closer to your face. RESULTS: They found that the neuron is tuned to a specific depth because it's spiking activity is tuned to binocular disparity. So this bar of light not only has to have the right location and orientation in space but also right distance from your head to drive this neuron (highest spiking at BD = 30). This neuron thus codes for binocular disparity or depth. +By extension if you have only one eye you have severe impairment in ability to process depth because these neurons are not activated very well. This is a fairly low level way of computing depth. Thus it is important not only to have two forward facing eyes but also that those eyes are far apart. More far apart = easier to perceive depth.

Far fro the fovea in your periphery, you have a low density of photoreceptors. This is because _________. The Rods are big because they respond to ______ (___,___) Smaller cones near the fovea are more dominant. Highest acuity in fovea because _______. However, there is much better ______ in periphery than fovea. This is because you have high density of rods. Lower acuity but much more sensitive to ____. Architecture of first layer already translates to aspects of our vision.

Far fro the fovea in your periphery, you have a low density of photoreceptors. This is because rods are bigger, they can't pack as densely as cones so less acuity vision. The Rods are big because they respond to low densities of light (twilight, starlight). Smaller cones near the fovea are more dominant. Highest acuity in fovea because since they are smaller they can pack more densely and provide better pixel resolution. However, there is much better photosensitivity in periphery than fovea. This is because you have high density of rods. Lower acuity but much more sensitive to lower levels of light. Architecture of first layer already translates to aspects of our vision.

What is the structure of retinal ganglion cells receptive fields?

Ganglion cells summate and differentiate. Receptive field of ganglion are locations in space that can modulate its firing rate. Receives input from a bunch of photoreceptors (most directly bipolar cells), defined by space that array of photoreceptors point to in the world. Receptive field of neuron is region of visual space that modulates ganglia firing rate up or down.

Hippocampus:

Hippocampus: site of short term memory formation, episodic and navigational memory.

Horizontal cells help generate an ______ by laterally ___________.

Horizontal cells help generate an inhibitory surround by laterally inhibiting release from cone terminals

Ocular dominance columns can be induced artificially. Explain the frog experiment and results that support this. We proved competition is necessary for binocular vision via monocular deprivation, but how can we prove it is sufficient in inducing OD columns?

How can we prove that competition is sufficient in inducing OD columns? Frogs do not have binocular vision— they have two eyes and the information of the two eyes never mix. Optic tectum is analogous to their cortex. One eye goes to opposite hemisphere so complete segregation in optic tectum, absolutely no competition. CONTROL: Use radioactive tracing then you only get contralateral labeling. EXPERIMENTAL GROUP: Transplanted an eye and it will grow and wire to one of the optic tectum. With tracer you see ocular columns!!! RESULTS: This demonstrates that species without competition, if you induce competition then you get ocular columns. Can generate pseudo-OD columns by adding input. Experience drives ocular dominance and how neural circuits are wired. COMPETITION IS SUFFICIENT IN PRODUCING OD COLUMNS!

Lateral Geniculate Nucleus neurons are ____. LGN on one side of brain takes information from ______ eye(s), and this information _______ is not integrated. This is because the LGN has ____ layers, and alternating layers respond to ____.

Lateral Geniculate Nucleus neurons are monocular. LGN on one side of brain takes information from both sides (left and right eyes), this information between the two eyes is not integrated. This is because the LGN has six layers, alternating layers respond to either the left or right eye (IPSILATERAL ROD: #2, IPSILATERAL CONES: #3 & #5. CONTRALATERAL ROD: #1, CONTRALATERAL CONES: #4 & #6)

Main points about the ANS: 1. The ANS promotes _____. 2. ______ is achieved through antagonistic actions between sympathetic (fight or flight) and parasympathetic (rest and digest) systems. 3. The main neurotransmitters released by ANS ganglion cells onto effector organs are ___ (parasympathetic) and ____ (sympathetic). 4. Transmitter action depends on ____. 5. ____ is a key mechanism for maintaining body system homeostasis.

Main points about the ANS: 1. The ANS promotes homeostasis. 2. Homeostasis is achieved through antagonistic actions between sympathetic (fight or flight) and parasympathetic (rest and digest) systems. 3. The main neurotransmitters released by ANS ganglion cells is acetylcholine (parasympathetic) and NE (sympathetic). 4. Transmitter action depends on the receptor. 5. Negative feedback is a key mechanism for maintaining body system homeostasis.

Methods for large scale investigation of neural networks: 1. 2. 3.

Methods for large scale investigation of neural networks: 1. Multi-electrode array recording: implant electrodes and measure neural activity and feedback to computer (can control multi-dimensional robotic arm for amputees to move objects). measure neural activity of brain over multiple neurons. 2. Two photon functional imaging: Mouse running under microscope and shows part of brain neurons flashing that sense Ca2+ when neurons fire. Indirect measure of activity .Ca2+ flux indicates active neurons. Can look at as many as 20k neurons in a single session. 3. Optogenetics: Precise control over neural activation or inhibition with light. Control individual groups of cells in this way

Methods for recording action potentials and synaptic inputs in single cells: 1. Extracellular Recording: Pros: Cons:

Methods for recording action potentials and synaptic inputs in single cells: 1. Extracellular Recording: +Measure APs with electrode 'close' to axon hillock. +Measure local field potentials. OBSERVATIONAL ONLY, does not perturb cells. + Insert wire into the brain in physical proximity to a neuronThis neuron will sometimes fire action potentials which can be picked up by the wire, is carried out by the wire (tiny signal in just microvolts) so we use amplifier to amplify the signal to a detectable level and record it. What does it do: measures APs, put it in audio amplifier, and can even hear the spikes. Pros: Relatively easy Minimally perturb recorded cell Mechanically stable (can be done in freely moving animals). Implant electrodes in animal and allow them to roam around behavioral arena. Cons: Only get APs, not synaptic potentials Often pick up multiple cells ( need to do computational analysis called spike sorting to differentiate). Cant manipulate cell's activity ~~~~~~~~~~~~~~~~~~~~~~ Because measuring on outside, you only get APs because you only can detect very large electrical disturbances. Intracellular changes are small and don't cause enough changes to be picked up by extracellular recording. Can't detect analog, only can detect digital aspects.

Methods for recording action potentials and synaptic inputs in single cells: 1. 2. 3.

Methods for recording action potentials and synaptic inputs in single cells: 1. Extracellular recording 2. Sharp intracellular 3. Whole cell patch clamp

Methods for recording action potentials and synaptic inputs in single cells: 2. Sharp Intracellular: Pros: Cons:

Methods for recording action potentials and synaptic inputs in single cells: 2. Sharp Intracellular: +Intracellular recording by impaling cell. +Uses very high resistance (small tip) electrode. Pros: Records BOTH spikes and synaptic potentials Don't dialyze cell with pipette solution Can control cell's activity (can inject current and see what happens when you make the cell spike!) Can see how analog potentials turn into digital APs. Cons: Cannot voltage clamp cell Not very mechanically stable (can't be in free moving animals) Prone to errors in measurements to high resistance of electrode ~~~~~~~~~~~~~~~~ Used in 40-80s.

Methods for recording action potentials and synaptic inputs in single cells: 2. Whole Cell Patch Clamp: Pros: Cons:

Methods for recording action potentials and synaptic inputs in single cells: 2. Whole Cell Patch Clamp: +Intracellular recording rupturing membrane. +Uses low resistance (large tip) electrode Pros: Records BOTH spikes and synaptic potentials. Can control cell's activity (voltage + current clamp). Can dialyze cell with exogenous factors Can voltage clamp reasonably well. Mechanically stable. Cons: Dialyzes cell with pipette solution (lose internal factors over time). Dies eventually. ~~~~~~~~~~~~~~~~~~~~~ Introduced in late 70s Intracellular recording technique but instead of impaling the cell you literally attach the lectrode mch alrger to the cell surface and rupture the membrane via suctio nand it ceals onto the glass pipette so electdode is electrically conttinous with neuron. Incredibly high signal to noise measurement and allows you to control cells activity and voltage very well. Primarily used to look at subtrheshold response but also get the spikes. You can control cell actibity, stop it from spiking, can inject chemicals, dyes to trace neurons, 2ndary messengers, etc. Can do a lot of molecular exchange and manipulations. can look at synaptic conductanes with voltage clamps and can even behaving (even freely behaving) organisms Con: The pipette has volume a million times larger than cell and you rapidly equilibrate with the pipette with the solution in the pipette so all good stuff in cell like enzymes spill out of the cell and the cell eventually dies

Molecular Transduction occurs in specified sensory cells types: Specialized cells 'transduce' the stimulus and perform _____ themselves or one-three cells downstream. Photoreceptors in visual system ____ spike, hyperpolarization in voltage (___) to bipolar (_____) and then finally ganglion cell which converts it into _______.

Molecular Transduction occurs in specified sensory cells types: Specialized cells 'transduce' the stimulus and perform A/D conversion themselves or one-three cells downstream. Photoreceptors in visual system do not spike, hyperpolarization in voltage (analog) to bipolar (analog) and then finally ganglion cell which converts it into spikes/action potentials/digital.

The Hubel and Wiesel model for the genera6on of orientation selectivity

Multiple on center off surround LGN neurons along one another in axis will synapse onto the same cell in the V1 that will integrate this information and have an orientation preference (oblong elipse).

Orientation selectivity is constant along the ___ axis of the cortex. This is called an ___ column--this is a column where all neurons have the same preferred ___ and these same neurons can have a preferred ___ location. Have columns of 250-500 neurons that encode same orientation AND visual receptive field location. Cortex is organizing maps on top of each other. Physically a single neuron is part of many maps at once. They thirdly have an ____ preference too. Every neuron is a member of multiple maps.

Orientation selectivity is constant along the vertical axis of the cortex. This is called an orientation column--this is a column where all neurons have the same preferred orientation and same preferred receptive field location. Have columns of 250-500 neurons that encode same orientation AND visual receptive field location. Cortex is organizing maps on top of each other. Physically a single neuron is part of many maps at once. They thirdly have an eye preference too. Every neuron is a member of multiple maps.

Why have parallel ON and OFF pathways in the retina?

Parallel ON and OFF channels in the retina generate downstream ganglion neurons that can respond to either increases or decreases in light. You have photoreceptors that act as pixels and ganglion cells integrate information from almost always more than one photoreceptor. How do you get computation across space? contrast? compare things in space and time. Ganglion cells compare things in space in time, way they do in space is summing input from all photoreceptors that converge on them via bipolar cells. Locations in cells that can modulate that cells firing rate. Input from bunch of photoreceptors so it is defined by the space that those photoreceptors point at in the world. What defines region of space and visual field is defined by which photoreceptors pass information to the ganglion cell eventually. Receptor field of neuron is the visual and retinal space, the region of visual space, that will modulate the neuron's firing up or down.

How does vasodilation via parasympathetic activity occur, and what is the story of the drug Sildenafil in this? Briefly also include how sympathetic activity increases BP.

Parasympathetic activity ⇨ Acetylcoline ⇨ Nitric Oxide (NO) ⇨ cGMP ⇨relaxatio nof muscles arund arteries ⇨Vasodilation ⇨ decreased blood pressure PDE inhibits cGMP and thus inhibits vasodilation. Thus, PDE inhibitors increase cGMP and cause vasodilation. However, Sildenafil only inhibits PDE specifically in the sexual organs. Sympathetic activity ⇨ Epinephrine ⇨ ⇨ ⇨vasoconstriction ⇨ increased blood pressure

How can you test the following hypothesis for both necessity AND sufficiency? Hypothesis: Giant fiber neurons integrate "looming" output information in the retina, activate, and drive fast escape jumps.

Patch them (Electrophysiology). Put electrode in one of these cells and see what this neuron fires to. What kind of stimuli makes this neuron fire? It is looming stimuli, growing stimuli? Let's say it fires to looming stimuli. Now how do we prove necessity and sufficiency? NECESSITY: Test by severing the nerve or temporal blocking, proves necessity. SUFFICIENCY: Test to see if even in absence of stimulus if you stimulate a giant fiber neuron the fly will escape. You can do this with optogenetics. Put channelrhodpsin in giant fiber neuron and flash a light to get it to activate. Artificial optogenetic activation of the giant fiber neurons specifically drives fast escape jumps.

Perception is an _____, but it is not itself a reality. Illusions tell us this! Perception is a result of integrating our ______ with stimuli input. Looking for structures that make sense. The computation and encoding does not occur in retina for shape perception. While there is directional and orientation selectivity in the retina, things higher level such as_____ and _____ perspectives occur in the cortex.

Perception is an inference about reality, but it is not itself a reality. Illusions tell us this! Perception is a result of integrating our world experience with stimuli input. Looking for structures that make sense. The computation and encoding does not occur in retina for shape perception. While there is directional and orientation selectivity in the retina, things higher level such as large overall patterns and wholistic perspectives occur in the cortex.

Photoreceptors and bipolar cells are ____ until you get to ganglion cells (3rd neuron) that converts it to ___. In skin it's the first neuron that directly turns it into ____. Olfactory and auditory is in the ____.

Photoreceptors and bipolar cells are analog until you get to ganglion cells (3rd neuron) that converts it to digital. In skin it's the first neuron that directly turns it into spikes. Olfactory and auditory is in the first ones too.

The pons are a part of the brainstem. What do they do?

Pons: contain nuclei that relay signals from the forebrain to the cerebellum, along with nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture.

Why have two eyes and why have them aligned in the first place? Why do predators have forward facing eyes and preys side facing eyes?

Predators tend to have forward facing eyes. Anything at center of our gaze gets information from both eyes (both retinas), and we call this the binocular region of visual space. Other regions are called monocular regions. Prey needs wider field of vision to see where predators may be and predators want to focus on what they are hunting.

The spatial map is broken up into groups of columns with different orientation preferences. Why put these neurons next to each other?

Put neurons doing same thing next to each other so amount of wiring between neurons can be minimized. Don't have to spread information far, efficient in space.

RGCs code two things:

RGCs code two things: increase in luminence in center but also when it turns off. Signaling both increases and decreases of luminence both in time and space

RGCs shift their sensitivity depending on the average ____.

RGCs shift their sensitivity depending on the average background intensity. RGCs preserve their dynamic range by shifting their sensitivity.

Retinotopic Map: Anesthetized animal and kept its eye open looking at this image for 17 hrs. _____ stains active neurons so they injected this and saw remarkable correspondence with ___ and ___.

Retinotopic Map: precise spacial map of the visual world in the visual cortex. The retina is spatially represented onto the cortex. Anesthetized animal and kept its eye open looking at this image for 17 hrs. Cytochrome oxidase stains active neurons so they injected this and saw remarkable correspondence with stimulus on screen and active neurons in the cortex.

There are two classes of photoreceptors: rods and cones

Rods: very light sensitive, larger, concentrated in peripheral retina Cones: less light sensitive, smaller, concentrated in the fovea, responsible for color vision

Object Segmentation-- what is it and where does it occur?

Segregation objects occurs in the visual cortex. Many objects overlapping, tesselated, or close to each other— visual cortex segregates these objects.

What is sensory transduction, and what are its 3 stages?

Sensory Transduction: the process of transforming external stimuli into neural activity Three stages of sensory transduction: 1. Molecular transduction: (transform energy or chemicals into a voltage change). The process by which specific receptor proteins on primary sensory cells convert energy or chemicals into voltage changes (also known as potentials or receptor potentials). These voltage fluctuations over time represent that outside stimulus. 2. Sensory coding: (conversion into a digital code of action potentials). Takes the initial electrical change that is meant to be a representation of the physical stimulus, and turn this electrical analog signal into a digital code of APs. Digital codes are a binary code in time that is representative of a non-binary code, an analog for example of changes in sound pressure. 3. Construction of a percept: (e.g., in the cerebral cortex). High level representation in your brain that tells you what an object is, it's meaning, where it is, etc. Integration and perception of sensory coding highly influenced by your inferences forms percepts.

What sort of conversion does sensory encoding conduct? How are intensity values transformed in this conversion?

Sensory encoding: analog to digital conversion Go from continuously defined time series wave form into a discrete representation— go from continuous representation where voltage is defined at all time points to digital binary all or none action potentials. Continuous waveform not transmitted to brain, what is transmitted to brain is APs. Tension on phospholipid membrane elicits an ionic flux. receptor potential is change in voltage over time. Go from continuous wave form (voltage defined at all time points) to something digital, binary, discrete representation, all or none: action potentials The way to transform an intensity value you increase the frequency of action potentials (more action potentials per unit time). You get more AP per unit time when transforming intensity codes. If you want to represent a continuous time varying signal you have to turn it into more AP per unit time. Larger depolarization, large receptor potential, more AP per unit time.

Some retinal ganglion cells are direction selective. Motion detection requires ____ Without ______, you get the same response from all directions. ____ don't exhibit any form of asymmetry, they are like pixels. So we know that the direction selectivity does not come from the ____ themselves but more downstream in the circuit (in the ganglia).

Some retinal ganglion cells are direction selective. Motion detection requires asymmetry. Without asymmetry you get same response from all directions. Photoreceptors don't exhibit any form of asymmetry, they are like pixels. So we know that the direction selectivity does not come from the photoreceptors themselves but more downstream in the circuit (in the ganglia).

What neuron is the source of directional inhibition on RGCs? How was this seen? Where is the asymmetry in amacrine to RGC circuits? What testing shows this?

Starburst Amacrine Cells (SACs) cover entire retina and synapse onto direction selective ganglia. These SACs are primary GABAergic neurons that synapse onto ganglion cells. Can see this by inducing SACs to depolarize and release GABA and see and record its effects on the ganglia. They don't fire action potentials, and their dendrites act independently to release GABA. Amacrine cells on the null side of the RGC make stronger inhibitory synapses. Direct pair recordings show that from null side you get a lot more inhibition than the preferred side. Both stronger AND delayed inhibition depending on the side you come from. SACs on all sides, can get inhibition from any direction but you get stronger inhibition on the null side. What generates preferred direction is you get more inhibition on one side of the ganglion cell than on other. Preferred side excitation before inhibition bc weaker synapses. Null side you get stronger inhibition first bc stimuli coming from that direction.

What was Otto Loewi's Experiment trying to determine? How did he determine the results, and what do the results mean?

Stimulated Vagus nerve in donor heart, noticed heart rate slowed. Collected fluid sample from the stimulated Vagus nerve. Applied fluid to recipient heart that had no innervations, and heart rate slowed. This proved that it is a chemical, not electrical signal, that stimulates heart rate slowing. This chemical is acetylcholine.

What are sensory stimuli? What do sensory systems do with sensory stimuli?

Stimuli are forms of energy (light, sound, force) or chemicals (odors and tastes) Sensory systems take energy and turn it into something abstract— neural activity.

What is the difference in ocular dominance columns in individuals with strabismus vs normal? What experiment was conducted and what were the results to test this?

Surgically induced strabismus sharpens ocular dominance columns. Experiment: Induced strabismus in one cat. Inserted tracer to visualize ocular dominance columns. Counted # of cells that are binocular, contralateral, and ispilateral. RESULTS: Found that instead of bell curve distribution of binocular/contralateral/ipsilateral preference, there were almost no binocular cells. Primarily contralateral and ipsilateral In strabismus, you have both eyes functioning but losing competition bc not overlapping, different since misaligned eyes are looking at different angles. Columns look sharper and better defined with the misaligned eyes. Black and white zones with greyish areas in regular but not in the misaligned eyes. Eyes in misaligned aren't competing so get their own territories. This implies that visual defects in children with strabismus is due to ocular dominance columns that are too sharp

Synapses onto Ganglia neurons (sympathetic and parasympathetic) almost always release ____that act on fast ____ receptors to activate ____. Synapses onto Effectors use ____, ___, or other transmitters (depends on system). Synaptic actions of autonomic circuits operate on ______: milliseconds, seconds, minutes.

Synapses onto Ganglia neurons (sympathetic and parasympathetic) almost always release acetylcholine that act on fast nicotinic Ach receptors to activate postganglionic neurons Synapses onto Effectors use acetylcholine, NE, or other transmitters (depends on system). Synaptic actions of autonomic circuits operate on multiple timescales: milliseconds, seconds, minutes.

What is the synaptic mechanism of ocular dominance plasticity?

Synaptic mechanisms are fundamental to wiring of neural circuits throughout the brain. Hebbian Model: +LTD: non-active synapses are actively weakened. +LTP: active synapses are strengthened. Non-Hebbian Homeostatic Model: +Homeostatic plasticity: The idea that neurons scale up or scale down their synaptic inputs to maintain a stable level of activity +Since closing one eye reduces net synaptic drive to binocular neurons, active synapses scale up their strength to maintain total drive of cell. +Neuron receiving binocular input. Close one eye, it spikes less and loses a lot of input. Because it is spiking less than optimal range, the neuron scales up synaptic input so it gains back normal firing. Because you can't scale up the inputs from the closed eye, it is the active inputs that get stronger or more numerous. So net effect is neuron only responds to eye that remains active and returns to normal firing rate (within optimal homeostatic range) but only responsive to open eye.

The complete circuit diagram from sensation to autonomic action (via emotional systems)

Take sensory system information and ultimately funnel it into the effector cells. Limbic system generates fear response which engages sympathetic nervous system⇨ hypothalamus and brain stem ⇨ spinal cord and autonomic ganglia (somatic motor nerve, autonomic nerve, pituitary) ⇨effector cells (skeletal muscles, smooth/cardiac muscle, endocrine gland) ⇨emotional responses/behaviors (freezing/fighting, rise in BP, stress hormone release).

Function of Thalamus?

Thalamus: primary function is as a relay center through which sensory nerves transmit signals from the spinal cord and brainstem on the way to the cerebral cortex. Small structure, so huge bottle neck of info going into thalamus.

The Lateral Geniculate Nucleus (LGN) has ___ layers. The left and right eyes both synapse on the ___ and __ LGN but go to different layers. Information is still ____. The LGN is largely a 'relay center'. There is no ____ of information. Cortex almost exclusively gets info from thalamus. General processing allows it to not get to the cortex during sleep. Could have selective attention by inhibiting parts of the thalamus and enhancing others. Thalamus is good for a ______ relay, not just obligatory Put an electrode into the brain and present stimuli to retina you can measure the level of response in the LGN and map the receptive field. _______ receptive field essentially identical to retina. Why even have this structure? Information is largely preserved, not trying to change or transform information. This this is just a relay center. You simply want to relay it downstream.

The Lateral Geniculate Nucleus (LGN) has 6 layers. The left and right eyes both synapse on the L and R LGN but go to different layers. Information is still segregated. The LGN is largely a 'relay center'. There is no transformation of information. Cortex almost exclusively gets info from thalamus. General processing allows it to not get to the cortex during sleep. Could have selective attention by inhibiting parts of the thalamus and enhancing others. Thalamus is good for a CONTROLLED relay, not just obligatory Put an electrode into the brain and present stimuli to retina you can measure the level of response in the LGN and map the receptive field. Center-surround receptive field essentially identical to retina. Why even have this structure? Information is largely preserved, not trying to change or transform information. This this is just a relay center. You simply want to relay it downstream.

The Primary Visual Cortex (V1 or Striate Cortex):

The Primary Visual Cortex (V1 or Striate Cortex): is where information is transformed and integrated between eyes. Information transformed radically from thalamus to visual cortex.

Autonomic Nervous System (ANS):

The autonomic nervous system is the subdivision of the peripheral nervous system that regulates body activities that are [generally] not under conscious control. It's really a collection of modulatory systems that change how your body reacts to it's environment without requiring conscious control. It's primary function is to maintain bodily systems within specific operating range, to maintain and promote homeostasis!

The center of your visual field (from the fovea) is highly magnified in V1:

The center of your visual field (from the fovea) is highly magnified in V1: Large receptive field (periphery) lower acquity. Smaller receptive field = higher acuity = greater cortical magnification/more portion of visual cortex dedicated to processing. Massive overrepresentation (many more neurons processing central view, fovea representation). High density of photoreceptors in fovea so to process that info you need more cortical neurons. Not having more cortical neurons for fovea portion would make fovea concentration of photoreceptors irrelevant bc not enough to process it. Hencce there are more cortical neurons representing the fovea so that you can get high visuospatial acuity. Overrepresentation of high acuity regions (applies also to mechano and other somatosensory modalities). Take high acuity region of cortex and move it around. Every 3-4 seconds eye moves around to move high acuity region around and look around.

The ___ and ___ focus light onto the retina. The ___ acts as an aperture adjusting light levels

The cornea and lens focus light onto the retina. The pupil acts as an aperture adjusting light levels

The density of photoreceptors sets determines ______ The density of retinal photoreceptors sets _____ of spatial acuity. The density of the photoreceptor cells is highest in the ____. You have about ____ photoreceptors in your eye.

The density of photoreceptors determines visual acuity. The density of retinal photoreceptors sets upper bound of spatial acuity. The density of the photoreceptor cells is highest in the fovea. You have about 100 million photoreceptors in your eye.

The eye closing does not alter receptive fields in ___ or ___, so changes must be taking place in the ___.

The eye closing does not alter receptive fields in retina or LGN, so changes must be taking place in the cortex

The heart is innervated by two main nerves. What are they, and what chemicals released by them increase or decrease heart rate?

The heart is innervated by two main nerves: 1.The parasympathetic (or Vagus) nerve decreases rate via acetylcholine. 2. The sympathetic nerve increases heart rate via norepinephrine. (although downstream effect of increasing/decreasing heart rate really depends on the receptor type, not the NT itself)

How does binocularity give you depth perception?

The relative distance to an object determines the binocular disparity. Binocular Disparity: difference between the relative angles that the object falls on two retinas. So by computing binocular disparity the relative distance can be estimated. Very far away (Ex: at infinity) = binocular disparity is zero (projects onto same location of retinas for both eyes). Closer = binocular disparity increases (projects at different spots on the two retinas. Ex: one is +50 other -50.) Neurons use information to compute based on binocular disparity the relative distance of the object. Need information from both eyes into single binocular neuron. This is likely fundamental basis of stereopsis.

The retina has three major layers:

The retina has three major layers: photoreceptors, bipolar cells, and retinal ganglion cells

Types of retinal ganglion cells: (7)

Types of retinal ganglion cells: 1. Very low contrast 2. Color contrast 3. Large stimuli 4. Moving stimuli 5. Looming stimuli 6. Global motion 7. Intrinsically photosenstive

How can you visualize ocular dominance columns in the V1? What about its functionality?

Visualize: Inject trans-neuronal tracer into one of the eyes. One such tracer is a radioactive proline amino acid that gets transported transynaptically from eye to thalamus and thalamus to cortex. Can visualize the projection zones of L eye going to R eye and you get visualization of ocular dominance columns. One eye was injected and other was not. Functionality: Measure neuron preference via electrophysiology and build statistical distribution of ocular dominance preference. Put electrode (electrophysiology) in cortex and see columns share same receptive field, orientation preference, and share the same ocular dominance. Reinforces notion that functionality of visual cortex is organized in columns— orientation and OD columns.

What are the two hypothetical circuits for motion detection?

What are the two hypothetical circuits for motion detection? 1. Cross-Correlation Model (Insects). ->Motion detection using a delay line. 2. Inhibitory "Veto" Model (humans & mammals). ->Motion detection using inhibition and a delay line

What happens to Ocular Dominance if you close both eyes? What hypothesis does this support and what two things drive it?

While it wouldn't change the distribution of ocular dominance between the two eyes, total visual deprivation decreases the number of cortical neurons that respond to visual stimulation. You now have a large # of neurons that no longer respond or are no longer orientation tuned. Most neurons lose encoding orientation or stop encoding. Supports competition hypothesis. Shows two factors impacting Ocular Dominance: 1. Need activity to keep circuit functional. 2. You have competition between two eyes during development to get responsive neurons for them.

Whole cell patch clamp recording 'modes' Voltage clamp (VClamp): 1. Prevent voltage activated ____. 2. Measure ___ plots 3. Separate conductances with different ____. "Current clamp" (Iclamp): 1. Measure ____. 2. Inject __ (positive or negative) 3. Can measure ___ plots (but cannot isolate conductances).

Whole cell patch clamp recording 'modes' Voltage clamp (VClamp): 1. Prevent voltage activated conductances 2. Measure I-V plots 3. Separate conductances with different reversal potentials "Current clamp" (Iclamp): 1. Measure membrane potential 2. Inject current (positive or negative) 3. Can measure V-I plots (but cannot isolate conductances)

saccade

is a quick, simultaneous movement of both eyes between two or more phases of fixation in the same direction.

What is the retinogeniculate pathway?

optic tract -> Thalamus LGN -> optic radiation -> visual cortex.

Define Behavior. Why is a brain needed for a behavior if singe celled organisms like amoeba still exhibit behavior? Site two reasons. Major function of our nervous system is to coordinate our ____ and change ___ to promote survival.

· Behavior: motor action in response to an eternal cue. · Humans vs amoeba—amoeba is a single celled organism and we are multi-cellular. 1. We need a nervous system because we need organization of cells within a multi-cellular organism to execute processes. 2. We can learn and achieve behavioral plasticity. This requires neural system plasticity. Learning in single cell organisms is largely limited relative to humans. We are extremely adaptive and our behavior can change so we can optimize our survival and reproduction. Major function of our nervous system is to coordinate our large body and change behavior to promote survival.

Primary function of the Autonomic Nervous System: Example:

• The ANS promotes homeostasis - It maintains bodily systems within a specific operating range. Example: During vigorous exercise even though your heart beat speeds up several times, you blood pressure and temperature increase only slightly. • Allows you body to rapidly adapt to behavioral conditions: + Increased blood flow and oxygenation to muscles during vigorous activity + Increased blood flow to G.I. systems during rest and digestion

What are the three major subdivisions of the Autonomic Nervous System?

• The sympathetic nervous system: +Fight or Flight +ADRENALINE!!! • The parasympathetic nervous system: +Rest and digest +Acetylcholine • The enteric nervous system: +Control of the GI (gastrointestinal) system +Acetylcholine.