Phgy 314
cerebral ganglion in aplysia
"brain"
buccal ganglion in aplysia
"mouth"
clinical tests that can be done for peripheral hearing disorders
- audiometry, which tests with pure tones - bone conduction (Rinne test) - otoacoustic emissions
resting-state networks at the macro-scale
- based on slow-fluctuations in the BOLD signal that in their larger part reflect fluctuations in neurophysiological activity - can be defined according to similarity of time-courses of slow-fluctuations in the EEG, MEG, and NIRS optical imaging techniques
characteristics of chronic neuropathic pain
- chronic debilitating disease that affects 1 / 5 individuals - associated with mechanical allodynia and spontaneous pain - 50% of patients obtain partial relief
primary auditory cortex characteristics
- tonotopic map in kHz - info is organized in columns - extensive crossing of pathways - neurons can have receptive fields for locations in space - flanked by up to 9 other areas, many with tonotopic organization
human hearing range in decibels
0 - 120 dB
significance of the origin of a power spectrum
0 frequency
range of audible amplitude
0.002 - 2000 dynes / cm^2
What is the scale of cortical layers?
0.4 - 0.6mm
Which layers of the LGN contain magnocellular cells?
1 and 2
What is the scale of molecules?
1 angstrom
What is the scale of synapses?
1 micrometer
3 inputs to CA3 in rats
1. 50-80 mossy fibres from DG 2. 3,500 perforant path synapses from EC II 3. 12,000 recurrent collaterals from other CA3 cells, with 8,000 of them going to basilar dendrites in the stratum oriens and 4,000 of them going to apical dendrites in the stratum radiatum
3 general roles for the extrastriate visual areas
1. More directly involved than V1 I guiding visual perception and behaviour 2. Useful for measuring quantities that can't be measured with small receptive fields 3. Interact more than V1 with the animal's cognitive state
4 types of touch receptors
1. Pacinian corpuscles 2. Meissner's corpuscles 3. Merkel's discs 4. Ruffini's endings
What are 3 pieces of evidence for the cochlear amplifier?
1. The tuning and sensitivity of the cochlea is greater than predicted by its passive mechanical properties. 2. Tuning is sharpest at low amplitudes, showing that there is an active means of amplification. 3. There are evoked and spontaneous otoacoustic emissions.
central auditory pathway
1. afferents 2. cochlear nucleus 3. superior olivary nucleus 4. inferior colliculus 5. medial geniculate nucleus 6. auditory cortex
What are 3 uses for studying spontaneous activity and resting-state networks?
1. analyzing the pattern of connections between areas in the healthy human brain 2. for diagnosing neurological and psychiatric conditions 3. for serving as bio-markers for progression of diseases and testing for efficacy of drugs
The hypothalamus controls which 3 systems to maintain homeostasis?
1. autonomic nervous system 2. motivational system 3. endocrine system
What are 4 things that happen with a stress response?
1. avoidance behaviour 2. increased vigilance and arousal 3. activation of the sympathetic division of the ANS 4. release of cortisol
4 main components of the dorsal horn
1. axon terminals of periphery sensory neurons 2. cell bodies of interneurons and their axon terminals 3. projection neurons' cell bodies (axons sent up to the brainstem) 4. descending modulation (cell bodies in the brainstem send axons that terminate in the spinal cord to modulate pain inputs)
What are 6 things that the hypothalamus regulates to maintain homeostasis?
1. blood pressure and electrolyte balance 2. circadian rhythms 3. body temperature 4. energy metabolism 5. reproduction 6. emergency response to stress
What are the 3 physiological parameters that influence BOLD signal?
1. cerebral blood volume 2. cerebral blood flow 3. oxygen consumption
mouse osteoarthritis experiment with injured animal 3 hypotheses of what caused pain
1. closer to AP threshold (more depolarized) already due to the downregulation of hyperpolarizing potassium channels - with this method, it was found that a stimulus that shouldn't hurt didn't, but one that should hurt more (hyperalgesia) 2. up regulation of sodium channels so that the AP threshold comes down - with this method, a light stimulus didn't cause pain cause the properties of mechano-sensitive channels haven't changes, but hyperalgesia is present 3. reduce activation threshold of mechano-sensitive channels at the nociceptor level by changing the properties of mechano-sensitive channels - with this method, a light stimulus causes an AP, which causes pain (allodynia) and there is also hyperalgesia
3 mood disorders
1. depression 2. bipolar disorder 3. anxiety disorder
What are the 2 strategies for sound localization in the horizontal (azimuth) plane?
1. difference in arrival time 2. intensity difference
4 spatial cell types in the MEC
1. grid cell 2. head direction cell 3. conjunctive cell 4. boundary vector cell
4 outcomes for the measurement of a stimulus
1. hit (correctly identify stimulus above criterion)) 2. miss (identify stimulus below criterion) 3. false alarm (identify stimulus above criterion) 4. correct rejection (reject stimulus below criterion)
What are 3 types of information that auditory afferents encode?
1. info about which nerve fibre is activated 2. the rate of spiking 3. the temporal pattern of spiking
What are 4 hypotheses of the functional role of spontaneous activity and resting state networks?
1. involvement in functionally relevant info processing 2. non-random, coordinated interaction of ongoing and evoked activity in perception and behaviour 3. scanning of context possibilities, making it easier to lock on a concurrent "scene" or stimulus 4. maintenance and enforcement of synapses as part of transforming short term to long term memory
What are the 3 types of sensory neurons?
1. mechanoreceptors 2. proprioceptors 3. nociceptors
list of 10 resting state networks that exist
1. medial visual 2. occipital pole visual 3. lateral visual 4. default mode network 5. cerebellum 6. sensory-motor 7. auditory 8. executive control 9. fronto-parietal perception-somethesis-pain 10. front-parietal language-cognition
What are the four types of information conveyed by all sensory systems that yield sensation?
1. modality 2. location 3. intensity 4. timing
pain transduction pathway
1. nociceptor has a peripheral ending, where there are mechxnosensitive ion channels that convert mechanical stimulus to an electrical signal 2. axon with AP runs to a cell body close to the spinal cord 3. The central terminal goes into the spinal cord and synapses on interneurons 4. a projection neuron send a pain signal up to the brain
3 parts of the central executive
1. phonological loop 2. episodic buffer 3. visuospatial sketch pad
3 main steps of coding sensory information
1. physical stimulus 2. set of events transforming the stimulus into nerve impulses 3. a response to this signal in the form of a perception or conscious experience of sensation
4 types of implicit memory
1. priming 2. procedural 3. associative learning - emotional responses and skeletal musculature 4. non associative learning
What are 4 reasons that working memory is important?
1. reasoning 2. comprehension 3. learning 4. memory updating
3 reasons for decreased inhibition at the level of the dorsal horn
1. reduced strength of synaptic inhibition 2. conversion from postsynaptic inhibition to excitation 3. opening of polysynaptic excitatory pathways from deep to superficial spinal dorsal horn (AB fibre input isn't blocked)
mechanism of receptor cell activation
1. stapes pushes on oval window and produces pressure wave in scala vestibuli 2. pressure wave is transmitted to the basilar membrane 3. round window acts as a pressure release
structure of CA1 (layers inside-out)
1. stratum lacunosum-moleculare that receives entorhinal afferents from LEC and MEC 2. stratum radiatum, where CA3 inputs come in through Schaegger collaterals and inputs come from commissural fibres 3. stratum pyramidale, where pyramidal cells are 4. stratum oriens, where basal dendrites are
structure of CA3 (layers inside-out)
1. stratum radiatum that contains entorhinal afferents and mossy fibres from the dentate gyrus, make synapses in the stratum lucidum 2. stratum lucidum that receives inputs of the most proximal part of apical dendrites that are very thorny 3. stratum pyramidale, where pyramidal cells live 4. stratum oriens, where basal dendrites sit, forming recurrent collaterals
What are the 3 divisions of the ANS?
1. sympathetic 2. parasympathetic 3. enteric
How many cells of each type in the rat dentate gyrus?
1.2 million densely packed granule cells, 4 thousand basket cells, and 32 thousand hilar interneurons
What is the scale of neurons?
10 - 100 micrometers
What is the intensity difference between ears for interaural level difference sound localization at 10,000Hz?
100:1
How much is basilar movement amplified for low amplitude stimuli?
100x
What is the scale of large scale neural networks?
10cm
How many stereocilia on each hair cell?
10s - 100s
What is the density of neurons in the cerebral cortex?
12 x 10^4 / mm^3
Around what day of embryogenesis do sensory neurons finally differentiate into their final types?
14
hair cells numbers
16,000 per ear, 3,500 of which are inner hair cells and 12,000 of which are outer hair cells
What is the scale of the CNS?
1m
What is the scale of cortical columns?
1mm
When in the development of humans does the perception of word meaning mature?
2 - 4 years
How large is a conventional fMRI voxel?
2 x 2 x 2 mm
Human hearing range by age 20
20 - 16,000Hz
Newborn human hearing range
20 - 20,000Hz
human hearing range by retirement age
20 - 8,000Hz
A 10 fold increase in pressure corresponds to how many decibels?
20 dB
What happens to pyramidal cells during sharp-wave ripples?
20-25% of hippocampal pyramidal cells are activated, but are silent during theta oscillations
ratio of rods to cones
20:1
What frequencies are audible to humans?
20Hz to 20,000Hz
What is the total amplification of sound pressure in the middle ear?
22x
What is the intensity difference for interaural level difference sound localization at 1,000Hz?
2:1
The cochlea contains how many fluid-filled compartments and what are they?
3 - scala vestibuli, scala media, and scala tympani
hippocampal gamma oscillations
30 - 100Hz oscillation in local field potential in the hippocampus and related structures that co-occurs with hippocampal theta oscillations and is thought to function to coordinate activity between distant structures
How many afferents are there per cochlea?
30,000
listening phase in zebra finches
30-60 days after hatching, listening
How many cells of each type in the rat CA3 and CA1?
330 thousand pyramidal cells in CA3, 420 thousand pyramidal cells in CA1 and various interneurons in both
How long is the cochlea in humans?
33mm
What is the scale of cortical areas?
3cm
How many newborns are born with a hearing disorder?
4-6 out of every 1000
What percentage of adults over 75 are hearing impaired?
40%
The middle ear works for which frequencies?
500 - 2,000Hz
In what frequency range is the auditory system maximally sensitive?
500 - 5,000Hz
What is the frequency range of speech sounds?
500 - 5,000Hz
hippocampal theta oscillations
6 - 10 Hz large amplitude oscillations in local field potential that is observed during exploratory and attentive behaviour, which reflect highly precise spike timing throughout the hippocampal structures
Around what age does the human critical period for auditory cortex development close?
6 - 7 years
When in development of humans does the perception of words, sounds, and syllables mature?
8 - 10 months
What is the density of synapses in the cerebral cortex?
9 x 10^9 / mm^3
crystallization of zebra finch song
90 days after birth, song is no longer plastic (stereotyped song)
Afferent and efferent connections to hair cells overview
95% of afferents contact inner hair cells, while the other 5% contact outer hair cells. Each inner hair cell has contacts with about 10 afferents, allowing for sharp pitch description. In contrast, outer hair cells are only contacted by a single afferent fibre, leading to more broadly tuned sensations. Outer hair cells also receive 95% of efferent input.
episodic buffer
A component of working memory where information in working memory is put into logical sequences to create coherent memory
the role of the amplitude in a sine wave describing visual brightness
A controls the contrast of the stimulus
random dot stereogram
A pair of stereoscopic images made up of random dots. When one section of this pattern is shifted slightly in one direction, the resulting disparity causes the shifted section to appear above or below the rest of the pattern when the patterns are viewed in a stereoscope.
rat experiment with shock to test hippocampal memory encoding from episodic to semantic memory
A rat is shocked by the floor. A normal rat will exhibit freezing behaviour when put back into this same room because he knows that this is where he was shocked. When the hippocampus was lesioned, the animal didn't freeze. However, when the animal was shocked 28 days in a row, the animal finally froze as much as the control animal. This would indicate that it takes around 28 days for episodic memory to become semantic memory. Another study found that it took almost 100 days or the info to become semantic memory in the cortex.
AB fibre length in the spinal cord
A single axon travels along many segments of the spinal cord and doesn't just stay local
Grid cells in the dorsal MEC
A single neuron in dorsal MEC is receiving inputs that allow it to keep track of how much distance the animal has travelled in all particular directions, forming fields with equilateral triangles between each of the fields.
How can the correlation between spontaneous spiking in resting states and evoked states make sense at the single neuron level?
A single neuron that prefers horizontal orientations, for example, is part of an assembly in the visual cortex that responds preferentially to those gratings. This same neuron would also be active as part of an assembly during the correlated spontaneous activities. We can see this because the neuron has an increased firing rate whenever the correlation coefficient is high. We see that this single neuron prefers a specific orientation, not only during response, but also during spontaneous activity. It is more likely to fire when the pattern of population activity corresponds to the pattern of population activity obtained by stimulating with the neuron's optimal orientation stimulus, regardless of if this neuron was stimulated or not.
How does the physical deflection of hair cells affect receptor potential?
A very small physical deflection causes a big depolarization.
optogenetic activation of hippocampal memories
A virus was injected into the dorsal hippocampus that caused channel rhodopsin to be expressed when no doxocyllin was present in the animal's diet. The virus is only expressed when c-fos promoter is transcribed, which happens when the neuron is highly active. When dox was removed from the animal's diet, c-fox is expressed and thus so is channel rhodopsin. This lets you tag neurons that were active the day you take out dox from the animal's diet.
What is the result of norepinephrine on the heart?
AP is shortened
motion direction selectivity in the visual cortex
About 25% of V1 cells have motion direction selectivity and care about the direction the stimulus is moving
What was seen in mice injected with hM4D?
Activation via CNO silencing PV neurons led to a reduction in the withdrawal threshold, implying that PV neurons are actively involved in blocking touch inputs that cause pain
experiment decoding position from place cell activity and during sharp-wave ripples
An algorithm was developed so that the decoder guesses where an animal is based on previous data. It showed that it was very accurate in coding place cell activity. Later, this same decoder was applied during sharp-wave ripple events and it was seen that the decoder guesses the animal is reproducing the same sequence of movement as it did when the animal was actually moving. It was able to replay events 4 - 5mm long.
experiment that looks at gamma coherence between LEC and distal CA1
An animal had to go into a port, where it was exposed to one of two odours. The animal would typically learn where the doors were. It was found when recording from the LEC and dCA1 that there was strong coherence between the signals. There's no coherence between MEC and dCA1, though or between LEC and pCA1 because those structures are not directly connected. More evidence suggesting that successful performance requires coherence between LEC and dCA1 is that when an animal makes an error, the coherence is reduced.
temperature regulation
An integrator in the hypothalamus integrates autonomic, endocrine, and skeletomotor response through peripheral and central receptors. There also exist warm and cold sensitive neurons in the pre optic area. The hypothalamus coordinates autonomic, endocrine, and skeletomotor responses when there is deviation from a biological set point.
How are place cells generated?
Animals can still generate place cells even when NMDA receptors are blocked. But, LTP seems important for anchoring place or location map across days. Place cells still existed after cutting Schaeffer collaterals. The entorhinal cortex shows weak spatial coding.
Why would it be beneficial to reduce correlated noise?
Any one stimulus is activating lots of neurons, leading to lots of action potentials, so the brain will average this info to get a better idea of what's true. But this only works if noise is independent because with even a tiny bit of correlation, you start to saturate the amount of info given with more and more neurons (so more neurons is no longer helpful). As you reduce correlations, the amount of info you get is scaled with the number of neurons so that you get more info.
Spinal cord stimulation procedure
As the patient lies face down under anesthesia, a surgeon places a guide needle into the epidural space between vertebra. while an x-ray is being taken. Two stimulation electrodes are put on the dorsal surface of the spinal cord in the region where info comes from the site of allodynia. After the electrodes are placed, the patient is slowly brought out of anesthesia. Does she still feel pain? Yes, she did. They try stimulating electrodes at different points, frequencies, amplitudes, while she says what she feels. When they reach the right spot, the patient exhaled cause she felt no pain anymore. They found the proper stimulation parameters, frequency, everything. The patient is sutured back up with a battery. After a month or so, they check with the patient and if she still has no pain, insert new long-term battery that can last years.
What going on with the utricle and saccule?
As we move, the epithelium is moving, but the mass of calcium crystal on top of the stereocilia leads to a lag of epithelia, which causes shearing. In one direction, movement causes excitation, while it causes inhibition in the other direction.
connection between input and output for hippocampal place cells
As you change the input to the system, you get nonlinear output in sigmoidal way.
pattern completion vs. pattern separation
As you change the sensory input to a system, the perception changes in a sigmoidal way from pattern completion to pattern separation.
orientation tuning in all layers of the visual cortex
As you descend the layers (perpendicular to the surface of the skull), the orientation will remain the same in a column. If you sliced at an angle, the preferred orientation would change smoothly.
What's going on in the semicircular canals?
As you move, fluid moves within the semicircular canals, pushing on the membrane, causing a deflection of the stereocilia. Moving one way causes excitation, while moving the other way causes inhibition.
What is the first division of sensory neurons and when does it occur in embryonic development?
At days 10-12, you see that there are the RUNX3 / trkC neurons and the RUNX1 / trkA neurons.
How does sound localization by interaural level differences work?
At high frequencies (>3,000Hz), the head casts a shadow relative to a sound source, such that the sound is quieter at the ear further from the sound source.
So, how do tonopy (place coding) and phase locking work together to allow for the discrimination of frequencies along the basilar membrane? (duplex theory of pitch and loudness discrimination)
At high frequencies, place coding is used based on the place where the basilar membrane is maximally excited and the number of spikes increases with loudness. At low frequencies, much broader areas of the basilar are moved, so phase locking must be used since burst frequency can specify frequency and the number of spikes in a burst specifies loudness.
How does sound localization by interaural time difference work?
At low frequencies (below 1,500Hz), the difference in arrival time at the ear can be used for sound localization. Sound reaches the ear nearer the sound source first and it takes 1ms to travel from one ear to the other.
Why does the Hermann grid illusion work?
At the spots where the grid intersects, there is less brightness perceived because if we assume that this is an on centre / off surround retinal ganglion cell, then the white in the surround acts in an inhibitory way so that the centre of the grid intersection doesn't seem as bright. At other white lines on the grid, there is more darkness in the surround, so these lines appear to be a brighter white.
visual attention
Attention increases neuronal and perceptual sensitivity to stimuli that aren't very salient. Attention is like turning up the volume of a stimulus, in terms of getting a response.
Attention and neuronal responses
Attention increases the amplitude of tuning curves, without changing their shapes (increases as one ascends the cortical hierarchy)
So what does attention do on a neural level (example with monkeys and V4 neurons being measured)?
Attention increases the number of action potentials fired in response to a particular stimulus (doesn't affect neuronal selectivity for different orientation or anything though)
How does attention relate to correlated noise between neurons?
Attention reduces correlated noise between neurons in the visual cortex.
What is a BOLD response?
Blood oxygenation level dependent signal
connecting attention to signal detection theory
By attending, you increase the rate of neural activity, which increases d'. This means that there is less overlap between the actual and desired distributions so that fewer perception errors will be made.
What projects to layers V and VI of the entorhinal cortex?
CA1 and the subiculum
CA1 spatial place fields
CA1 pyramidal cell firing is location dependent (stable over time, assuming no changes in the environment)
associational commissural pathway
CA3 neurons that send axons to CA1 cells in the contralateral hippocampus
hM4D mutated receptor
Can be injected as a virus to silence PV neurons when CNO is injected
meatus in children
Children have a shorter meatus, meaning that higher frequencies pass better and sounds seem louder for children.
chloride extrusion, as it relates to neuropathic pain
Chloride extrusion increases KCC2 activity, thus increasing the driving force, so that GABA will cause an even more hyperpolarizing response than usual. (Chloride extrusion means that there will be little chloride in the cell, so that when GABA channels open, the influx of chloride that causes the hyperpolarization, will be even greater.)
difference between achromatic and colour-coded retinal ganglion cells
Colour-coded retinal ganglion cells are not inhibited by the opposite colour being in its incorrect field (centre or surround). Therefore, achromatic cells represent the amount of centre stuff plus the amount of stuff in the surround, whereas chromatic cells take the difference of the inputs.
What is the result of the ice cube model of the primary auditory cortex?
Columns are responsive to every audible frequency and each type of interaural interaction.
Cochlear nucleus
Contains 3 subnuclei, each of which has an orderly tonotopic map, organizing frequencies from low to high before sending info to higher brain centres. Globular bushy and spherical bushy cells can maintain the timing information to compute sound localization in space.
Is it easier to tell what an object is when given the curved lines or the straight lines of the object?
Conveying info by sending the smallest number of inputs is obtained by using curved lines
What does CA stand for in the hippocampus?
Cornu Amonis
mouse model of nerve injury-induced mechanical allodynia
Cut common peroneal nerve and sural nerve, but leave the tibial nerve intact and see that the mouse gets allodynia by stimulating with Von Fry filaments at different intensities before and after nerve injury and measuring pain threshold
Does BOLD response reflect spiking activity?
Detected linearity doesn't mean that spikes cause the hemodynamic response. It is possible that synaptic activity causes the BOLD response, not APs.
What is the future for reducing those affected by hearing loss?
Developing better hearing aids and prosthetics, finding new methods for protection, and discovering hair cell regeneration
How can one compare the brain's functional architecture during activation and rest?
Do fMRI on resting state patients. Compare the imaging with the imaging in BrainMap when patients were doing specific tasks. Compute the correlation in the spatial domain. See which areas are co-active for a given task and compare to resting state networks. It was found that co-active areas in the active state are also correlated in the resting state.
binaural summation columns
EE neurons excited by stimulation of either ear
effect of 1Hz tetanus on Schaffer collaterals
EPSP strength is reduced, showing that LTD took place
1st wave of migration of crest cells
Each crest cell will divide into 3 neurons, generating mostly large neurons, mechanoreceptors and proprioceptors.
hippocampal sharp-wave ripples trigger activity throughout the whole cortex
Electrodes were implanted in monkeys and fMRI scanning was done. It was seen that during ripples, many structures were activated, while many structures also experienced inactivation. Subcortical areas seemed to be mostly inhibited, while cortical areas seemed to be excited. For example, if you recorded from V1 while recording from hippocampal neurons, you could see a replay of hippocampal neurons and replay in V1, showing that hippocampal replay is driving replay across the whole cortex.
Motivational states are driven by what?
Elementary drive states and complex physiological regulatory forces and personal or social aspirations acquired by experience
What are the implications of the rat experiment "Environment Noise Retards Auditory Cortical Development?"
Environmental noise could contribute to auditory and language-related delays in children. This can occur in conditions like chronic otitis media and when a cleft palate closes the Eustachian tube.
What does parallel fibre stimulation show us in terms of the source of the BOLD signal?
Even when the APs of Purkinje cells are reduced, CBF increases, so the hemodynamic response doesn't depend on AP. It does depend on excitatory, inhibitory, or mixed synaptic response, though.
Talairach system
Find the anterior and posterior commissures and define 0,0 as being at the anterior commissure. Define a horizontal axis that goes from the posterior to the anterior commissures. Make sure the brain is straight. Check the maximal coordinate on x, y, and z axes and normalize the size accordingly.
Place code of auditory afferents
Frequency is tonotopically arranged and afferent info is not redundant, since most auditory nerve fibres respond over a range of only 40dB, so we need different afferents with different thresholds for amplification for the same frequency.
So, how is PV activity being reduced in cases of nerve injury if the neurons aren't dying?
From fluorescent tagging with WGA and microscopy, it's been proposed that PV neurons retract their terminals from the soma of PKCgamma neurons, but some terminals must still be there since analgesia is seen when PV neurons are enhanced.
somatomotor resting network
Functional connectivity can be shown through fMRI by looking at which areas have statistically similar spontaneous fluctuations in the resting state. For example, the left and right somatomotor cortex match very well, despite being far away in the brain.
inhibitory interneurons
GABAergic neuron
Golgi vs. Weigert staining
Golgi stains grey matter, while Weight stains white matter, displaying the 6 layers of the neocortex
Head direction cell development in rats
Happens very early in development and is seen as early as 3-4 days before eyes even open
What happened to patient HM?
He had his hippocampus, amygdala, and other multimodal regions removed through a lobotomy. After this, he had a problem forming explicit (declarative) memory, but remembered facts and events from before the surgery. His implicit memory, however, was still intact as he could improve at the star task day by day, even if he didn't remember doing it. He could also remember word lists with the help of priming.
Anticipatory firing of head direction cells
Head direction cells in the anterodorsal thalamic nucleus (ADN) shift towards the direction you're turning
2nd wave of migration of crest cells (late wave)
Here, there is the highest rate of proliferation. On crest cell produces 36 fully specified neurons, forming all 3 types of sensory receptors. Many of these neurons form the dorsal root ganglia.
3rd wave of migration of crest cells
Here, there is the migration of boundary cap cells. This wave also produces 5% of dorsal root ganglia neurons. These cells become almost exclusively nociceptors, though some do become glia cells.
Hypercolumns in V1
Hypercolumns consist of pairs of ocular dominance columns, blobs, and many orientation columns. Within a singular hypercolumn, neurons have receptive fields that represent similar locations in space. They're repeated across the visual cortex, so that there is a hypercolumn for every part of visual space.
hypothalamus orchestrating cortisol release along HPA
Hypothalamus is activated, releasing CRH, which activates anterior pituitary to release ACTH onto adrenal cortex, which then releases cortisol, which feeds back to hypothalamus and pituitary to stop the release of CRH and ACTH
What happens to outer hair cells in cases of hypoxia?
Hypoxia reversibly inactivates outer hair cells.
How do evoked and spontaneous otoacoustic emissions work?
If the basilar membrane is moved, fluid will move, push on the middle ear bones, pushing on the tympanic membrane, pushing sound back out of the ear into the air.
How does navigating mental space relate to grid cells?
If you can explore concepts in 2D mentally, you can run the same analysis to see if walking through mental space at a 60 degree angle produces the same neural activity because memory isn't just about space. So, grid cells might help with conceptual space coding.
Influence of touch on speech processing study
In 2009, researchers from UBC found that puffs of air accompanying sounds starting with "p", "t", and "k" influence our perception of sound such that applying a puff of air with "ta" or "da" sounds lead to misidentifying the sound.
medial superior olive
In MSO, there are neurons that are receiving inputs from both ears, but with a longer axon comes a longer delay. The neurons in the MSO are coincidence detectors, meaning that they will only fire if activated by both ears at the same time. Each neuron in the MSO signals a different interaural time difference, which is mapped such that it can be sent to higher processing centres.
opening of polysynaptic excitatory pathways from deep to superficial dorsal horn, as it relates to chronic neuropathic pain
In all individuals, there exists wiring of large myelinated AB touch neurons to the projection neuron. In healthy people, this input is inhibited by inhibitory interneurons. But after nerve injury, it can be found that there is decreased function of these inhibitory functions (either dead or retracted nerve terminals or less transmitter), such that the input from AB fibres isn't blocked. This means that allodynia occurs.
redundancy
In natural images, nearby pixels have very similar values.
lateral superior olive
In the LSO, each neuron is sensitive to interaural level differences as input from the bushy cells of the CN is received. There is an excitatory response when the sound is from the ipsilateral side, but there is inhibition from MNTB on the contralateral side.
Ear infection
Infection that blocks the Eustachian tube, causing the buildup of fluid in the middle ear that is more common in children because the middle ear is anatomically more accessible to bacteria
method to control activity of PV neurons in a spatiotemporal manner
Inject a virus with that codes for hM3D but inverted, so Cre has to flip it so that it can be transcribed. Now, only PV neurons in that zone will express hM3D, so that you can inject the animal with CNO and see what happens after turning on PV neurons
method of photoreceptors converting light into electrical signals
Inside photoreceptors, there's a sodium / potassium pump that works in the dark, allowing sodium to flow in and potassium to flow out. When light hits the photoreceptor, it sets off a cascade that decreases cGMP in the cell, causing the closing of sodium channels, allowing the cell to hyperpolarize due to the outflux of potassium.
Why is endstopping in V1 useful?
It can detect things that are curved because curved lines wouldn't shut off the response cause curved lines would avoid the inhibitory regions
hypotheses on the role of default mode network
It features ongoing processes surrounding consciousness and awareness, self referential processes, and introspection. Altered default mode network activity is seen in sleep and in cases of mild cognitive impairment, such as Alzheimer's disease, Schizophrenia, and depression.
What is the point of language?
It is a code for transmitting ideas based on words and grammar.
Pearson's correlation coefficient
It is a measure of linearity from -1 to 1 that is used to measure functional connectivity. Correlation goes down if there is more noise (< |1|)
How is blood flow controlled in the brain?
It is controlled by cortical blood vessels through arteriolar smooth muscle and pericytes on capillaries, which control dilation or contraction of blood vessels.
How is direction selectivity constructed in V1?
It is derived from LGN inputs that are shifted in space and delayed in time
spontaneous fluctuations in fMRI signals
It is found that in a resting state, a patient shows large amplitude fluctuations in the cerebral cortex on the scale of 0.01 - 0.1H
Where is phase precession observed?
It is observed in entorhinal layer II, but not layer III grid cells. In layer III, phase locking occurs where spiking is locked to the peak of the theta oscillation.
What property of deoxy-HB lets us use it to measure neuronal activity through fMRI?
It is paramagnetic, meaning that it is a relatively weak magnet that acts as a contrast agent. This means that when you have a larger proportion of deoxy-HB to oxy-HB than normal, the deoxy-HB has strong enough magnetic properties to cause changes in the homogeneity of the magnetic field.
continuum from stimuli in IT
It is possible to establish a continuum from stimuli that are just faces to stimuli that are other objects by adding noise.
What does ECT actually do physiologically?
It may contribute to neurogenesis in the hippocampus, enabling more negative feedback. It may also act on NMDA receptors (ketamine blocks NMDA and has seen to reduce depressive symptoms for weeks)
Is orientation selectivity innate or developmental?
It must be developmental because a young animal responds about the same to every orientation, but an animal that has never experienced orientations will fail to develop columns with vertical orientations, but can still figure out horizontal orientations.
So, what does the BOLD response reflect?
It reflects a local increase in neural activity assessed by the mean extracellular field potential signal. It reflects changes in LFP (synaptic activity), input to, and local processing in a region, more than it represents MUA / output in a region.
3D coding of head direction cells in bats
It was found that head direction cells are in toroidal coordinates in bats (purely azimuth).
What happened when multi-unit activity was dissociated from the BOLD signal?
It was found that when a visual stimulus was modified, the BOLD response followed the duration of the stimulus, as did the LFP (a reflection of synaptic activity). In contrast, the MUA and spike density responses remained transient, showing that they were not responsible for the hemodynamic response.
What happens with realignment of entorhinal grid cells?
It was found that when entorhinal grid cells are realigned (shifted in phase), global remapping occurs
tracer injection
It's a way to determine anatomical connectivity in the brain. BDA is an example of a tracer put in V1 of a mouse to see which other areas of the brain get axonal projections from V1.
How could boundary vector cells relate to place cells?
It's possible that a population of boundary vector cells could all send their inputs to the hippocampus, where they could be summed to create place fields. Wherever boundary vector cells intersect, there could be a place cell. This makes sense since boundary vector cells still work when the medial septum is inhibited. But the problem is that the majority of boundary vector cells are right along the border, which would imply that place cells should be more just on the borders of placed. So maybe boundary vector cells and grid cells work together to create place fields.
logarithmic loudness function
L = 20log(P / Pstd)
single-opponent LGN cells
LGN cells have excitatory responses to one colour in the centre and inhibitory responses to the opponent colour in the surround
overall requirements for LTD and LTP
LTD requires moderate NMDA activation and moderate calcium elevation, while LTP requires strong NMDA activation and high calcium elevation
STDP
LTP and LTD are dependent on spike timing in the pre and postsynaptic cells pre before post induces LTP, while pre after post induces LTD
Parvalbumin neurons
Located in lamina III of the dorsal horn, seem to synapse on PKCgamma excitatory interneurons and on AB fibres. There's a hypothesis that PV neurons can be activated through SCS by AB fibres to block allodynia. (This could be a pharmacological way to treat pain without surgery.)
How can we figure out pain pathways, step by step?
Look at one subset of neurons at a time, using mutagenic mice injected with tracers. This will let us sort out the role of interneurons and their connectivity in healthy and pathological conditions.
Optic flow is encoded by which region?
MST - translations, rotations, and expansions
complex motion tuning in MST
MST neurons respond to complex patterns of visual motion because their receptive fields are large enough to integrate the full-field stimulation caused by motion of the observer. (receptive fields often include parts of the ipsilateral visual field)
stimulus size selectivity in MT
MT doesn't get much info about straight line edges that are very long, participates in endstopping
Early and later directional MT cell response
MT initially encodes the component of motion perpendicular to bar orientation, with different tuning curves for parts of an object moving at same velocity cause of the aperture problem but later, the MT neuron has figured out the correct direction of motion
What are the components of the mean extracellular potential?
MUA and LFP
cortical magnification factor equation
Mc = A / (E + k), were E is position on the retina, and A and k are constants (E = 0 is the fovea)
What happens to memory consolidation if hippocampal sharp-wave ripples are inhibited?
Memory consolidation is screwed with. This was seen in a rodent experiment, in which the animal had to remember where food was. When a ripple was detected, a pulse was played to stop this activity and it was found that these animals performed worse.
What happens with calcium after nerve injury?
Microglial cells release cytokines like TNFalpha that binds TNFR1, triggering a signalling cascade that downregulates PV protein. This means that calcium won't be chelated, so it will accumulate, turning on potassium channels, slowing down the inhibitory output
high vs. low spontaneous rates of afferents in the auditory system
Most sensitive afferents have a high spontaneous rate. You need afferents at all spontaneous rates, though, because there needs to be an afferent for different amounts of stimulation at the same frequency.
sensory input to the ANS
Most sensory info from visceral organs reaches brain through the vagus nerve and visceral sensory info from the head and back enter the brain through the glossopharyngeal and facial nerves, which synapse in brainstem nuclei
How do nicotinic and muscarinic acetylcholine receptors compare?
Muscarinic receptors are slower acting cause they work through 2nd messengers
Dreadds way of activating neurons
Mutate ACh binding site hM3D, so that there is a new binding pocket for CNO. CNO ligand can be injected and will cross the blood-brain barrie, activating a GPCR that lets us turn on neurons where hM3D is expressed
What are the two types of afferents relating to hair cells?
Myelinated, type I auditory nerve fibres contact inner hair cells, while unmyelinated, type II auditory nerve fibres contact outer hair cells.
significance of NGN1
NGN1 is expressed in most dorsal root ganglia cells. It initiates the 2nd wave of neurogenesis in the dorsal root ganglia. NGN1 produces small trkA neurons, as well as large trkB / trkC neurons in the dorsal root ganglia
significance of NGN2
NGN2 initiates the 1st wave of neurogenesis, which stays expressed until dorsal root ganglia form. It is NGN2 that produces trkB / trkC mechanoreceptive and proprioceptive neurons.
theta rhtymic autocorrelation
Neuron tends to burst fire at every peak of a theta oscillation and the inter burst interval is at theta frequency
Is there a loss of PV neurons following nerve injury?
No, it is clear that although something is happening to them, they're still there cause they show up with tdTom staining
Is there just one type of interneuron in the dorsal horn?
No, of course not! Even within the inhibitory subset, there are many different types.
Is perception a direct record of the external world around us?
No, perception is constructed internally according to the constraints in the architecture of the nervous system and its functional abilities
Do hair cells fire action potentials?
No, they produce a graded response caused by the release of glutamate onto afferents.
noise and memory
Noise is a key distractor and has adverse effects on working memory.
primary afferent depolarization as a method of presynaptic inhibition
On primary afferents exist NKCC1 channels that pump chloride inside the cell, hyperpolarizing it. As such, when GABA binds o the nerve terminal of AB fibres, the concentration of intracellular chloride being so high results in depolarization of the AB fibres, but this reduces neurotransmitter release. This is because at a hyperpolarized state, this depolarization isn't enough to reach the AP threshold. Nevertheless, this depolarization causes the inactivation of sodium and calcium channels, disallowing them from propagating any AP there may be.
How does adaptation of hair cells work?
Once the cell is depolarized and there is an influx of calcium, there exists a myosin motor molecule that controls the tension of tip links to let go, closing channels. In contrast, if there's less calcium, the motor molecule can climb along actin to increase tension, opening some channels.
What happens when you measure from multiple place fields and compare to theta oscillations?
One finds that the 2nd place field doesn't start firing til the 2nd theta peak, but phase processes till it goes 360 degrees. We now have a spike timing relationship between 2 cells. As you add more place fields, you see that within a single theta cycle is a sweep of activity that represents places behind you and in front of you. This allows for precise temporally structured cell assemblies.
What happens to outer hair cells when depolarized or hyperpolarized?
Outer hair cells shorten when depolarized and lengthen when hyperpolarized.
What causes phase precession?
Phase precession is the result of the neuron oscillating faster than the extracellularly recorded theta oscillation. It was found when recording intracellularly, however, that intracellular theta peaks are moving earlier and earlier in phase, which is caused somehow by the speeding up of internal place cells.
How are hair cell tuning curves obtained?
Play a tone at a given frequency and increase the amplitude until the hair cell response is 1mV.
What are BOLD responses in V1 actually showing us?
Positive BOLD responses in human V1 are proportional to average firing rates in the corresponding area of the monkey cortex. This was determined experimentally.
How does power spectrum correlate with spatial frequency?
Power spectrum declines as spatial frequency increases
What molecule is requires for electromotility in outer hair cells?
Prestin, an anion transporter that allows for direction voltage-to-displacement conversion
3 primary brain vesicles
Prosencephalon (forebrain) Mesencephalon (midbrain) Rhombencephalon (hindbrain)
cerebellar anatomy connections
Purkinje cells get input via parallel fibres from granule cells large climbing fibre exists through the layers granule cells get mossy fibre input
Demonstrating the sigmoidal curve between input and output of place cells
Put an animal in the same place, but slowly change the input. Morph the box the animal is in until there is sudden switch to circular representation. It is at this point that the system is pattern separated.
Which transcription factor family in particular controls the expression of trk receptors?
RUNX
Morris water maze
Rat experiment in which the animal is placed in a tub filled with chalky water, so that it can't use cues to find a hidden platform. It must learn where the platform is hidden.
rat feeding behaviour set point experiment
Rats were starved and then their weight went back to set point once provided food again. Rats were force fed and then. their weight went back to set point once allowed to eat as it liked again.
rat experiment "explicit memory creation during sleep demonstrates a causal role of place cells in navigation"
Recordings of place cells were done in an open field environment. Every time a neuron fired while the animal was asleep, it would send an input to the medial fibre to a dopaminergic receptor. When the awake rat was put in the same environment as before, it ran to exactly the same location as where the place cell was. This shows that memory can drive reward-seeking behaviours.
Rat experiment "Environmental Noise Retards Auditory Cortical Development"
Recordings were done from rat auditory cortex to measure their frequency selectivity. It was found that in immature rats, more neurons respond to high frequencies, but once the animal is mature, all frequencies are equally represented in the auditory cortex. But, when sound of a specific frequency was played to an immature animal during the critical period, there was an overrepresentation of cortical space to that frequency. When a loud broadband noise was played before the rats could even begin to hear, the auditory cortex was unable to develop properly and there was still a very immature-looking cortex with an overrepresentation of high frequency sounds, even once the animal grew up. Experimenters then began to introduce a 7kHz noise after 50 and 90 days of broadband noise. They found that the cortex subsequently developed more area dedicated to this frequency, indicating that the critical period was still open after playing this broadband noise. This means that whatever signal is causing the closure of the critical period relies somehow on some type of coherent stimulus.
BDNF
Released due to the activation of microglia, goes and binds to TrkB, leading to the downregulation of KCC2 channels
effect of vestibular inputs on head direction cells in ADN
Semicircular canals are important for translating movements to create head direction signal.
simultaneous spatiotemporal imaging of blood-oxygenation and neurophysiological signals
Shine light at 630nm, which both excites voltage-sensitive dyes, but can also be used for neurophysiological signals cause the absorption of oxy-HB and deoxy-HB is different under 630nm. The intrinsic signal will be inverted with a dichroid mirror, so that one camera will figure out the signal based on voltage-sensitive dyes, while the other will look at the intrinsic physiological signals.
How does the simple cell model work?
Simple cells have separate receptive field regions that respond to light and dark stimuli, allowing one to predict the response to a more complicated stimulus through mapping of the subregions.
What connections drive slow gamma hippocampal oscillations? (~40Hz)
Slow gamma reflects CA3-CA1 synchrony
What might contribute to cochlear amplification, other than outer hair cells?
Stereocilia could be oscillating at the characteristic frequency of the hair cell, allowing them to best signal that frequency.
So, what is being stimulated with spinal cord stimulation?
Stimulation electrodes are placed above the dorsal column, stimulating only AB fibres, which activates the inhibitory interneurons of the spinal cord.
tripartide synapse
Synapse pre and post terminals are wrapped by glial cell processes that sense the level of activity. When there's excessive activity, ATP is released from a channel on microglia membranes, setting off a signalling cascade during which BDNF binds to its receptor TrkB on projection neurons. This TrkB activation leads to the downregulation of KCC2, letting chloride accumulate so that inhibitory inputs cause depolarization.
What kind of mechanically gated channels do we have in hair cells?
TNC1 and TNC2
Signal to noise ratio for neural and hemodynamic signals
The SNR of neural signals was much higher than that of the BOLD response. This means that fMRIs likely underestimate a great deal of actual neural activity related to the stimulus or task so an fMRI should be repeated numerous times.
What happens to the responses of afferents in the auditory system when there is noise?
The afferents respond less in noise due to adaptation to this constant noise stimulus.
Lesion to the ventral hippocampus in Morris water maze experiment
The animal can still find where the platform was.
Lesion the whole hippocampus in Morris water maze experiment
The animal can't find where the platform was.
Lesion to the dorsal hippocampus in Morris water maze experiment
The animal has no idea where the platform was.
No lesion in Morris water maze experiment
The animal learns where the platform is. Even once the platform is taken away, the animal keeps swimming around where he'd learned the platform was.
fear conditioning in rats with optogenetic activation of hippocampal memories
The animal without dox was shocked, so that place cells were expressing channel rhodopsin. This lets you stimulate those neurons later to artificially drive animals to freeze by using light. This shows that place cells are driving memory because when they are reactivated, the animal remembers what happened in that room.
MT and the aperture problem
The aperture problem arises when bar orientation isn't perpendicular to motion direction.
Using perspective to convey depth
The brain can rely on the perspective of the image to relay information about depth
spatial correlation of natural scenes
The brightness between pixels often doesn't change much from pixel to pixel beside it. The correlation declines with distance.
Is cochlear amplification sharpest at low or high amplitudes and why?
The cell can only move so much so it amplifies best for low amplitude sounds.
What happens when recording from a boundary vector cell and a new wall is inserted into the environment?
The cell still codes boundaries on that side (for example, now codes both left boundaries)
What happens when recording from a boundary vector cell when the box that a rat is in is expanded?
The field expands.
temporal code of afferents in the auditory system
The firing of a neuron can be based on the frequency of the auditory stimulus. The firing may not occur for each cycle, however. Phase locking is important at low frequencies, under 4,000Hz. The AP is always fired at the peak of the sine wave.
Plot firing rate vs. sound level of afferents
The firing rate increases with sound level, forming a sigmoidal curve, showing saturation.
frontal cortex and emotion
The frontal cortex provides a conscious response to bodily states and its entire removal can calm chimpanzees
What can be said about the temporal relationship between the hemodynamic response and the neurophysiology?
The hemodynamic response recorded from voltage-sensitive dyes lags behind because this response is mainly obtained from larger vessels like veins, rather than venules or capillaries. This shows that the hemodynamic response is slower than the neural activity.
hippocampus and emotions
The hippocampus affects emotions cause it encodes the emotional content of memories as well.
Anatomically, what makes the hippocampus so different from the cortex?
The hippocampus has tightly packed cell layers, while the cortex has cells everywhere.
What happens if you apply calcium chelator to tip links?
The link is broken and the cell can no longer respond to any deflection.
mechanical amplification of the middle ear
The movement of the ossicles creates a 1.3x increase in pressure due to the "lever arm" of the ossicular chain
induction of neurons in the neural crest
The neural crest is between the ectoderm and the neural tube. Signalling factors like BMP and WNT start to be produced, preparing cells to migrate.
pressure amplification of the middle ear
The oval window is much smaller than the tympanic membrane, so when the stapes transfers the pressure from the tympanic membrane to the cochlea, the same force produces a pressure that is 17x greater (since pressure = force / area).
visuospatial sketch pad
The part of working memory that holds and processes visual (extrastriate cortex) and spatial (parietal cortex) information
cochlear prosthesis
The prosthesis is implanted through the round window and an electrode is placed within the scala tympani. Around 12 electrodes are spaced along the cochlear spiral to stimulate groups of auditory nerve fibres that respond to different frequencies. This requires that auditory nerves are intact, but bypasses hair cells.
How do we know that otoacoustic emissions aren't just echoes of what is played into a patient's ear?
The responses from different patients are all at different frequencies and timing.
What happens to young children who have their left hemisphere removed?
The right hemisphere can develop language relatively normally
So, how does a spontaneously occurring pattern similar to an evoked pattern compare to an actually evoked pattern?
The spontaneously occurring pattern has an amplitude of about 70% that of the evoked pattern.
What is the sequence of events that occurs at the level of the hair cell during hearing?
The stereocilia are deflected, opening ion channels, letting in cations like potassium, depolarizing the cell, activating voltage-gated calcium channels, causing a calcium influx and neurotransmitter release, causing the 8th nerve to fire an AP, sending info to the brain.
basic circuit that controls emotions
The stimulus info goes to the neocortical (frontal and singular cortex) and subneocortical (thalamus and amygdala) processing centres, which also exchange info. The info in turn goes from the neocortical and subneocortical processing centres to the skeletomotor and autonomic control systems, which sends info to the periphery. The periphery ultimately feeds back one the neocortical and subneocortical processing centres.
auditory curve, as shown by Fechner and Stevens
The threshold lowest for frequency ranges that overlap with the human voice. The y-axis is intensity, measured in decibels and the x-axis is frequency. For every 10dB, you perceive the sound as twice as loud. (If the sound pressure goes up by a factor of 3, that would get us from 20dB to 30dB, which is perceived as twice as loud.)
What is the volume of the human hippocampus like, compared to the rat and monkey hippocampus?
The volume of the human hippocampus is about 100 times that of the rat and 10 times that of the monkey.
How do spectral cues work for sound localization?
The way sound is bounced around the pinna is varied depending on if the sound is coming from higher or lower.
proprioceptive neurons' connection to the spinal cord
Their axons enter the spinal cord at the dorsal column and go to deep layers. Proprioceptors are also found in the ventral horn intermediate zone.
What happens once the neuronal sub-types are specified?
Their central terminals will project towards the spinal cord.
What happens to mice with a knockout for Prestin?
Their outer hair cells don't move and there is a 40dB loss in auditory sensitivity.
hexagonal grid of fields in dorsal MEC grid cells
There are 3 primary axes, organized at 60 degree intervals.
Ion channel properties of hair cells that relate to frequency in lower vertebrates
There are faster mechanically-gated channels in high frequency cells. There exists coupling between calcium channels and calcium-activated potassium channels, since calcium influx activates calcium-activated potassium channels that depolarize the cell. Tuning is determined by the number of channels, isoforms, and the time course of calcium buffer by the cell.
interneurons of CA3 and CA1
There are many types of interneurons interspersed in the hippocampus.
time course of fMRI BOLD response (phases and what happens during these phases)
There exist 3 phases. First, there is the initial phase where the initial peak goes down, since oxygen consumption dominates before blood flow kicks in. Next, there is the positive blood response. This is the main phase used in fMRI and is dominated by an increase in blood flow that washed out deoxy-HB. Finally, there's the undershoot phase that is dominated by CBV that goes back to baseline slower than CBF, meaning that a decrease in the signal is shown.
Receptor potential and mechanoelectrical transduction channels in hair cells
There exist non-selective cation channels, some of which are open at rest. They work over a narrow operating range due to saturation.
conversion from postsynaptic inhibition to excitation, as it relates to chronic neuropathic pain
There exists at the lamina I projection neuron a KCC2 pump. This KCC2 pump functions to actively take chloride from the inside to the outside of the cell. When this pump stops working, there's so much chloride in the cell that a normal inhibitory signal causes a hyperpolarization instead of a depolarization because the reversal potential has changed such that the opening of GABA receptors will now cause the outflux of chloride (instead of influx, like it does in a normal inhibitory synapse).
Mechanically, how does transduction of sound work at the level of the hair cells?
There exists ion channel gating by elastic structures, which is regulated by tension. Bundle displacement towards the longest stereocilia causes increased tension, opening channels, leading to hair cell depolarization.
optimal arousal
There is a certain level of arousal that produces optimal performance and any lower or higher is bad.
What happens if you take a pose and cause a hair cell to move in its positive direction for a long period of time?
There is a deflection caused by the opening of ion channels, before the inward current decays due to adaptation that resets the channels.
What does it mean in signal detection theory when d' is very large?
There is a large difference in the distributions of actual and desired stimulus, leading to almost perfect responses (i.e., hit or correct rejection)
What happens in colourblindness?
There is a mutation that shifts the spectrum of the red cone so that it becomes more like the green type of cone, causing them to overlap, giving you the same output.
What is the significance of theta phase precession?
There is a negative correlation between location and theta phase that increases the precision at which downstream readers can know where the animal is at the single cell level.
What does it mean in signal detection theory when d' = 0?
There is a spread of representations such that you have an equal chance of getting a hit, false alarm, miss, or correct rejection.
With touch, how do ion channels open?
There is literal stretching of the membrane of the cell that causes the ion channels to open.
migration of neurons in the neural crest
There is the reorganization of the cytoskeleton, among other changes. Cells detach from substrate to become mobile and the basal lamina starts to disintegrate. It is the down regulation of N-cadherin and cadherin-6 that causes the changes to cell adhesion properties. Migration starts between embryonic days 8.5 and 10. Neural crest cells start migrating along the ventral pathway to produce cells of the dorsal root ganglion, as well as sympathetic and enteric neurons.
Posner paradigm for measuring the behavioural effects of attention
There was an experiment done in which subjects were told they were going to be presented with a flashed image and an arrow indicated on which side of the fixation point the stimulus would show up. When the cue was invalid (incorrect), subjects had a harder time detecting the stimulus than when subjects were given a valid cue.
What was found in terms of hippocampal oscillations when doing a T maze experiment?
There was an increase in hippocampal oscillations prior to the choice point on an alternation task, right before the animal had to choose which side to turn to.
So, what is going on in osteoarthritis?
There's a loss of cartilage that exposes nerve terminals of nociceptors. This reduces the activation threshold of mechano-sensitive channels at the level of the nociceptor.
So, what is an MRI scanner?
There's a magnet with current flowing outwards. X, y, and z gradient coils allow you to get an image rather than just a linear signal. An RF coil transmits energy to the brain and receives energy back to get an image.
Cushing's disease
There's a pituitary tumour releasing ACTH, leading to lots of cortisol, leading to depression and insomnia as side effects.
Effects of V4 lesions
There's a task in which lines in a circle are tilted either clockwise or counter-clockwise and monkey must state which direction they're tilted. This is encoded by area V1, so V4 lesions have no impact on it. But if there are distractors around, this task becomes very difficult for those with V4 (or TEO) lesions.
Why have mechanical gating for audition?
There's no need for 2nd messengers, so the system is very fast, which is critical for hearing since sound localization is based on small temporal delays and we respond to sounds up to 100kHz
How do we know that cells in the anterior superior temporal polysensory area respond to a conjunction of form and motion?
These cells only respond when the direction a person is facing is in accord with the direction the person is walking.
speed cells in MEC
These provide info about distance cause if you know speed and time, you can calculate distance. An experiment was done with mice where they had to run on a treadmill and it was found that a large percentage of cells in MEC coded for speed
trkA, trkB, and trkC
These receptors are some of the earliest markers of sensory neurons. They serve as receptors for other guidance molecules to attract them to the nerve terminal of the neuron. They regulate the expression of ion channels and other membrane receptors. They also control cell survival during naturally-occurring cell death due to feedforward mechanism. They're also important for the establishment of functional contacts between cells and target innervation.
What is the relationship between the default mode network and the dorsal attention network?
They are anti-correlated functional networks. This means that they show decreases and increases, respectively, during tasks.
What is the time scale using voltage-sensitive dyes?
They are capable of providing linear measurements of firing activity of single neurons, or large neuronal populations with a milli-second time resolution scale.
significance of neurogenins
They bias neural crest cells to the sensory, as opposed to the autonomic lineage. While they can initiate neuronal programs, they cannot further specify neuronal subtypes.
What happens to outer hair cells when exposed to a change in voltage?
They change length!
What is unique about ocular dominance columns in layer 4C of V1?
They exclusively respond to input from only one eye, whereas in other layers, the cells are binocular, though still respond more to one eye than to the other.
rat experiment of feeding behaviour with lesioned lateral hypothalamus
They lesioned the lateral hypothalamus and the rat initially lost weight, but as it recovered, it levels off again but now has a new set point that's lower. They took another rat and starved it before lesioning it, and found that once exposed to regular food again, the animal went to the same level set point as the lesioned animal.
What is generally true of V1 cells with strong disparity preference?
They prefer vertical orientations cause it's easier to detect a different between the eyes with vertical stimuli.
What happens to place cells during sharp-wave ripples?
They reactivate! Place cells are reactivated in the same order or else in the exact opposite order to what they were before.
How do Fechner and Stevens represent intensity of sensation?
They think that the intensity you perceive is not necessarily a linear function of stimulus energy.
transplantation of GABAergic neuron precursors
They transplanted cells from embryonic mice to adult mice with chronic neuropathic pain. This showed analgesic responses.
mechano-sensitive ion channels
They're gated by tension in the membrane, so that when the stimulus engages on ECM and cytoskeleton, the membrane is stretched. When tension increases, the channels open, allowing ions to flow
What do outer hair cells do?
They're responsible for sharp tuning in the cochlea, serving as a cochlear amplifier.
Is head direction coded in 3D in rats?
This doesn't seem to be the case because head direction cells didn't code when the rat was walking on the ceiling of its cage.
boundary vector cell
This is a cell in the MEC that has a big place field with a fixed distance to a boundary. There exists a different population of border cells for each distance from a boundary. There also exists a different population of border cells encoding info in all directions.
locally measured neuronal activity, extracellular recordings
This is how the majority of studies are done, since a neuron is considered to be embedded in an extracellular medium that acts as a volume conductor. As such, when current flows, it must be matched by a similar current in the other direction.
reduced strength of synaptic inhibition, as it relates to chronic neuropathic pain
This is when the inhibitory output is reduced. This can occur due to presynaptic or postsynaptic mechanisms. Presynaptically, there can be decreased neurotransmitter synthesis, the down regulation of vesicular transporters from the nerve terminal, or reduced probability of release. Postsynaptically, there can be a reduction in the number of receptors or their sensitivity.
Disadvantages to blocking pain by blocking nociceptors?
This may not work because we haven't blocked pain transduction at the level of the spinal cord or at the level of the brain, but drugs that try to block at those higher levels have side effects.
What are the advantages to using a cream or injection at the site where the pain is originating on the skin?
This means that the treatment is restricted to a local area and there are fewer side effects.
Gate controlled theory of pain
This model proposes how pain is processed in the spinal cord. It proposes that a projection neuron sends into to the brain, after receiving control inputs from interneurons. It proposes that there is a large touch neuron that sends one collateral to an interneuron in lamina II and another to the projection neuron. It proposes that a small nociceptor sends one collateral to the projection neuron and one sends an inhibitory input to an interneuron. Finally, it proposes that an inhibitory interneuron sends an input to the large touch fibre to block neurotransmitter release, as well as an input to block the transmission of the pain signal to the projection neuron. What is incorrect about this theory is that the nociceptor doesn't inhibit the inhibitory interneuron.
Disadvantages to spinal cord stimulation devices for the purpose of pain alleviation
This requires invasive surgery, which in and of itself carries a lot of risks.
What happens if we apply deflection to hair cells again after they have already adapted?
Those channels still open because the activation let them close so that they could be re-activated by another stimulus.
What comprises the middle ear?
Tympanic membrane, Eustachian tube, and ossicles
How does binocular disparity selectivity work in the visual cortex?
V1 cells look at LGN inputs that have slightly different receptive field positions in the two eyes and different neurons prefer different disparities (near, zero, or far)
illusory contours in V1
V1 neurons respond to real edges in the stimulus, but not to illusory ones
V1 responses and orientation
V1 responses are dependent on the orientation of the stimulus the cells respond very selectively to oriented edges
Where does V4 receive input from?
V1, thin and pale stripes of V2
Where do layers 2 and 3 of V1 project?
V2 and V3, etc. (extrastriate cortex)
What is affected by V2 lesions?
V2 lesions impair the ability to discriminate textures composed of multiple orientations
illusory contours in V2
V2 neurons respond to illusory edges in the stimulus
optical imaging using voltage-sensitive dyes
Voltage-sensitive dyes change their spectral properties in response to voltage changes, so changes in neural activity are accompanied by changes in membrane potential which can be detected with voltage sensitive dyes. These dyes are capable of providing linear measurements of firing activity of single neurons, or large neuronal populations.
Hair cell frequency tuning
We see that hair cells respond best at specific frequencies (can be seen because these cells have a lower threshold at that frequency compared to other hair cells).
What is the ventral visual pathway?
What pathway
How does cerebral blood flow affect BOLD signal?
When CBF increases, we get more oxy-HB, washing out deoxy-HB, causing a more homogenous magnetic field, increasing the BOLD signal.
Mouse osteoarthritis experiment with naive animal
When a low intensity stimulus is given, there's no activation of mechano-sensitive channels. As such, there's no membrane depolarization since the channels never even opened. But if a large mechanical stimulus is presented, the channels will open, causing a depolarization that will set off an AP.
glycine transport inhibitors
When a neurotransmitter is released into the synaptic cleft, transporters on the presynaptic side try to repackage the neurotransmitter. Glycine transport inhibitors prevent this, thus prolonging the inhibitory effect of glycine.
time cells in MEC
When a rat had to do a T maze, with a delay zone that was a treadmill, found that there were neurons that coded for the amount of time spent on the treadmill.
theta phase precession
When an animal runs along a linear track, place field spiking will change such that spikes will occur a little earlier in the theta oscillation, until halfway through when the spike will occur at the trough of the theta oscillation, but the procession will increase until it gets back to the peak.
Does SCS activate a descending modulatory mechanism?
When an experiment was done, the amount of analgesia when stimulating away from the site was less compared to stimulating above the site of analgesia. This indicates that the target of analgesia in SNS must be in the dorsal horn at the segment being stimulated.
How is cerebellar blood flow affected by an increasing neural response?
When climbing fibres are stimulated, a linear relationship is seen between underlying neural spike activity (sum of LFPs) and % CBF. In contrast, when parallel fibres are stimulated, there is a sigmoidal relationship between underlying neural spike activity (sum of LFPs) and % CBF.
medial septum inactivation and grid cell recordings
When muscimol (a GABA agonist) is injected into the medial septum, can see that grid cells reversibly stop working (work again 4-5 hours later, once muscimol has worn off).
So, how does cochlear amplification work?
When outer hair cells change length, their motion increases the motion of the basilar membrane, thus further amplifying the receptor potentials of both inner and outer hair cells.
Rat experiment in the dark where the animal must leave a refuge, retrieve a food pellet, and return to its refuge
When taking recordings from head direction cells, it was found that a shift in the head direction system correlates with an error in behaviour, showing that head direction cells actually do act like an internal compass.
What happens at the level of the hair cells?
When the basilar membrane is excited due to fluid in the cochlea, a shearing force causes the stimulation of hair cells. There is a difference in pivot point of basilar vs. sectoral membranes such that an upward deflection of the basilar membrane causes excitation and a downward deflection of the basilar membrane causes inhibition.
What causes excitation and inhibition in the cochlea?
When the hair cells move up, there is excitation and when the hair cells move down, there is inhibition.
medial septum inactivation and hippocampal theta oscillations
When the medial septum is inactivated, theta oscillations are wiped out, telling us that the medial septum is a pacemaker for coordinating the temporal aspect of the hippocampus.
hippocampal place cells signal memory by changing their firing rates
When there's a T maze for rats, change the input slightly, driving firing rate.
How does oxygen consumption affect BOLD signal?
When there's an increase in CMRO2, there's an increase in deoxy-HB, which causes more disruption in the homogeneity of the magnetic field, decreasing the BOLD signal.
How does modifying efferent activity affect afferent nerve fibres in the auditory system?
When you stimulate OC medial neurons that act on outer hair cells, there's a shift in the firing rate vs. sound intensity curve of afferents, meaning that the sound has to be played louder to get a response. This tells us that by inhibiting outer hair cells, we need to play a sound 40dB louder to get a response.
microstimulation of IT
When you stimulate an area of neurons that's selective for faces, monkeys way more often state that they recognize a face in the image they're looking at, even if it's all noise.
The strength of a sensory response depends on what?
Where in the receptive field you stimulate and with what intensity
What is the dorsal visual pathway?
Where pathway
How does cerebral blood volume affect BOLD signal?
With an increase in CBV comes an increase in deoxy-HB content, which causes more disruption of the homogeneity of the magnetic, decreasing the BOLD signal.
So, how is an increase in neural activity encoded in terms of BOLD signal?
With an increase in neural activity comes an increase in O2 consumption, but there's increased blood flow, which overcompensates for the increased deoxy-HB due to increase CMRO2. There is twice the increase in arterial blood flow for an increase in neural activity, meaning that oxy-HB increases, washing out deoxyHB, increasing the homogeneity of the magnetic field, and thus increasing the signal measured
place coding at high frequencies for quiet sounds
With quieter sounds come fewer spikes fired
What happens to working memory as a result of acute and chronic psychological stress?
Working memory is impaired
Is there something about resting states at the meso scale that is beyond random fluctuations?
Yes! It can be seen when recording from V2, for example, that the functional architecture of resting states matches the functional architecture or response maps more than would be random. Cortical activity patterns that are similar to the pattern of response to oriented gratings occur spontaneously 15-20% of the time, more than is expected by chance.
Is the interaction between the dorsal tegmental nucleus and the lateral mammilary nucleus important?
Yes, because a lesion of either affects head direction cells downstream.
Is there a difference between the medial and lateral entorhinal input to the hippocampus, in terms of place code?
Yes, there are beautiful place cells in MEC, but not nice ones in LEC.
Are grid cells a defined cell type?
Yes, they are a defined cell type in the MEC. A grid cell will always be a grid cell, even if put in a new environment.
Do sharp-wave ripple events propagate at all?
Yes, they propagate throughout the hippocampal formation. They are very strong in CA1 in particular. When there's ripple activity, you can see it outside the hippocampus.
What does the reactivation of place cells during sharp-wave ripples teach us?
You are constantly replaying trajectories you have during the day.
What can we figure out from Weber's law?
You become less able to detect the same magnitude of change in a stimulus when the stimulus becomes greater.
complex stimuli selectivity in IT
You get face selectivity in IT as there are some neurons in IT that respond to specific conjunctions of features. IT neurons can be tuned to different views of different faces, as well as other objects and body parts.
cochlea
a coiled, bony, fluid-filled tube in the inner ear through which sound (pressure) waves trigger nerve impulses
What is required for the perception of biological motion?
a conjunction of form and motion
distributed representation to encode spatial position
a downstream neuron would have to know which pyramidal cells are firing and which aren't in different locations (can't figure out location if you only know info from one cell)
How are local field potentials obtained (below 150Hz)?
a filter cut-off is used
How is multi-unit activity obtained (above 400Hz)?
a filter cut-off is used that separates slow waves from high frequency waves
What is the Hermann grid illusion?
a grid of black squares with white borders separating them, but if you look at it, the interstices of the grid don't appear as white as elsewhere outside the grid
What happens to an on centre / off surround achromatic retinal ganglion cell when presented with a stimulus that has a light centre and a dark surround?
a huge increase in action potentials
extracellular recording
a method of taking cell measurements non-invasively, often done through a Patch-clamp experiment that measures the potential in the cell with reference to the potential outside the cell
Eustachian tube
a narrow tube between the middle ear and the throat that serves to equalize pressure on both sides of the eardrum and is usually closed
So, neurally, what is an efference copy, based on EOD experiment in electric fish?
a negative image of predicted sensory input, therefore changes in the reafferent stimulus cause changes in the efference copy
default mode network
a set of brain regions that are more hemodynamically active during rest than during tasks, forming a resting state network
local field potentials
a single event has a duration of approximately 10-100ms with a radius of 1-2mm that represents population synaptic potentials, voltage-gated membrane oscillations, and the input of a given cortical area as well as its local intra-cortical processing (including the activity of excitatory and inhibitory neurons)
Multi-unit activity
a single event has a duration of approximately 1ms with a radius of 100-200 microns that represents mainly the activity of projection neurons that form the output of a cortical area
axo-axonic synapse
a synapse at which a presynaptic axon terminal synapses onto the axon terminal of another neuron - occurs with the connection between PV neurons and PKCgamma neurons
language
a system of visual or auditory symbols and the rules used to manipulate them
central auditory processing disorder
a variety of disorders that affect the processing of auditory info, leading to difficulties recognizing and interpreting speech or localizing sound, with unknown and varied causes
PET scan
a visual display of brain activity that detects where a radioactive form of glucose goes while the brain performs a given task (detects changes in blood flow)
spatial frequency sensitivity
a way of describing an observer's ability to see gratings of different spatial frequencies
temporal frequency sensitivity
a way of describing an observer's ability to see gratings that flicker at different rates
homeostasis
ability to maintain a relatively stable internal environment with changing external conditions
How much taller are hair bundles at the apex compared to at the base of the cochlea?
about 2x taller in humans
How large is the sensitivity range of an afferent contacting an inner hair cell?
about 30dB
Working memory as a child is linked to what?
academic success
2 types of retinal ganglion cells
achromatic and colour-opponent
antidepressant drugs
act on monaminergic systems (serotonin, norepinephrine, dopamine) as these transmitters have widespread connectivity in the CNS and produce coordinated responses for arousal, attention, vigilance, motivation, and other cognitive and emotional states
Efferents from the medial olivary complex in the brainstem
act on outer hair cells, affecting their ability to change length and affect cochlear amplification
meatus
acts as a resonator, allowing through frequencies between 2,000 and 5,000 Hz
lesions of the left hippocampus
affect memory for words, objects, or people
lesions of the right hippocampus
affect spatial memory
What happens to afferent responses in response to loud, sustained sounds?
afferents adapt
Where do nerve fibres synapse on a hair cell?
afferents and efferents synapse on the basolateral surface
pinwheel model of the visual cortex
all preferred orientations converge at a point and going out from that point radially, there's a whole circle of the preferred orientation changing smoothly, showing that nearby neurons prefer the same orientation and that transitions smoothly to nearby neurons
sympathetic nervous system
all preganglionic fibres come out of the spinal cord and contact postganglionic fibres at ganglia near the spinal cord and then postganglioninc fibres are super long to reach target tissues
spatial filter
allows certain frequencies to pass and rejects others
binaural processing
allows us to combine info from both ears, localizes sounds in noisy situations
Advantage to high pass filtering when doing extracellular recordings from CA1
allows you to see spikes from individual neurons more clearly
high pass filtering
amplifies or deletes all but the high frequencies, since spikes are at higher frequencies, while local field potential is primarily at low frequencies
What do hearing aids do?
amplify sound
loudness
amplitude (force / surface area)
McGurk effect
an error in perception that occurs when we misperceive sounds because the audio and visual parts of the speech are mismatched.
sensitization
an increase in behavioral response after exposure to a stimulus
critical period
an optimal period shortly after birth when an organism's exposure to certain stimuli or experiences produces proper development
bait shyness
an unwillingness or hesitation on the part of animals to eat a particular food
What counts as macroscopic scale in the nervous system?
anatomically segregated brain regions and inter-regional pathways
electrolocation with electric fish
animal emits a field around its body, which will be distorted by objects, so that the animal can sense where things are
aplysia response to repeated stimulation
animal will display habituation if repeatedly stimulated at the siphon unless a noxious stimulus is applied, at which point tactile stimulation of the siphon will cause a greater behavioural response
What establishes the midbrain / hindbrain boundary?
anteroposterior patterning with wnt family proteins, producing differences in Otx2 and Gbx2 factor transcription
anti-Hebbian STDP and reafferent input
anti-Hebbian STDP underlies the adaptive cancellation of reafferent input
treatments for ear infections
antibiotics and / or a window being made in the tympanic membrane to allow for the re-equilibration of pressure
Fourier transforms
any signal can be written as the sum of sinusoidal functions of different frequencies and amplitudes
At which part of the hair cell are the stereocilia?
apical part
Stereocilia of the hair cells
are filled with cross-linked actin filaments and have a staircase arrangement with a tapered base, allowing the hair bundle to pivot in response to mechanical forces
selectivity for binocular disparity in the visual cortex
area V1 concerns itself with depth as defined by disparity
selectivity for motion direction in MT
area has a columnar orientation similar to the one found in V1, where each cell in a column prefers the same motion orientation and nearby columns change gradually for a smooth change
place field in hippocampal spatial memory
area of space that the animal must be located in in order to elicit firing from a given pyramidal cell
subiculum
area of the hippocampus that receives info from the entorhinal cortex and CA1 and feeds back to the entorhinal cortex
entorhinal cortex
area of the hippocampus through which information enters and leaves (feeds into parahippocampal cortex, perrihinal cortex, dentate gyrus, CA3, CA1, and subiculum)
linguistic specialization
arises around year 1, means that infants learn which phonetic units convey meaning in their language (understand around 50 words and produce speech)
How many cells are in the subiculum in rats?
around 180 thousand cells
How many cells are in the 2nd layer of the entorhinal cortex in rats?
around 200 thousand cells, 20% of which are interneurons
perforant path projection to the dentate gyrus in rats
around 4500 spines per granule cell (75% from EC) and one EC cell makes about 18,000 synapses with granule cells in the DG
specific arousal
arousal specific to a context and system (like sexual arousal)
How can one describe the motion along the basilar membrane?
as a travelling wave, 150nm in height
sensitivity curve for brightness contrast
as contrast increases down the y-axis and spatial frequency increases up the x-axis, we see a curve showing where a subject would be able to accurately distinguish brightness
spatial working memory in rodents
as the animal's location is changing, different CA1 pyramidal cells are firing whose place fields encompass that particular location, giving the animal info as to its location in space
operant conditioning
associating a specific behaviour with the consequences of that behaviour (must be a predictive relationship between a stimulus and behaviour)
mechanism for inducing postsynaptic LTD
assuming calcium can flow into the postsynaptic membrane (everything is all good with the NMDA receptors etc), calcium interacts with protein phosphatases, increasing the rate of internalization of AMPA receptors
mechanism for inducing postsynaptic LTP
assuming calcium can flow into the postsynaptic membrane (everything is all good with the NMDA receptors etc), calcium sets off a protein kinase cascade, leading to the insertion of AMPA receptors in the membrane, increasing the postsynaptic current, increasing EPSP amplitude
NMDA receptors
at rest, magnesium ions plug the pore, which is released when the membrane is depolarized, allowing sodium and calcium to enter and potassium to exit in the presence of glutamate (excitatory)
associative plasticity
at the postsynaptic level
non-associative plasticity
at the presynaptic level
kinocilium
at the tallest end of the stereocilia, atrophies as the animal matures, doesn't play a role n hearing
Physiologically, how are motivational states regulated?
autonomically and endocrinologically
optic nerve
axons of the ganglion cells leading from the retina to the brain, resulting in a blind spot
Where does layer 6 of V1 project?
back to the LGN
Where does layer 5 of V1 project?
back to the superior colliculus (sub cortex)
cerebellum functions
balance coordinating movement timing of movement timing of discontinuous movements motor learning
medullar CNS division
basic vital faculties
Why interaural time difference sound localization work only at low frequencies?
because for low frequency sounds with long wavefronts, you can pick out the phase to know which ear a sound is arriving at first, but for higher frequency sounds with a short wavelength, you can't detect phase info
Why do afferents connecting to inner hair cells have different sensitivity ranges?
because of properties of the hair cell-to-afferent synapse and the properties of the afferents themselves
RUNX3 / trkC neurons
become mechanoreceptors and proprioceptors
RUNX1 / trkA neurons
become nociceptors
microsimulation of MT direction columns
biases perception, as seen in the variable coherence dot fields experiment such that monkeys now exhibited a bias towards motion in one direction, regardless of which direction the dots were actually moving
microsimulation of MST column
biases the perception of heading in a particular direction
advancing age and presbycusis
bilateral hearing loss that increases with increasing age, largely confined to frequencies >1,000Hz
practice phase in zebra finches
bird practices its song, starts vocalizing and gets feedback on performance
error-driven model for learning and maintaining zebra finch song
bird stores model of the song bird sings and attempts to reproduce the model song feedback happens over and over during the practice phase
APV
blocks NMDA receptors
short term cues that control food intake
blood glucose and intestinal hormones (cholecystokinin) regulate size of individual meals
types of cones
blue, green, and red - sensitive to different wavelengths
emotion
bodily state, automatic, largely unconscious behavioural and cognitive responses mediated by peripheral, autonomic, endocrine, and skeletomotor responses (involves subcortical structures)
Are parvocellular ganglion cells achromatic or colour-coded?
both
what determines place fields?
both external and self-motion cues
nucleus of the solitary tract
brainstem region that integrates visceral sensory inputs and autonomic outputs and projects to higher brain centres involved in homeostasis
brainstem regions and ANS
brainstem regions mediate direct autonomic reflexes and also project to higher brain areas (like the hypothalamus), which regulate more complex autonomic responses
uncus
bulbus structure under the frontal lobe that comprises the hippocampus, amygdala, and entorhinal cortex
How is loudness coded at the afferent level?
by increasing the firing rate of one afferent and by recruiting additional afferents
How is the size of an object typically described?
by the size of the angle it covers on the retina in degrees
EGTA
calcium chelator
determining if calcium will set off phosphorylation or dephosphorylation
calcium has a higher affinity for phosphatases than protein kinases, so that's why if we have just a little bit of calcium, then these will win and we get net depression in EPSP amplitude, but if there's lots of calcium, kinases will win and we'll get LTP
Macaque cortex
called the middle fat patch, in the floor of the superior temporal sulcus, seems to respond strongly and selectively to faces
interneuron
can be excitatory or inhibitory, when the cell body and axon stay within the dorsal horn
lesions of posterior parietal cortex
can cause the loss of semantics (can't understand the naming of words) or associative agnosia (where patients can draw simple things, but can't name them
extracellular recording of AP in awake, behaving rodents (unit recording)
can insert tetrodes in CA1
lesion to CA1 of the hippocampus
can no longer form long-term memories
Wernicke's aphasia
can produce effortless and melodic speech at a normal rate, but often unintelligible and have frequent errors in word retrieval and difficulty comprehending speech
lesions to Macaque cortex
can't detect faces, despite a functional visual system otherwise
What is the origin of the BOLD signal, more specifically than just blood vessels?
capillaries, venues, and veins, because there is almost no deoxy-HB in arteries and arterioles
Easier way to solve the aperture problem
cells that respond to curves or angles
horizontal connections in V1
cells with similar orientation or colour preferences are connected anatomically in the upper layers of V1 (often connected in an inhibitory way), where horizontal connections often span several millimetres and link hypercolumns corresponding to different parts of visual space
primary sulci and gyri of the brain
central sulcus, lateral sulcus, cingulate sulcus, parietal occipital sulcus, calcacarine sulcus, cingulate gyrus, corpus callosum
superior colliculus receptive fields
centre / surround organization with big receptive fields and input coming mainly from magnocellular retinal ganglion cells, so good at measuring things moving or flickering
fovea
centre of the retina, at which images have the highest resolution due to the highest concentration of photoreceptors and a peak in cone concentration
development of the forebrain
cerebral hemispheres swell and envelop the diencephalon olfactory bulbs sprout off each telencephalic vesicle
GABAergic neuron types projection patterns
chandelier cells (terminate on axons of layer II and III pyramidal neurons) large / small basket cells (terminate on cell bodies of pyramidal neurons) double bouquet and neurogliaform cells (latter associated with axosomatic synapses on spiny non-pyramidal neurons
symptoms of depression
change in appetite or sleep patterns, feelings of guilt or worthlessness, fatigue, and reduced ability to concentrate
cataract
changes in the lens colour
PV protein role
chelates calcium because if too much calcium builds up, potassium channels are opened, which hyperpolarizes the neurons, silencing PV AP
What fine tunes the innervation of sensory neurons?
chemo attractants and chemo repellants
"high road to emotion"
circuit that goes through neocortical processing - thought to be unique to high animal species cause it lets us more cognitively assess emotions and decide what our response will be
"low road to emotion"
circuit that goes through only subneocortical processing
associative implicit learning
classical and operant conditioning, constrained by biological factors
How are local field potentials classified?
classified to frequency bands used in EEG, those are delta, theta, alpha, beta, and gamma
human frequency sensitivity
closely correlates with what we saw with contrast sensitivity and is ultimately limited by simple cells in V1
How is timing info about hearing preserved in the brain?
cochlear nucleus spherical bushy cells preserve timing info and project to the superior olivary nucleus, where maps of location of sounds in space are mapped
What happens in the external ear?
collection of mechanical energy (sound waves)
What are thin stripes in V2 for?
colour
IT organization
columnar clustering organization of preference for complex stimuli
organization of MST
columnar, but the clustering is based on selectivity for complex motion stimuli
global aphasia
combination of Broca, Wernicke, and regions associated with conduction aphasias
How can we model complex cells of visual cortex based on simple cells?
complex cell could be constructed by adding the outputs of simple cells with the same orientation, but receptive fields at different positions, so that you always get a response as long as the orientation is correct (the next simple cell receptive field could have on centre, followed by one with an off centre, etc.)
addiction
compulsive drug use despite significant negative consequences
Broca's aphasia
condition in which you can produce speech with grammatical impairments like slow speech, articulation, and intonation impaired and have an inability to repeat and understand grammatically complex sentences
rat task for classical conditioning
conditional stimulus = tone unconditional stimulus = foot shock The foot shock elicits freezing. The tone was paired with a foot shock until freezing was elicited after just a tone (conditional response).
fimbria / fornix to subcortical areas
connect to the septum, this pathway dies off in Alzheimer's and epilepsy
ventromedial prefrontal cortex
connected to the amygdala and the hypothalamus and is important for connecting the physiological states of the body to conscious emotions
Otto Loewi experiment
connected two heart chambers by making a pump between the two and when the fluid that goes around heart 1 (which is stimulated to slow HR) is put around heart 2, heart 2 also showed a response, slowing HR
Schaffer collateral pathway
connection between CA3 and CA1 pyramidal cells in the hippocampus
mossy fibre pathway
connection between the granule cells of the dentate gyrus and the pyramidal cells of CA3 in the hippocampus
What counts as meso-scopic scale in the nervous system?
connections within and between cortical columns or other types of local cell assemblies
simple cell receptive field
constructed from the outputs of LGN cells that have receptive fields shifted along a line, with on centre and off centre cells forming parallel rows
Efferents from the lateral olivary complex in the brainstem
contact afferent nerve fibres in an inhibitory way, so if they were to act on type I auditory fibres, would reduce the output of the inner hair cells to the CNS
What is the main function of V3?
contains columns concerned with binocular disparity
Which abilities are not affected by V2 lesions?
contrast detection, orientation, colour, or motion direction
mCit virus
control fluorescent virus that can be injected when doing hM3D and hM4D experiments
the role of omega in a sine wave describing visual brightness
controls the spatial frequency
Why do we miss info in fine scale in space and time with fMRI alone?
conventional fMRI voxel is 2 x 2 x 2 mm and sampling rate is one volume / 1-2s, with sluggish BOLD signal, so we can't see when exactly specifically neurons are acting
transduction
conversion of one form of energy to another, in the nervous system, involves the opening and closing of ion channels based on different stimuli
differences between rat vs. human brain
convolutions (sulci and gyri) forebrain organization (small olfactory bulbs for humans and cerebral hemispheres that arc) brainstem orientation
The nucleus accumbens is made up of which two parts?
core and shell
normal audibility curve
curve that shows that sensitivity is not the same at all frequencies and damage can result before pain
conduction aphasia
damage to the left superior and supra marginal gyri, a person can comprehend simple sentences, but cannot repeat sentences verbatim
sensorineural hearing loss
damage to the organ of Corti or the 8th nerve, caused by persistent loud noises, toxic drugs like stretomycin, old age, tumours of the 8th nerve or infections
BrainMap
database on which brain coordinates are activated by specific tasks
Did Hellen Keller think it was worse to be blind or deaf and why?
deaf because it was more socially isolating
congenital deafness
deafness from birth that occurs about 0.1% of the time and is genetic about half the time
What happens if you reduce outer hair cell function through efferent activation, drugs, or ablation?
decrease in cochlear sensitivity and frequency discrimination and a lack of otoacoustic emissions
Weber's law
deltaS = K*S where K is a constant deltaS represents the minimal difference in strength between a stimulus S and a second stimulus
just noticeable difference
deltaS in Weber's law
language-specific speech perception
depends on which language or languages the baby was exposed to, starts around 6 months
power spectrum
described the frequency components of an image, as distance from the origin corresponds to spatial frequency and angle in the plane corresponds to the orientation of the sine wave (doesn't tell about phase though)
utricle and saccule
detect linear acceleration
strength of classical conditioning
determined by how associated the conditional and unconditional stimulus are
spatial resolution of a sensory system
determined by the density of receptors and the size of receptive fields
empiricism
developed by Skinner, the idea that language is learned
d' in signal detection theory
difference in the means of the desired stimulus and the actual stimulus (m) / spread (s) (for example, two curves, one representing a 6g marble and the other representing an 8g marble, while trying to detect 6g marbles)
optic flow
direction of visual motion at different locations, relating to self-motion
ECT
disrupts recent memories by giving pulses to the temporal lobe, inducing epileptic seizures in that area
lesions in area X of songbirds
disrupts song learning in juveniles, but have no effect on adults
How can we try to find out if spikes or synaptic activity is reflected by the BOLD signal?
dissociate spikes and synaptic activity
remapping of place field
does not occur when landmark's position is rotated with the animal's knowledge (translated)
lesion of the amygdala with respect to memory
doesn't impair explicit memory
horizontal brain slices
dorsal - ventral
Which brain location was observed to study spatial working memory?
dorsolateral prefrontal cortex showed neural responses when monkeys were using their working memory
variable coherence dot fields monkey experiment
dots can move with different levels of coherence and monkeys were asked to indicate the direction of dot motion by making eye movements to the right or left
nonassociative implicit learning
due to the properties of a single stimulation (habituation and sensitization)
blindsight
due to the superior colliculus, a phenomenon activated by large stimuli usually of low spatial frequency or high temporal frequency, wherein a subject can "see" what's there without perceiving that he or she is seeing (little sensitivity to colour)
When are sharp-wave ripple events most prevalent?
during slow wave sleep and resting
6 layers of the LGN
each layer retains info about which eye the info is coming from 1. contra 2. ipsi 3. ipsi 4. contra 5. ipsi 6. contra
apex of the basilar membrane
elastic and wide, responds to low frequencies (20Hz), furthest away from the oval window
electric fish
emits electric fields through an electric organ in their tail has highest cerebellum to brain ratio of all animals
In terms of language, what is the right hemisphere used for?
emotional prosody like vocal emotion cues and pragmatics of language
processing of angles in V2
encode angles defined by two orientations, which helps with the perception of shape and depth
What does nicotine do to make it addictive?
enhances the release of dopamine by acting on presynaptic cholinergic receptors
nociceptors' connection to the spinal cord
enter from the side (lissauer track) into the superficial layers
Hyperphagia
excessive eating, can result from destruction of the ventromedial nucleus of the hypothalamus
PKCgamma neuron
excitatory interneuron that can activate projection neuron
double-opponent blob cells in V1
excited by one colour in the centre, but inhibited by its opponent colour in the centre and excited by that opponent colour in the surround, but inhibited by the original colour in the surround (like how achromatic retinal ganglion cells worked)
vascular volume receptors
exist in the right atrium, great veins, aortic and carotid sinus (kidneys release renin in response to low vascular volume)
exafference
externally generated
characteristics of explicit memory
facts, highly flexible so that we can integrate info, hippocampus is critical
hyperopic
farsighted: light converges behind the retina
What connections drive fast gamma hippocampal oscillations? (~90Hz)
fast gamma reflects MEC-CA1 synchrony
How does redundancy reduction work?
filter the image in a centre / surround way, eliminating all that is uniform, letting you see where things are changing, showing that correlation falls much more rapidly
What happens when a human in a virtual environment runs along an axis of grid cells?
find that aligned running shows increased neural activity
tip links
fine filamentous link that connects two adjacent stereocilia, allowing for the transfer of info
blobs in V1
form little columns that are only in layers 2 and 3 and care about colour, but not orientation
How do grid cells relate to the treadmill T wave task?
found that grid cells also code for distance and time
London taxi driver experiment
found that taxi drivers had hippocampi of the same total volume as others, but larger posterior hippocampi and smaller anterior hippocampi (affects both the right and left hippocampus)
synchronization between intracellular cortical recording and recording using voltage-sensitive dyes
found that the two time courses are very similar to each other, indicating a high level of cortical synchronization
difference between grid cells from dorsal to ventral MEC
found that there were small fields with small spaced in between at the dorsal end, while at the ventral end, fields got bigger, and the spaces between them increased
Okay, so now that we can turn off grid cells by inactivating the medial septum and record from place cells, let's do so
found that theta oscillations were reduced when the medial septum was knocked out (as expected), but even without working grid cells, there were immediate place cells formed in novel environments, casing doubt on the fact that place cells receive their input from grid cells
pitch
frequency of sound
Where does the BOLD signal originate?
from cortical blood vessels in pia matter, where blood is brought in and taken out
How can the orientation tuning of a simple cell be predicted?
from its response to small spots of light
brain location of episodic buffer
frontal lobe
4 major lobes
frontal, parietal, temporal, occipital
What determines the frequency response?
functional anatomy of the ear
pinna
funnels sound waves into the meatus
abdominal ganglion in aplysia
ganglia near the abdomen
filter out temporal redundancy
ganglion cells filter out tings that are constant against time, causing correlation to drop off very sharply
error signal (ANS)
generated by the integrator when the value of a controlled variable does not match the set point
trunk neural crest
generates sensory, sympathetic, and enteric neurons of the PNS
effect of 10mM EGTA on plasticity with high frequency tetanus
get LTD
effect of 15uM APV on plasticity with high frequency tetanus
get LTD
effect of 3Hz tetanus on Schaffer collaterals
get LTD, weakening of EPSP amplitude
effect of 0.5mM EGTA on plasticity with high frequency tetanus
get LTP
effect of 0uM APV on plasticity with high frequency tetanus
get LTP (plasticity requires NMDA receptors)
effects of 50Hz tetanus on Schaffer collaterals
get LTP, strengthening of EPSP amplitude
What do you get when you filter out everything except low spatial frequencies?
get a blurry image with a lack of detail
What do you get when you filter out everything except medium spatial frequencies?
get an image with some detail, but still quite blurry
What do you get when you filter out everything except high spatial frequencies?
get very sharp image
suprachiasmatic nucleus
gets info from the eye
co-activation of parallel and climbing fibre input in the cerebellum
gives rise to LTD
what does the tail shock do on a molecular level?
gives synapse to a modulatory interneuron, releasing a modulator
AMPA receptors
glutamate receptor that conducts sodium
mechanosensitive neurons' connection to the spinal cord
go to the dorsal column before entering the spinal cord and go down to lamina 3 - 5
Layer III from the entorhinal cortex
goes to area CA1 and the subiculum in the hippocampus
Layer II from the entorhinal cortex
goes to the dentate gyrus and area CA3 in the hippocampus
cells in the dentate gyrus
granule cells that send their dendrites straight out
sensitivity axis of hair cells
hair cells are only activated when pushed in the correct direction (depolarization if towards the tall edge and hyper polarization if pushed towards the short edge)
shell of the nucleus accumbens
has strong connections to the limbic system and the hypothalamus (very sensitive to addictive drugs)
conjunctive cell
head direction selective grid cell in the entorhinal cortex that only fires when the head is in the right direction and within the grid field
What does the posterior hypothalamus have to do with temperature regulation?
heat conservation
What does the anterior hypothalamus have to do with temperature regulation?
heat dissipation
Small receptive field correlates with what?
high acuity
parvocellular ganglion cells
high spatial resolution, low temporal resolution, colour sensitive, common in the fovea, small receptive fields, concerned with form
rods
highly light-sensitive (threshold of just 1 photon), low temporal resolution, low spatial resolution, colour-blind, common in peripheral vision, saturate in brightness (so can't discriminate between levels of brightness)
What is the basis of endstopping?
horizontal connections in layers 2 and 3 of V1, in which there are cells that prefer the same orientation
pragmatics of language
how context contributes to meaning / social meaning
neurovascular coupling
how the dilation of arteries causing an increase in blood flow relates to neural activity, allowing the MRI machine to figure out neural activity
mean luminance
ideally falls right in the middle of the light intensity around you, once you have adapted to light
anti-Hebbian STDP
if dendritic spike occurs after EPSP, we get depression, whereas if dendritic spike occurs before EPSP, we get potentiation
Hebb's postulate
if we have postsynaptic neuron B and presynaptic neuron A, then when A fires, B also fires, leading to potentiation
songbird song orientation
if we reverse the order in which the song is presented, it will sometimes be sung in reverse order
optical imaging of intrinsic signals
imaging method that relies on the light absorption properties of deoxy-HB and oxy-HB, creating a signal if the ration of oxy-HB / deoxy-HB changes
How quickly are grid cells formed in new environments?
immediately - even in the first minute, the animal starts forming fields that become stable over time
MT lesions
impair the ability to see motion in noisy stimuli (monkeys need 100% coherence to even have any close idea)
Effects of magnocellular lesions in the LGN
impair the perception of fast-moving stimuli, but no effect on acuity or colour discrimination
2 main memory types
implicit (non-declarative) and explicit (declarative)
dopamine
important for motivation, learning, and action
semi-circular canals
important for regulating rotation
What improves second language learning?
improved by conditions similar to early learning, like long periods of listening in a social context, the use of auditory and visual info, and the exposure to simplified or exaggerated speech
unconditional stimulus
in classical conditioning, a stimulus that elicits an unlearned, naturally occurring response
conditional response
in classical conditioning, the learned response to a previously neutral (but now conditioned) stimulus
extinction
in classical conditioning, the process over time of na animal losing the association between stimuli
region specific song motifs
in different regions, there are different song motifs, imitating accents in human language
angular velocity cells
in lateral mammilary nucleus, dorsal tegmental nucleus, lateral habenula, nucleus prepositus, and medial vestibular nucleus
song system bird brain anatomy
in the hemispheric forebrain, auditory input comes into HVC, which projects onto RA and area X, which projects to DLM LMAN projects to area X and to RA as well RA projects to syrinx, the vocal organ
Broca's area
in the left posterior frontal cortex, may be related to short term memory for language
Where does interaural level difference sound localization take place?
in the lower super olive
Where does interaural time difference sound localization take place?
in the medial superior olive
endolymph
in the scala media, similar to intracellular fluid, has a high K+ concentration, creating a standing potential, produced by cells in the stria vascularis
perilymph
in the scala vestibuli and tympani, similar to extracellular fluid, has a high Na+ concentration
habituation and synaptic connections in aplysia
in the short term, habituation is caused by a decrease in vesicle number, while in the long term, the number of synapses is decreased
aphasia
inability to produce language
posterior parietal cortex lesion leading to difficulty reaching for and grabbing objects (optic ataxia)
inaccurate shaping of objects and misorientation of the hand
hippocampal formation
includes CA1-3, dentate gyrus, entorhinal cortex, subiculum, and pre and post parasubiculum
What do heroin and mu opiod agonist do to make them addictive?
increase dopamine by inhibiting GABA-neurons that suppress dopaminergic neurons in the ventral segmental area
What do cocaine and amphetamines do to make them addictive?
increase dopamine in the nucleus accumbens by blocking the dopamine transporter
year 3 language specialization
infants at this age know 3000 words and produce adult-like sentences
language development
infants initially exhibit universal patterns of speech perception and production, can discriminate sounds from all languages, start babbling, first speak around 1 year
universal speech production
infants produce non-speech sounds until 3 months, then vowels, then canonical babbling around 7 months, lasts until around 10 months
What kind of input do grid cells in the dorsal MEC receive?
info about distance (generated from speed cells) and head direction
What information do simple cells in the visual cortex convey?
info about orientation and local contrast
What information do complex cells in the visual cortex convey?
info about orientation, but not about local contrast
pons CNS division
info from the cerebrum to the midbrain
simple cell model to explain how V1 can select for orientation
information about orientation emerges from the spatial arrangement of on and off centre LGN inputs since each V1 cell gets input from multiple LGN cells
What happens to an on centre / off surround achromatic retinal ganglion cell when presented with a stimulus that has a dark centre and a light surround?
inhibition of action potentials
What is so bad about chronic elevated cortisol levels?
inhibits the immune system and can affect the ability of new cells to be generated and cause the death of existing neurons - damages the hippocampus (which usually acts as a negative feedback on HPA) (depressed patients are also seen to have smaller hippocampi, but whether the is the cause of depression or a side effect is unknown)
effect of 10Hz tetanus on Schaffer collaterals
initial depression, but EPSP quickly returns to its control values
conditional stimulus
initially neutral stimulus that comes to elicit a response due to association with an unconditioned stimulus
Perforant path
inputs coming into the hippocampus via the entorhinal cortex
How do LGN inputs feed into V1 in cases of motion in the non-preferred direction?
inputs from the LGN arrive asynchronously, leading to a small output from the simple cell
multimodal areas
integrate information from multiple different sources and carry out many higher mental functions
How does the hypothalamus control drinking behaviour?
integrates hormonal and osmotic cues sensing cell volume and state of extracellular space
conduction deafness
interference with sound conduction of the external or middle ear, caused by wax accumulation, otitis media (infection) or otosclerosis
3 things needed for spatial navigation
internal compass external landmarks spatial map
ventral visual pathway
involved in knowing what an object is and assigning emotional significance
dorsal visual pathway
involved in knowing where an object is located in space
model for endstopping in V1
involves the inhibition from neighbouring neurons, ie. if a bar crosses into the receptive fields of neighbouring neurons, those neurons can have an inhibitory effect, negative the excitatory effect of the bar being in the right orientation and direction for the middle neuron
Why do grid cells show hexagonal organization?
it's the best organization to cover the most area in as little space as possible (think covering a table in pennies)
amygdala
key interface between visceral, autonomic responses, and cognitive feelings
deafen songbird song
lack of auditory feedback gives rise to a song that's not like that of the control
aphagia
lack of eating, can be the result of bilateral lesions of the lateral hypothalamus
characteristics of human speech development
language develops spontaneously exposure to vocalizations early in development critical for vocal learning period of practice gradually leading to a match between model and imitation after learning, loss of feedback causes gradual deterioration social interactions influence development of vocal learning
enteric nervous system
largely autonomous, contains 100 million neurons, has two ganglia (myenteric and submucosal plexuses), targets smooth muscle and glands
characteristics of V1 neurons
larger receptive fields than LGN neurons tuned to more sophisticated stimulus properties than LGN neurons represent every aspect of vision (shape, motion, colour, depth, etc.) are organized into columns
lesioning areas 33 or 34 of the brain
last resort treatment for depression
Where do outputs from the distal subregion of CA1 go?
lateral entorhinal cortex
spatial information processing areas
lateral intraparietal cortex, ventral intraparietal cortex, and medial intraparietal cortex
Which layers of the LGN contain parvocellular cells?
layer 3-6
divisions of layer 4C of the visual cortex
layer 4Calpha all about magnocellular cells layer 4Cbeta all about parvocellular cells
In which layers are complex cells found in V1?
layers 2 and 3
layer 4 divisions in the visual cortex
layers 4A, 4B, and 4C
lesions of the occipital cortex
leads to apperceptive agnosia, where a person can name simple objects, but can't draw them
chronic stress response
leads to longer term changes in the brain, which correlate with depression
lesion in the optic chiasm
leads to loss of the opposite visual fields (loss of left visual field in the left eye and the right visual field in the right eye)
lesion in the optic tract
leads to loss of vision in the visual field opposite to which side of the brain you lesion
lesion to the optic nerve
leads to monocular blindness
lesions of the frontal cortex with respect to memory
leads to source amnesia, where all long-term memories are intact, with no recollection of how that info was acquired
What form of language development occurs around 6-9 months?
learn global sound patterns, prosodic cues
bird exposed to multiple songs in a randomized order
learns to sing a composite copy of songs 1 and 2, so song learning is creative
Language is dominated by which hemisphere?
left
Wernicke's area
left posterior and middle temporal cortex
brain location of phonological loop
left temporal lobe
cingulate cortex and ventral frontal lobe and emotion
lesions of the cingulate cortex and ventral frontal lobe result in the disinhibition of inappropriate behaviour
cones
less light-sensitive (threshold of 100 photons), saturate only in very intense light, high temporal resolution, high spatial resolution, chromatic, common in foveal vision
Why is Patch-clamp recording useful when studying hair cells?
lets you focus on just the current that flows through hair bundle channels
dorsal and ventral commissures
link hippocampi
How can one obtain optimal working memory?
links to the ability to focus attention on task-relevant information and ignore distractions
zebra finch song learning phases
listening phase practice phase crystallization
aperture problem
local measurements of edge motion are 1D, so V1 neurons only see the component of motion perpendicular to the orientation of an edge, meaning that when a moving object is moving through a small receptive field, it is very possible to misattribute the direction that it's going
layers II and III of the neocortex
local projections to cortical neutrons within the same area
grid cell in the entorhinal cortex
looks like a place cell, but has lots of fields organized in equilateral triangles
What is the overall theory of what's occurring in chronic neuropathic pain?
loss of inhibitory function in the dorsal horn
neurotransmitter receptors
lots of different receptor types for any one neurotransmitters
On a hair cell tuning curve, is the spread of movement of the basilar membrane wider at low or high frequencies?
low frequencies
Which frequencies dominate most images?
low frequencies make up most of the image, while higher frequencies just add little bits of details
magnocellular ganglion cells
low spatial resolution, high temporal resolution, colour-blind, located outside the fovea, large receptive fields, concerned with motion
scala tympani
lower compartments of the cochlea that contains perilymph
effects of parvocellular lesions in the LGN
lowers the acuity (messes with perception of high spatial frequencies), abolishes colour discrimination, and reduces contrast sensitivity to gratings moving at low velocities
What is the general dorsal visual pathway?
magnocellular LGN to V1 to V2 and MT to MST to parietal cortex
servomechanisms
maintain a controlled variable within a certain range though a feedback detector that compares a measure value with a set point
angular bundle fibres from EC
make up the perforant path
consolidation
makes learned info stable for long term storage (involves changes in protein synthesis, synapse weight, gene expression, etc)
3 ossicles
malleus, incus, and stapes
How can V1 cells select for position?
many LGN inputs go to V1 cells, telling about the difference in the stimulus position
What is thought to be associated with Wernicke's area?
may be part of a system that associates speech sounds with concepts
Temporal coding at low frequencies for soft sounds
may only have a couple spikes per peak, but louder sounds will have lots of spikes per peak
So, what is the effect when PV neurons are activated?
mechanical hyposensitivity, but no effect on heat sensitivity
differences between aplysia and human hippocampus
mechanisms for plasticity are on the postsynaptic side in humans and the neuromodulator is dopamine, which activates dopaminergic GPCRs, which activate signalling molecules that can cause the growth or retraction of synaptic connections
What happens with down regulation of RUNX3 around day 14 of embryogenesis?
mechanoreceptors develop
sagittal brain slices
medial - lateral
Where do outputs from the proximal subregion of CA1 go?
medial entorhinal cortex
long term explicit memory brain areas
medial temporal lobe (hippocampus, diencephalon)
myelecephalon
medulla
microelectrodes implanted in the hippocampus
microelectrodes can be implanted to allow for place field measurement
scala media
middle chamber of the cochlea that contains endolymph
What is a strategy for sound localization straight ahead, in terms of elevation?
miniature echoes
intracellular recording
more common in vitro, when an electrode penetrates the cell and measures the difference in potential
parasympathetic nervous system
most outputs come from the brainstem nuclei or the sacral part of the spinal cord and then synapse on ganglia near target tissues
age-related (progressive) hearing loss
mostly due to cochlear damage, though can be due to some genetic factors, can be caused by bacterial meningitis, which kills inner ear cells, can be caused by ototoxic drugs (ahminoglycosides), which kill hair cells, or can be caused by noise (hearing loss relating to noise may be due to a genetic predisposition)
aplysia LTP and LTD mechanisms
mostly presynaptic - reliant on the number of vesicles being exocytosed
translation
motion in one direction, tuned for by MT
How can it be proven that grid cells in MEC are the source of info for hippocampal place cells?
must record in the hippocampus and look at place cells, while turning off grid cells
minor function of MT
nearby columns tend to prefer similar disparities
myopic
nearsighted: light converges ahead of the retina
primary visual cortex V1
necessary for conscious vision and receives input from LGN and projects to extrastriate visual areas
How does homeostatic control of physiological functions work?
negative feedback loops (for example, an excitatory neuron also connects to an inhibitory interneuron which feeds back onto the excitatory neuron to dampen the output)
dependence
negative visceral consequences of withdrawal of the drug due to changes in brain cells and circuits
feature invariance
neural representations become invariant, preserving transformations of behaviourally relevant stimulus features (doesn't matter if size, position, clutter, etc changes)
brain map of personal space
neural representations of the body surface provided by the senses of touch and proprioception
What type of cells are hair cells?
neuroepithelial because they retain epithelial cells characteristics, being that they are connected by tight junctions
suppression columns in the auditory cortex
neurons are excited by unilateral input but inhibited by stimulation of the opposite ear
neuron as a spatial filter
neurons in V1 emphasize some spatial frequencies more than others (cells won't fire when the frequency isn't right)
voluntary motor control (corticospinal pathway)
neurons in layer V of the motor cortex direct projections to neurons in the ventral horn of the spinal cord
dense code
neurons respond differentially to a wide range of stimuli
retinotopic map in V1
neurons that are physically near each other respond to similar parts of visual space
head direction cells
neurons that fire based on which direction an animal is facing
encoding
newly learned info is attended to and processed for the first time (attention leads to our ability to start encoding)
Do head direction cells in the ADN require feedback from the postsubiculum?
no
effect of 20mM EGTA on plasticity with high frequency tetanus
no change in EPSP strength
lesions of the medial temporal lobe with respect to memory
no effect on long-term memory
effect of 100uM APV on plasticity with high frequency tetanus
no plasticity
universal speech perception
no predisposition to a particular sound, ends around 7 months
What was found in the ventral MEC?
no sign of place fields
What is the leading cause of hair cell loss?
noise exposure
What happens with removal of trkA around day 14 of embryogenesis?
non-peptidergic nociceptors develop
depolarizing mechano-sensitive ion channels
non-selective cation ions that allow sodium and calcium in and potassium to flow out
general arousal
nonspecific reactions (like increase HR, increased respiration, etc.)
CA1 pyramidal cell spatial field direction or path selectivity
not dependent on either path or direction
subcortical vision in the LGN
not dependent on the orientation of the stimulus, only requires that a stimulus passes through the visual field
What was found in the dorsal MEC?
not just place cells, but cells that locate many locations of the environment were found in hexagonal organization (grid cells)
autonomic nervous system
not under voluntary control, motor neurons going from the CNS send their outputs to a ganglion that will then send a second fibre onto target tissues (smooth muscle, cardiac muscle, and glands)
What can cause dopamine release?
novel activities, goal meeting, and exercise
place fields and novel objects
novel objects inside the place field lead to remapping, while those outside the place field don't lead to remapping
pleasure centres
nucleus accumbens of the ventral striatum and the ventral segmental area of the midbrain have dopaminergic neurons
long term cues that control food intake
ob gene controls leptin, which suppresses appetite, regulating overall body weight since leptin (released by the stomach) inhibits the release of NPY in the hypothalamus (NPY stimulates feeding behaviour)
brain location of visuospatial sketch pad
occipital lobe
sharp-wave ripple events
occur in non-theta states, when the animal is still
rotations of place field
occur when landmark's position is rotated without the animal's knowledge
language specific speech production
occurs around 10 months old
time scale of light adaptation
occurs over a period of seconds
near binocular disparity
occurs when looking at a point closer than the fixation point, so that the image projects to the right of the fovea in the right eye and to the left of the fovea in the left eye
far binocular disparity
occurs when looking at a point further than the fixation point, so that the image projects to the leftt of the fovea in the right eye and to the right of the fovea in the left eye
cognitive representation of a sensory input modelled as a normal distribution
on the x-axis, cognitive representation of marble weight and probability on the y-axis (the area under the curve represents variability due to noise) (probability of it being cognitively represented as the correct weight is 1 at that exact weight)
perfectly sparse code
one neuron firing for one stimulus
Physiological basis of chronic stress
ongoing release of cortisol
percentage of place sensitive cells in the human hippocampus, as compared to that of a rat
only 24% of human hippocampal cells are place sensitive, while around 80% of rat hippocampal cells are place sensitive
sparse code
only a small fraction of neurons respond to any given stimulus
Are magnocellular ganglion cells achromatic or colour-coded?
only achromatic
non-peptidergic nociceptors
only release glutamate and sense mechanical pain
simple cell as frequency analyzers
optimal stimulus fits the simple cell model, because receptive fields measure sine wave frequencies (bigger receptive fields correspond to lower frequencies)
chunking
organizing items into familiar, manageable units for the purpose of remembering
What are pale stripes in V2 for?
orientation (receive input from upper layers)
What are thick stripes in V2 for?
orientation and direction (receive input from layer 4B)
descending projections in the visual system
originate in deep layers V and VI of cortical areas and project back to layers I, II, and VI
ascending projections in the visual system
originate in layers II and III and project to layer IV in the next cortical level
Which hair cells are most susceptible to being messed with in hearing loss?
outer hair cells, which will mess with cochlear amplification and hearing speech in noisy environments
lamina 2 of the dorsal horn in terms of sensory neurons
outer layer contains peptidergic nociceptors, while the inner layer contains non-peptidergic nociceptors
secondary brain vesicles of the forebrain
paired telencephalic vesicles paired optic vesicles diencephalon
What type of pathway does auditory info take in the brain?
parallel pathways - one stimulus that comes in from an auditory nerve fibre will be sent up in multiple channels to higher brain centres
lateral geniculate nucleus
part of the thalamus that processes visual info
general ventral visual pathway wiring
parvocellular LGN to V1 to V2 and V4 to IT to temporal cortex
What happens when trkA is still present around day 14 of embryogenesis?
peptidergic nociceptors develop
increased delay in mechanical tickling experiment
perception becomes more and more similar to what it would be from an external stimulus
increased directional transformation in mechanical tickling experiment
perception becomes more and more similar to what it would be from an external stimulus
colour-opponent theory
perception of colour is linked to neurons that measure the difference between activity in different cone types
tetanus
periodic train of pulses (defined by period and duration)
brainstem
peripheral area that's a gateway of info exchange between the rest of the brain and bodily functions
What defines sinusoidal functions in 2D?
phase, orientation, frequency, and amplitude
light adaptation chemical explanation
photoreceptor reconstitutes its stock of cGMP, opening the sodium channels and restoring the membrane potential to around -40mV
trans-orbital lobotomy
pioneered by Freeman, procedure where he'd go in through the eye to remove part of the frontal cortex (done to 20,000 Americans)
leukotomy
pioneered by Moniz - severing white matter connections from the frontal cortex to the rest of the brain using ethanol to kill neurons
difference between place cells from dorsal to ventral MEC
place cells echoed what was found in grid cells, in that place cells in the dorsal MEC had smaller place fields that gradually became larger as one recorded more ventrally
topographic organization of place fields in the hippocampus
place fields are distributed all around the environment, regardless of the physical placement of the pyramidal cells in the hippocampus
place fields and isotropic scaling
place fields are largely insensitive to isotropic scaling of the environment
place fields and landmark shape
place fields are largely insensitive to landmark shape (with or without the animal's knowledge)
place field sensitivity to external cue placement vs. self-motion cues
place fields are sensitive to external cue placement when these don't contradict self-motion cues
otoacoustic emissions
play a sound into the ear and record the sound that comes out, which will be different if the era is functioning
limbic system
plays a central role in emotions, in relating visceral responses to emotional states, and in tagging emotional significance of memories
fixation plane
point at which both eyes have an image projected onto the fovea, no disparity here
melencephalon
pons and cerebellum
hyperpolarizing mechano-sensitive ion channels
potassium channels that allow potassium to flow out, hyperpolarizing the cell
ocular dominance columns in layer 4C of the visual cortex
preference for input from one eye that alternates from one clump of cells to the next
neurotransmitters in the parasympathetic nervous system
preganglionic cells release acetylcholine to ganglia, activating nicotinic (ionotropic) acetylcholine receptors and then the postganglionic fibre releases acetylcholine, activating muscarinic receptors on the target tissues
neurotransmitters in the sympathetic nervous system
preganglionic cells release acetylcholine to ganglia, activating nicotinic (ionotropic) acetylcholine receptors and then the postganglionic fibre releases norepinephrine, activating adrenergic receptors on the target tissues
unimodal areas
primarily process a given sense
important brain areas for voluntary motor control
primary motor cortex, thalamus, midbrain, red nucleus, pons, cerebellum
general sequence for cortical sensory processing
primary somatosensory unimodal cortex to unimodal association cortices to multimodal association cortices
long term implicit memory brain areas
priming uses the neocortex, procedural uses the striatum, associative learning emotion responses use the amygdala, while associative learning skeletal musculature uses the cerebellum, non associative learning uses reflex pathways
cerebellar-like anatomy of the electric fish
principle cells get info from sensory input layer and then granule cells provide corollary discharge signals, so the principle cells get an efference copy and sensory input which project to higher brain areas
What can be said of cortical areas adjacent to A1?
process multimodal info
population code
produced by overlapping receptive fields, so that you activate many afferents at once, allowing the brain to localize where the stimulus came from
reinforcer (operant conditioning)
produces an increase in the response that preceded it
lesion of the hippocampus or association temporal cortex
produces clear impairment of explicit memory
layers II, III, and IVB of the primary visual cortex
project to other layers of the visual cortex
Where do afferents from hair cells project?
project via the 8th nerve to the cochlear nucleus
layer VI of the neocortex
projections to the cortex and thalamus
layer VI of the primary visual cortex
projects back to the dLGN
layer V of the primary visual cortex
projects to the pons and the superior colliculus to control visually guided voluntary movements
mood
prolonged emotional state, may be dependent or independent of immediate circumstances (involves the amygdala and anterior cingulate gyrus)
What happens when RUNX3 is maintained around day 14 of embryogenesis?
proprioceptors develop
language development in vitro
prosodic patterns of speech (but not phonemes) can be transmitted to the fetus
medial septum
provides a major projection into the hippocampus and MEC, so lesions to the medial septum mimic the behavioural deficits of hippocampal lesions on spatial memory tasks and eliminate theta oscillations throughout the medial temporal lobe
0 visual signal
pure noise
overview of cells in CA3
pyramidal cells in layer 5 that send their apical dendrite to the middle of the hippocampus (hippocampal fissure) and their basal dendrite to oriens
overview of cells in CA1
pyramidal cells that send their apical dendrite to the hippocampal fissure and send basal dendrite out to stratum oriens
retrieval
recall and use of stored info (creative process)
characteristics of implicit memory
recalled unconsciously, usually involves training, reflexive perceptive motor skills, knowing how to do something, localized to basal ganglia and cerebellum
retinal ganglion cells
receive input from bipolar cells and send output to the brain through the firing of action potentials
inputs to CA1 in rats
receives 4,500 basilar and 6,500 apical synapses from CA3 Schaeffer collaterals and 2,500 synapses from EC layer III
layer 4C of the visual cortex
receives all direct output from the LGN responds to input only from one eye
superior colliculus
receives around 10% of visual output from the retina and is a primordial visual brain
lateral geniculate nucleus (LGN)
receives info from the retinal ganglion cells and outputs to the visual cortex
What is the wiring of layer 4B of V1?
receives input from layer 4Calpha and projects to V2 thick stripes and MT
medial vestibular nucleus
receives input from the vestibular system and sends info to the nucleus prepositus and the dorsal tegmental nucleus (codes for left or right movement)
layer IV of the primary visual cortex
receives inputs from the thalamus (dLGN), which are monocular projects to other layers of the visual cortex (layers III and IVB, which are binocular)
hypothalamic mechanisms
receives sensory info from the whole body and from brain regions involved in cognition, emotion, and memory and then contains internal sensory neurons that respond to changes in local temp, osmolality, glucose, etc.
What form of language development occurs around 7-8 months?
recognize words by learning the probability that one sound will follow another
Colour of the longest wavelength of visible light
red
two types of colour-opponent retinal ganglion cells
red / green and blue / yellow
connecting correlation to signal detection theory
reducing correlation increases d' by making the distributions skinnier (reducing variability due to noise), increasing the difference between the distributions, thereby making it easier to correctly perceive
anatomical connectivity
refers to the axonal projection from one area to another
functional connectivity
refers to the statistical dependence (correlation) between the time courses of activities in different areas
What do high spatial frequencies imply?
regions where pixel values change rapidly
body weight
regulated by a set point that can vary with stress, palatability of food, exercise, environmental, and genetic factors
brightness measurements in photoreceptors
relative to what's around
peptidergic nociceptors
release glutamate and neuropeptides and sense temperature-related pain
What is the cause of vagal stimulation in the heart?
release of Ash onto muscarinic receptors, leading to the slowing of cardiac AP
removal of external cues and place fields
removal of external cues leads to random remapping of place fields
habituation to repeated stimulation in aplysia
repeated stimulation leads to weaker postsynaptic responses in motor neurons see depression at motor neuron correlated with behavioural dishabituation
decibels
represent sound intensity in a way that corresponds to perceived loudness
extrapersonal space
represented in the posterior parietal cortex - an understanding of where something is in relation to oneself
slope of a psychometric function
represents sensitivity - at its max at 50% perception
job of central sensory neurons
respond more selectively
job of peripheral sensory neurons
respond to most stimuli
processing of angles in V1
respond to one orientation
area V4
responds to complex shapes
law of effect
responses that produce a satisfying effect in a particular situation become more likely to occur again in that situation and responses that produce a discomforting effect become less likely to occur again in that situation
storage
retention of memory over time
bilateral memory specialization in the hippocampus
right hippocampus affects spatial memory left hippocampus affects words, objects, or people
tinnitus
ringing, buzzing sounds in the ear or head caused by changes in blood flow or muscle activation, noise-induced hearing loss or as a side effect of some medications
organization of the developed mesencephalon
roof = tectum floor = tegmentum CFS filled core = cerebral aqueduct
coronal brain slices
rostral - caudal
contour integration in V1
same structure as endstopping, but you find excitatory connectivity with neighbours instead of inhibitory, so that lines of similar orientation stand out against a background of random orientations
What happens when an animal is put in a hairpin maze and one records from MEC grid cells?
see that there's fragmentation of the grid in grid cells
hyperactivity of the hypothalamic pituitary axis
seen in severely depressed patients
LTP and place fields
selective knockout of LTP doesn't prevent the formation of place fields, but LTP mechanisms are necessary for the retention (stability) of place fields
osmoreceptors
sense osmolarity (can be in the hypothalamus)
supraoptic nucleus
senses the osmolarity of fluid
copy element
sent to sensory neurons, which will then do a comparison between actual sensory input and efference copy, allowing the sensory system to filter out reafferent input, enabling perception
Why are the tight junctions between hair cells important?
separate the endolymph and perilymph such that the endolymph is just bathing the tops of the hair cells and the bottoms are bathed in perilymph
antipyretic area
septal nuclei near the anterior commissure that give us our response to fever
low temporal frequencies in images
sequences of images is dominated by low temporal frequencies
transient stress response
sharpens cognition, increases energy, gives a feeling of confidence
What is thought to be associated with Broca's area?
short term memory for language
neurometric curve
sigmoidal function - stimulus intensity on x-axis and % neural unit response on the y-axis
psychometric function
sigmoidal function and on the y-axis is perception of a sensory stimulus (sensory detection %) vs. its intensity on the x-axis
What is the relationship between hair bundle displacement and receptor potential?
sigmoidal, demonstrating saturation (point at which all channels are closed and point at which all channels are open)
LGN receptive fields
similar to those of retinal ganglion cells, with magnocellular and parvocellular and on centre / off surround or off centre / on surround
virtual reality experiments to study human hippocampus
single neuron recordings from patients suffering from epilepsy intracranial electrodes used to locate the seizure focus patients played a "taxi driver" computer game
What counts as microscopic scale in the nervous system?
single neurons and their synaptic connections
simplified neural circuit of aplysia
siphon stimulation to LE sensory neuron to L7 motor neuron to gill
What happens in the inner ear?
site of auditory mechanoelectrical transduction
organ of Corti
site of sensory transduction, where hair cells sit on the basilar membrane, with stereocillia on top of them that extend into the tectorial membrane
requirements of normal birdsong
social interaction and auditory feedback
Which brain area is particularly good at integrating form and motion?
some cells in the anterior superior temporal polysensory area (STPa)
How can V1 cells select for time?
some cells respond more sluggishly than others, so LGN inputs feeding into V1 are all working on different time scales
double rotation rodent place field experiment
some cells' place fields primarily influenced by positions of distal cues, some influenced by proximal cues, and some show random mapping, but when we return to standard, place fields always go back to where they used to be
adrenal medulla's role in the stress response
some of the sympathetic response goes to the kidney, where chromatin cells act as postsynaptic neurons, releasing hormones like adrenaline
thalamus motor pathways
some subnuclei involved in motor control
isolated songbird song
song develops spontaneously, but looks very different from that of a tutored bird (missing phrases, syllables, etc.)
signalling molecules for brain regional specializations
sonic hedgehog (shh) bone morphogenic proteins (bmp) wnt family proteins
phonemes
sounds
For which sounds are the tensor tympani and stapedius activated?
sounds >80dB
language perception in songbirds
species predisposition, will listen and memorize, critical period closes
base of the basilar membrane
stiff and narrow, responds to high frequencies (20,000 Hz), closest to the oval window
complex cells in the visual cortex
still orientation tuned, but have no detectable receptive structure (no on or off centre receptive field) orientation of tuning a complex cell can't be predicted from its response to small spots of light (doesn't care if it's a dark or light spot)
pitch invariance
still understand what's being heard, even if the words are at different pitches
concentration invariance
still understand what's being smelled, regardless of odourant concentration
reafference
stimulus input that derives from an observer's own movements (self generated)
visual impairments that can be caused by stroke
stoke can take out the optic radiation or part of the occipital love leading to the loss of one part of the visual field that's the same in both eyes
vocal emotion cues
stress, timing, and intonation in language
What do low spatial frequencies imply?
strong local correlation
submodalities
subclasses of receptors that each respond to a limited range of stimulus energies
layer V of the neocortex
subcortical
mechanical tickling experiment setup
subject moves a machine that connects to a computer and a second machine has a feather that will touch the subject
posterior parietal cortex lesion leading to visual neglect for objects
subjects cannot compute spatial relationships to plan movements (can't draw objects, for example)
What is the region where efferents come from that relate to the auditory system?
superior olivary complex in the brainstem
What is the first site of binaural interactions?
superior olivary nucleus
LTP in songbirds
synapse-specific and activity dependent requires both pre and postsynaptic activity NMDA receptors and calcium dependent
experience dependent changes in place fields
synaptic connections can be potentiated to be strong enough to cause an AP, leading to changes in place fields based on experience (rat running laps in one direction leads to place field extended to the left)
what mediates dishabituation and sensitization at the behavioural level?
synaptic facilitation mediated by neuromodulators (including serotonin in aplysia)
What governs how we use words to make an infinite number of sentences?
syntax
mechanism of short-term facilitation by serotonin
tail shock causes AP from sensory neurons, facilitating the interneuron to spring to action causing serotonin-containing vesicles to exocytose and release serotonin, which bind bind metabotropic GPCRs on presynaptic terminal, which can either activate PKA, allowing potassium to flow out, hyper polarizing the presynaptic membrane, decreasing the probability of vesicle exocytosis or render potassium channels less conductive, meaning the membrane becomes more depolarized, allowing calcium to enter, causing more vesicle exocytosis (sensitization vs. dishabituation depends on how much serotonin is released)
optimal redundancy reduction
take lots of images of natural scenes and find the minimum set of filters that can represent them and these optimal filters look like simple cell receptive fields
how to make a tuning curve
take the number of action potentials fired in response to a stimulus and plot it on the y-axis with stimulus value (for example, orientation) on the x-axis to make a tuning curve
What does the centre of the expansion stimulus tell MST neurons?
tells you in which direction you're going
velocity of a sinewave grating
temporal frequency / spatial frequency can be measured with a drifting sinewave grating
working memory
temporary storage of info that is responsible for the transient holding and processing of new and already-stored info
Muscles that limit motion of the ossicular chain to protect the ear against loud noises
tensor tympani (attached to malleus) and stapedius (attached to stapes)
auditory brainstem response
test in which sounds are played and the waveform of neurons in the auditory brainstem is measured through electrodes
synaptic ribbon
tethers a large number of synaptic vesicles to the hair cell's presynaptic active zone so that there can be a rapid release of glutamate
contrast sensitivity
the ability to detect differences in light and dark areas in a visual pattern
acuity
the ability to differentiate one stimulus from another
thinking
the ability to have ideas and to infer new ideas from old ones, which occurs in the absence of language
scotopic vision
the ability to perceive visual stimuli in near darkness due to the activity of rods
photopic vision
the ability to perceive visual stimuli under bright light conditions due to the activity of cones
cortical magnification factor
the amount of space in the cortex occupied by an object of a given size (bigger E -> smaller Mc)
HPA and the amygdala and hippocampus
the amygdala upregulates the HPA, while the hippocampus dampens the HPA response
receptive field of senses
the area with the receptive surface where stimulation excites the cell
Nativism
the belief, defined by Chomsky, that there is innate neural circuitry dedicated to language
labeled-line code
the brain knows the modality and location of every sensory afferent
light adaptation
the change in operating range of the visual system based on the light intensity
how do we get a perceived stimulus?
the combination of an efference copy and the reafferent stimulus
feelings
the conscious perception of emotional responses mediated by the cerebral cortex, cingulate cortex, and frontal lobe
light refraction in the eye
the cornea and the lens refract light to focus it on the retina (cornea does most of the refraction)
light refraction accommodation for near vision
the cornea is only successful over certain depths, so now the lens, controlled by ciliary muscles, plays a significant role
main brain structural difference between primates and other vertebrates
the cortex
adaptation of sensory receptors
the decrease in a sensory neuron frequency of firing due to constant stimulation (rapidly and slowly adapting)
What happens to place fields with expansion of the environment?
the firing field expands
Where on the body do we have highest acuity for somatosensation?
the hands and face
Alzheimer's typically affects which part of the brain?
the hippocampus, particularly the entorhinal cortex
How do LGN inputs feed into V1 in cases of motion in the preferred direction?
the inputs from LGN arrive synchronously, leading to a large output from the simple cell
presbyopia
the lens gets stiff and is unable to accommodate for near vision
astigmatism
the lens or cornea are not spherical
temporal correlation in natural images
the luminance values of individual pixels usually remain constant over short time intervals
short term vs. long term sensitization
the more consecutive tail shocks and the more days, the more potentiation of behavioural response (few tail shocks lead to short-term sensitization, whereas many tail shocks lead to long-term sensitization)
To what does the malleus connect?
the oval window
central executive
the part of working memory that derives from the frontal lobe and directs attention to relevant info and coordinates cognitive processes, especially when we need to do more than one task at a time
phonological loop
the part of working memory that holds and processes verbal and auditory information
How can we use anxiety to understand the difference between emotion and feelings?
the physical state leads to conscious perception cause you're not consciously scared, but your body is reacting like it's scared, making you feel scared
What parts make up the external ear?
the pinna, the external auditory meatus (canal), and the tympanic membrane
threshold of a psychometric function
the point at which the stimulus intensity is perceived half (50%) of the time
so, what's happening in the mechanical tickling experiment?
the predicted sensory stimulus (efference copy) is compared to the actual stimulus (reafferent stimulus) and if there is a discrepancy, then the subject perceives the stimulus as causing a tickling sensation
memory
the process by which knowledge we've learned about the world is encoded, stored, and retrieved
tolerance
the progressive adaptation to the dosage that produces euphoria due to homeostatic responses
dynamic range of light
the range of light intensity that can be distinguished by photoreceptors, but that changes as a function of light intensity
endstopping in the visual cortex
the reduced response to long edges, showing size selectivity
signal detection theory
the response to a stimulus depends both on a person's sensitivity to the stimulus in the presence of noise and on a person's response criterion
dishabituation
the restoration to full strength of a response to a stimulus that had previously become weakened through habituation
attention
the selective filtering and modulation of behaviourally relevant info
morphemes
the smallest meaningful units of language (like a suffix)
auditory threshold
the smallest sound intensity required to produce action potentials
tonotopy
the systematic organization within an auditory structure (like the basilar membrane) on the basis of characteristic frequency
common theme across sensory systems for sensory processing
the thalamus projects to the primary sensory cortical areas
What happens when the psychometric curve shifts left?
the threshold went down, meaning that you were able to detect a weaker stimulus half the time
cerebellum and the timing of movements
the timing of movements requires the cerebellum - with lesions, an animal can't learn to anticipate a puff of air in its eye, for example
To what does the stapes connect?
the tympanic membrane
continual neurogenesis in the hippocampus of adults, as shown by the London taxi driver experiment
there is a positive correlation between time as a taxi driver and posterior hippocampus size, as well as a negative correlation between time as a taxi driver and anterior hippocampus size
What happens when an animal is put in a hairpin maze and one records from hippocampal place cells?
there's fragmentation of place field, just like there was for grid cells
Cortical area V2 organization
thin, pale, thick stripes
What did Bruce McNaughton find?
thought that EC must be the source of place codes that go to place cells in the hippocampus, but found that this wasn't true when he looked in the EC
ADHD and memory
thought to involve deficits in working memory
How do the neurometric and psychometric curves compare when perception is greater than neural output?
threshold of the psychometric curve < threshold of the neurometric curve sensitivity of the psychometric curve > sensitivity of the neurometric curve
How do the neurometric and psychometric curves compare when neural output is greater than perception?
threshold of the psychometric curve > threshold of the neurometric curve sensitivity of the psychometric curve < sensitivity of the neurometric curve
What happens when the psychometric curve shifts right?
threshold went up, meaning that it takes a stronger stimulus to be able to be perceived half the time
After the photoreceptors, where does light go?
through the horizontal and amacrine cells, where more adaptation occurs
How is the magnitude of the stimulus conveyed?
through the magnitude of receptor potential, which affects the frequency of action potentials, which is then converted to the magnitude of neurotransmitter release
How is anatomical connectivity measured?
through tracer injection
What determines specification of sensory neuron subtype, besides transcription factors?
timing of the migration start
What controls drinking behaviour?
tissue osmolarity and vascular volume
What is the purpose of brain experiments?
to tell us what is happening in the brain
What is the purpose of computational models of the brain?
to tell us why or how something happens
Where does layer 4C of V1 project?
to upper layers, which project themselves to extrastriate cortex
caudal
towards the back
ventral
towards the belly
medial
towards the midline
rostral
towards the nose
lateral
towards the outside
dorsal
towards the top
vision restoration therapy
training people to use the superior colliculus to regain the ability to detect motion
RUNX1
transcription factor that drives trkA activation
RUNX3
transcription factor that drives trkC activation
What determines the differentiation of sensory neurons?
transcription factors
What happens in the middle ear?
transmission of mechanical energy
What causes neuron subtype diversification?
trk receptors, which are controlled by transcription factors
What is the purpose of cells in layer 4B of V1?
tuned for motion direction and
scala vestiboli
upper compartment of the cochlea that contains perilymph
evidence for grid cells in humans
used fMRI and found that lots of head direction cells in MEC are also aligned to these axes
pleural ganglion and pedal ganglion in aplysia
used for locomotion
Why would it be a good thing for the afferent response to change as a result of efferent input in the auditory system?
useful to increase the dynamic range in situations of noise, quieting the system, and allowing for the comprehension of speech in a noisy environment
How was the functionality of of OA discovered for sure?
using fluorescent markers - red shows that those neurons are innervated at the knee joint, but are not nociceptors, while green shows that they're nociceptors, so green and red are nociceptors that innervate the knee joint
How is functional connectivity measured?
using the Pearson's correlation coefficient to look at the similarity of time courses
How can data from many subjects' brains be aligned?
using the Talairach system (stereotactic coordinates)
brain areas that are important in classical conditioning
vermis and nucleus interpositus of the cerebellum, as well as the amygdala
ocular dominance columns
vertical columns consisting of neurons in V1 that receive signals from the left eye only or the right eye only and is still present in people who lose one eye in adulthood cause the organization of the visual cortex is determined at this point
mechanism of long-term facilitation by serotonin
via signalling pathways, hydrolases cause more glutamate vesicle production and also cause the growth of new synaptic connections
What provides the subjective sensation of sound?
vibration of air molecules (pressure waves)
colour of the highest frequency of visible light
violet
referred pain
visceral and somatic pain afferents commonly synapse on the same neurons in the spinal cord, leading to the perception of pain in a location that is not being stimulated (i.e. people feel pain in the left arm during a heart attack)
somatic nervous system
voluntary responses, targets skeletal muscle
redundancy reduction
wanna block out low spatial frequency image sections (cause very redundant), but don't wanna block out high spatial frequencies
treponema pallidum
was a bacterium that is the cause of syphillis, which is a progressive disease that causes mania, followed by cognitive deterioration and eventual paralysis and death
spectrograph
way in which human speech can be represented by frequency
pain signal to the medial prefrontal cortex
what tells you that pain is uncomfortable
EOD command experiment with electric fish
when EOD command was paired with an excitatory or inhibitory stimulus, the response was potentiated and depressed respectively, but after, if the EOD command is presented alone, the response is opposite (depressed for the cell that previously had an excitatory stimulus and potentiated for the cell that previously had an inhibitory stimulus)
rodent hippocampus lesion platform experiment
when SHAM lesioned, animal has memory of where the platform used to be located when CA3 lesioned, exact spatial location of the platform is fuzzy when complete hippocampal lesion, rat can't remember platform location at all
songbird song "syntax"
when a bird is exposed to overlapping snippets of the song in a backwards order, it was able to order the sequence correctly
afferent synchrony
when action potentials occur together, which the brain could use to tell it that something is happening, even if the firing rate hasn't changed
temporal responses in LGN
when an image is flashed, there is an excitatory response that is almost immediately followed by an inhibitory response (like centre / surround organization in the spatial domain)
colour adaptation
when cones of one type tire, we adapt, leading to the illusory perception of the opponent colour
binocular disparity
when looking at an object, each individual eye has its own input of where the image is relative to the fixation point (where the image is projected onto both foveas) and these inputs can be compared to relay depth
NMDA receptors and memory
when mice were given APV, blocking NMDA receptors, they were unable to remember which area they had been trained to go to
amblyopia
when one eye tends to be dominant due to the incorrect development of the cortex, but you can make kids wear an eye patch, so that the cortex develops properly into ocular dominance columns
motherese
when people speak to infants using a higher pitch and slower tempo speech with exaggerated intonation, helping infants recognize sounds
hyperalgesia
when something already painful produces a much greater painful sensation
allodynia
when something innocuous now produces pain
In what case would neural output be greater than perception?
when the brain doesn't have access to all the info in the afferent's activity or the brain is adding noise to the afferent's activity
In what case would perception be greater than neural output?
when the brain is combining the activity of many afferents to average out the noise
rate remapping
when the same place cells are active, but there's a firing rate change due to sensory changes in the environment
defensive conditioning
when the unconditioned stimulus is noxious
appetitive conditioning
when the unconditioned stimulus is rewarding
global remapping
when you turn off or completely change the location of firing of place cells due to being in a totally new environment
lateral mammillary nucleus
where head direction cells first appear
anterodorsal thalamic nucleus
where most head direction cells are
cerebellar layers
white matter, granule cell layer, purkinje cell layer, molecular layer
achromatic off centre / on surround retinal ganglion cell
will fire action potentials when darkness hits the centre of the receptive field and will fire action potentials when light hits the surround
achromatic on centre / off surround retinal ganglion cell
will fire action potentials when light is in the centre of the receptive field (compared to the background) and will fire action potentials when darkness (compared to the background) hits the surround
What will happen if you lesion A1 unilaterally?
will not affect perception of sound frequency, but will affect sound localization of the contralateral side
posterior parietal cortex lesion leading to representational neglect
with damage to one side of the posterior parietal cortex, subjects can only recall landmarks to their right when asked to image their location
motor learning and cerebellar lesions
with lesions to the cerebellum, subjects cannot adapt when they wear prison lenses and will continually throw putty off-target, but their motor skills themselves are not impaired, just learning
What is the significance of changes in blood flow, blood volume, or oxygen consumption in terms of fMRI signalling?
with these changes come different deoxy-HB concentrations
drugs that block mechano-sensitive channels
work very well in blocking allodynia, but are not a viable solution for therapy cause they're way too expensive since they must be extracted from a Chilean tarantula
What would happen if you severed the 8th nerve?
would lose hearing only in that one ear
Are head direction cells impaired in ADN after lesions of the dorsal tegmental nucleus?
yes
Are head direction cells impaired in ADN after lesions of the lateral mammillary nucleus?
yes
Are head direction cells reactive during sleep?
yes
Are theta oscillations present in REM?
yes
Do head direction cells in the presubiculum require input from ADN?
yes
Is tonotopy preserved in the cortex?
yes
Do grid cells persist in complete darkness?
yes, something is internally generated by the system
language production in songbirds
young bird will have a plastic song, will receive feedback, will obtain song crystallization
