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PSYC 370 > MT 2 > Flashcards

MT 2 Flashcards

1
Q

stretch reflex inhibition

  • inhibition at circuit level –> importance
  • feedforward –> signal movement
  • feedback –> signal movement
A

inhibition at circuit level: important for creating signals that arent constant and loud –> change firing code
- if all axons traveling to brain were constantly activated it would be chaos

feedforward: regulates which neurons will fire APs –> signal goes forward to inhibitory neuron to stop movement (blocks)
- signal excites extensor muscle and inhibits flexor muscle (splitting signal)

feedback: constrains activity –> provides signal once it is flexing so you can stop (eg. so you don’t hit yourself in the face when you pull back)
- extensory feeds back to itself and inhibits itself to stop extensor (converging signal)

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2
Q

divergence vs convergence

A

divergence: one neuron synapses onto multiple neurons –> information spreads, signal can serve different purposes (synchronization, one signal can have many actions) –> sensory
convergence: many neurons synapse onto a single neuron –> integration of diff types of info, way to control signal (don’t want reflex every time you touch something, want appropriate response), leads to multiple neurons having one action –> motor

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3
Q

information encoding

  1. amplitude
    - more stretch?
    - AP evoked?
  2. duration
    - longer duration?
    - over time what happens to signal?
  • trigger zone
A

muscle spindle senses physical changes –> 2 signals control number of APs (code intensity and duration) –> changing the amount of ions flowing

  1. greater amplitude of stretch = higher freq of APs
    - how much current is coming into the muscle spindle –> let ions flow
    - more stretch = bigger amplitude = more current = more APs (freq) = more NTs released (due to depol of VG ca++ channels)
    - stretch may not evoke AP at all (depends on amt of NTs released)
  2. longer duration of stretch = more APs over time
    - longer duration = more current = more AP = more NTs
    - over time, signal gets weaker even tho stretch amplitude stays the same (lower EPSP strength over time)
  • there’s no VG channel directly in place, so AP happens a bit later on dendrite (trigger zone)
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4
Q

summation of synaptic potentials

  • temporal summation
  • spatial summation
A

temporal summation: consecutive EPSPs from the same axon can summate to produce AP –> reach presynaptic bouton, more EPSPs = more likely to cause AP –> if signals are close enough together EPSPs can add up to produce AP

spatial summation: concurrent/consecutive EPSPs from separate cells can also summate to produce an AP
- 2 axons on one dendrite = more current = more depol = more likely AP

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5
Q

sensory perception

  • receptors
  • perception
  • sensation vs reality
  • proprioception
A

sensory modalities have specially designed receptors that convert particular stimuli from the world into APs –> relative activity of populations of neurons forms a representation (percept) for that sensory stimulus

  • not everyone perceives world same way even with same stimulation
  • what we sense is not actually what is in the world, it is just what exists in our brain

eg. proprioception: balance from inner ear + feedback from muscles

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6
Q

psychophysics

  • definition
  • simple relationship
  • example
A

psychophysics = investigation of relationship btwn physical stimuli, sensation and perception

simple relationship: linear (not always, could be logarithmic)

eg. can measure neuron responses with electrophysiology
- stronger skin indentation = stronger neuron responses

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7
Q

visual performance

- 4 ways to test

A

Snellen chart: try to read letters –> visual acuity (how well we can see things from far away)

absolute threshold: minimal amt of light needed to detect light –> control amt of photons coming out (humans = 6-12 photons)

spatial resolution: test w vertical bars –> spatial freq of grading
- cycles/degree (cpd) of visual angle –> how space is organized to visual scientists (in degrees)

facial recognition

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8
Q

visual disorders

  • focus
  • autism
  • high spatial frequency
A

diff aspects of sensitivity are diff for diff visual disorders

  • some ppl focus on details instead of whole picture
  • ppl with autism might be overperforming (too detail oriented –> more sensitive to higher spatial freq)
  • higher spatial freq = more detailed aspects; lower = more coarse image
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9
Q

levels of visual processing

  • low
  • intermediate
  • high
A

low level: combines simple features –> parallel processing, colour (detected by cones), orientation, contrast/brightness, distance/disparity (2D vs 3D), movement, texture

intermediate level: take local cues

  • orientation = diff surface properties (which lines are together)
  • colour contrast + orientation = shapes
  • binocular vision (something in front/behind –> depth)
  • moving = kinematic info –> what parts are moving at the same time

high level: object identification –> putting everything together

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10
Q

types of processing

  1. bottom-up processing
    - associated with?
    - perception differences
  2. top-down processing
A
  1. bottom-up processing: taking small things and building them up into a higher level processing
    - associated with convergence –> each level of processing is converging into a smaller number of neurons which have receptive fields with more advanced processing skills
    - perception is different, depending on experience –> expectations, priming, env, learning, etc all matter
  2. top-down processing:
    expectations/priming: can influence what you see
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11
Q

retina & sensory transduction

  • rods and cones connecting to?
  • J cells
A

rods and cones connecting to bipolar cells
J cells: type of retinal ganglion cells for motion –> responsible for detecting motion in one direction –> all point in same direction

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12
Q

electromagnetic spectrum

  • visible light
  • bees
  • snakes
  • evolution
A

visible light: only a fraction of full EMS –> 400-790nm
- colours of the rainbow
- bee vision is very different (see UV rays –> target flowers)
snake vision see infrared (body temp) –> able to see hiding prey

  • products of evolution to make species more successful in env
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13
Q

eye diagram

  • retina
  • lens
  • pigment epithelium
  • fovea
  • signal transmission path
A

retina: inner back layer
lens: focuses light; can stretch or contract
pigment epithelium: back layer (dark colour) –> helps recycle photoreceptor pigments
fovea: centered dent –> where lens focuses light; bipolar and retinal ganglion cells are pushed to the side so light can reach photoreceptors better (get a better image); allows for less light dispersion
- signal transmission starts in the back –> light has to pass through cells to activated photoreceptors, then propagates forwards to bipolar/retinal ganglion cells and goes to optic disk (blind spot) –> exits eye through optic nerve

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14
Q

lateral connections

  • horizontal cells
  • amacrine cells
A

horizontal cells laterally connect rods and cones (cones are much smaller and weirder shaped than rods)
amacrine cells laterally interconnect bipolar and rgcs

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15
Q

rods and cones

  • morphology (5 parts)
  • opsin
  • light stimulus
  • rods (2)
  • cones (2)
A

morphology: rods and cones have similar basic structures
- outer segment = stacks of membranous disks that contain light-absorbing photopigments –> can fit more in when there is overlap/diff shapes
- inner segment contains cell machinery
- cell body + synaptic terminal
- both release glu from axon

opsin: a light-sensitive protein associated with membrane channels –> light stimuli cause conformation change in response to absorbing photon = change in conductance of the membrane
- light hitting hyperpolarizes cell (normally at -40 and always releasing some glu = dark current; but when light hits it goes to -70mV, causing much less glu to be released = change in firing)

rods:
- have rhodopsin
- look like little pancakes separate from outer membrane (free floating discs)
cones:
- have cone opsin
- all folded and connected to outer memb (continuous)

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16
Q

photosensitivity

  • diff opsins
  • what are rods for
  • rods (what do their opsins do?)
  • cones
A

different opsins have diff sensitivity to waves of light

rods: stimulation of rods seen as grey, highly sensitive, low-light vision
- if rod is activated rhodopsin codes it as black and white; no colour vision for rods, but they’re much more sensitive to light than cones –> more stacked disks = more photopigment

cones: simultaneous activity of diff cones = basis of colour vision (population coding)
- less sensitive because it is used in the daylight

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17
Q

colour vision

  • cones compared to rods
  • spectrum
  • visible light range
  • 3 diff types of cone opsins
  • shining light at 520 vs 600 (how do cones react)
  • population coding
A

much less sensitive than rods; need more light to hyperpol
- each one comes with its own absorbable spectrum (range of light that activates it)

visible light = 400 - 790nm

cones have 3 opsin types:

  1. S cones (blue): short wavelengths
  2. M cones (green): medium wavelengths
  3. L cones (red): long wavelengths (but peak is more yellow… )

if you shine light at 520nm and 600nm

  • green cone would have high activity at 520, but low activity at 600nm
  • red cone has medium activity for both
  • must look at a combination of activity (population coding) –> at 520 you see green, but at 600 you would see something like orange
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18
Q

rod-cone distribution

  • rods
  • cones
  • degrees of eccentricity
A

rods: ~100mil, predominantly periphery (night vision)
cones: ~6mil, predominantly fovea (day vision; high acuity –> eg. reading)

degrees of eccentricity: higher degree = further from fovea
- rods highest around 20 degrees

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19
Q

cone/rod circuitry (connections)

- convergence and sensitivity

A

cones: low convergence, high sensitivity (1 cone - 1 bipolar cell - 1 retinal ganglion cell –> have to focus on smaller details while in the light, so you want lower convergence rates)
rods: high convergence –> many rods converge on some bp cells which converge on 1 rgc –> receptive field much bigger, but less clear vision (less acuity)

20
Q

receptive fields

  • definition
  • periphery vs fovea
  • retinotopic map (rgc to where?)
    1. on-center
    2. off-center
  • small middle vs big middle
  • small outer vs big outer
  • complete overlap
    (exercise: also think about what happens for on center!)
A

receptive field = circular region on retina that elicits changes in firing in a given sensory neuron; often have both excitatory and inhibitory regions
- bigger in periphery because there are more receptors contributing to the firing of rgcs (much smaller in fovea because of low convergence rates)

retinotopic map: rgcs send to lgn in thalamus (sensory relay station)

  1. on-center receptive field: inhibitory surrounding, excitatory in the middle –> inc in firing rate when light hits the center
  2. off center: dec in firing rate when light hits center (bc inhib is in the center) –> adding darkness (taking away light) also increases firing rate
    - small middle = slight dec in firing when light turns on, inc in firing when light turns off (adding darkness)
    - big middle = more pronounced effects
    - small outer = slight inc in firing when light on, slight dec when light turned off
    - big outer = more pronounced effects
    - complete overlap = no change in response
21
Q

why do we have both on and off center?

A

timing: for on-center, spikes per second increases when light goes on and then returns to normal once off, but you need to wait a certain amt of time before the next spike happens to know that its back to normal
- off-center is complimentary –> shows you when light turns off (on-center and off-center in one receptive field have complimentary signals)

22
Q

bipolar cells

  1. “on”
    - in the dark
    - add light
  2. “off”
    - in the dark
    - add light
A
  1. “on”: metabotropic glu receptors (mGluR)
    - in the dark: continuous glu release from photoreceptor hyperpolarizes bipolar cell
    - add light: less glu release from photoreceptors (photoreceptors now hyperpolarized) = less glu binds to mGluR –> depolarization effect in bipolar cell (sign flipping –> hyperpol in photoreceptor causes depol in bipolar cell in response to light)
  2. “off”: ionotropic glu receptors
    - in the dark: glu binds –> ca++ channel opens –> depol cell
    - add light: less glu released from photoreceptors (hyperpol) –> less bound to ionotropic receptors = cell becomes more hyperpolarized (sign conserving –> hyperpol in photoreceptor causes hyperpol in bipolar cell in response to light)
23
Q

lateral inhibition

  • stimulus
  • lateral connections
  • intensity differences –> effect
  • result
  • priors
A
  • intense light bordered by dim light onto retina
  • receptors have lateral connections = activity in one receptor affects (inhibitory) other receptors nearby
  • receptors bordering stimuli of different intensity will receive different levels of inhibition = those receptors will have a diff firing rate than other receptors nearby
    Result: enhancement of contrast when there are diff intensity levels

*note: prior knowledge/predictions can affect perception of contrast

24
Q

retinal ganglion cells

  • number of types
  • mesh (on/off)
A
  • 20 types (polarity - on vs off; spatial resolution; temporal responsiveness; spectral filtering; motion)
  • unique representation of certain area
  • on and off rgcs interact and mesh together –> overlapping receptive fields
25
Q

cortical pathway

  • pathway (3)
  • contralateral
  • nasal retina
  • retinotopic map + visual space
A

retina > thalamus > visual cortex pathway

  • left visual field projected to right half of each retina then processed by right thalamus and right V1 (contralateral) and vice versa
  • nasal retina = half of retina closer to nose

retinotopic map: things beside each other stay beside each other in visual space all the way to the back of the brain (adjacent things stay adjacent from VF to retina to thalamus to V1 –> adjacent neurons represent adjacent areas in VF)
- more cortical real estate given to fovea (more cones in fovea) –> more processing power

26
Q 
cortical lesions
A: can only see left visual field
B: can only see right visual field
C: can only see nasal visual field
D: can see everything but outer right field
A

A: right optic tract or path to V1 - not reaching V1 but able to cross optic chiasm
B: left optic tract or path to V1
C: optic chiasm - peripheral visual field info (goes to nasal retina) not able to cross optic chiasm
D: right optic nerve –> left eye can still pick up light from middle left field, but right eye is not picking up anything = only right periphery not accounted for

27
Q

Neocortex

  • organization
  • mammals
  • layer 1
  • layer 2
  • layer 3
  • layer 4
  • layer 5
  • golgi, nissl and weigert stains
A
  • columnar organization –> 6 layers (some layers may be thicker in some parts of the brain)
  • neocortex part of mammalian brain –> foldy sheet covering entire brain (more real estate)

layer 1: small granule cells
layer 2: pyramidal cells
layer 3: (and 2) inputs from layer 4, has cortico-cortical output signals –> to cortical areas of brain (communicating with other parts)
layer 4: receives input from thalamus –> thalamus receives all info from LGN –> thicker in V1 than in motor cortex
layer 5: sub-cortical outputs to basal ganglia, limbic system

golgi stains selectively (random)
nissl stains cell bodies
weigert stains axons –> can see axons travel laterally and vertically

28
Q

orientation in V1

  • simple cells
  • cortical damage
  • circular vs bar of light (which layers?)
  • convergence
  • arrangement
  • blobs
A

simple cells: can be on- or off-center –> respond to bars/movement of light
- damage to certain areas in the back of the brain (eg. stroke) could affect certain areas of visual space = idea that there were receptive fields in the striate cortex just like in rgcs

  • rgcs, LGN, and layer 4 neurons have circular receptive fields
  • layer 3 neurons have bar of light receptive fields –> receptive fields line up = bar of light hits more middle than outer = net excitatory
  • convergence of on-center cells from layer 4 in a neocortical column
  • similar orientation columns are arranged closer together
  • blobs: neurons that are sensitive to colour in V1 (but they are not in every single column)
29
Q

cortical hypercolumns

  • definition, size, representation
  • clusters
  • isolate –> shows what?
  • same signal
A
  • when you put all properties together you get a cortical hypercolumn –> 1 mm diameter, represents a spot in space and shows all the info for that one spot (makes an image)
  • there are clusters of axonal branches in nearby periphery (axons go out, then go up at specific points)
  • if you isolate 1 hypercolumn (eg. horizontal line sensitive) and inject an adenovirus with GPF you can visualize where its going in V1 (where axons are going)
  • can see that axons are going to other horizontal sensitive cells (to check if they’re both active at the same time/getting the same signal = population coding)
  • same signal = makes pattern = put together an image (by combining all info from other axons too –> contours and outlines)
30
Q

sound

  • definition
  • amplitude
  • frequency
  • complexity
  • components
  • human range (real vs everyday)
A

sound: pressure wave traveling through the air –> differs in amplitude, frequency and complexity
Amp: bigger wave = louder
freq: longer wave = lower pitch
complexity: pure tones vs rich tones –> measured with timbre (why guitar G chord sounds diff from piano G chord)

  • when you put all the waves that make up a sound together there are additive and subtractive components
  • human range is 20Hz to 20,000Hz but everyday sounds are usually 250-6,000Hz
31
Q

ear anatomy

  • external ear (2)
  • middle ear (2)
  • inner ear (4)
A

external ear
pinna: outer funnel
auditory canal: focuses sound onto tympanum –> sound gets turned into physical vibrations

middle ear

ossicles: amplify vibrations –> signal better heard
- stapes looks like a stirrup (hits oval window) –> directs pressure waves into cochlea

inner ear
oval window: converts vibrations into pressure waves in cochlea –> cochlea filled with incompressible fluid –> if you put pressure on one side it has to go somewhere
round window: below oval window; allows movement of fluid (releases pressure)
cochlea: incompressible fluid inside scala vestibule and scala tympani (perilymph) –> scala media is filled with endolymph
organ of corti: basilar membrane, hair cells, tectorial membrane

32
Q

basilar membrane

  • what does it do
  • rows
  • stereocilia embedding
  • how do hair cell channels open?
  • tonotopic map (basilar membrane base vs apex)
A
  • vibrates in response to movement of cochlear fluid ​(bends in response to sound –> compression (at oval window) and rarefaction)
  • 1 row for inner, 3 rows for outer
  • stereocilia base embedded in basilar membrane, tips embedded in tectorial membrane
  • when you move basilar membrane up and down it moves hair cells back and forth because they’re pressed against the tectorial membrane –> causes them to bend, which opens mechanoelectrical channels near the tips

tonotopic map: sensitive to diff freq of sound

  • base: thick and rigid - peak sensitivity to high freq sounds - quick vibrations hit the thick part and run out of energy before it reaches apex
  • apex: thin and floppy - peak sensitivity to low freq vibrations - long wave can reach apex
33
Q

hair cells

  • axons?
  • glu
  • graded?
  • thickest stereocilia
  • tip links
  • hyperpol
  • adaptation
A
  • no axons, just a sensor –> afferent and efferent signals (sends signals out but also receives signals from brain)
  • release glu continuously (10% channels involved with stimulus transduction open at rest)
  • graded responses (depolarization or hyperpol) modulate NT release
  • thickest stereocilia = kinocilium (has thick ball at end)
  • tip links: when hair cells bend towards kinocolium it causes physical opening of gate which allows cations (K+) into cell –> depol = inc glu release –> top of short hair cell connected to sid of longer one
  • when it bends the other way it shuts the gate (hyperpol) –> closing and opening causes sound wave shape (sine)

adaptation: may have something to do with tip links, which are like spring coils (tight spring = easily open; loose spring = may stretch without opening = habituation)

34
Q

hair cells environment

  • top vs bottom
  • basal env
  • apical env
  • opening of channels results in?
  • active pumps
  • active zone
  • presynaptic dense body
  • presynaptic density
  • postsynaptic density
A
  • env around top of hair cells is diff than membrane potential around bottom of hair cells
  • basal env: perilymph has high Na+, low K+ (Vm = -45 to -60mV –> ~80mV more negative than endolymph)
  • apical env: scala media endolymph is K+ rich and Na+ poor (Vm = ~-125Vm)
  • opening of channels = influx K+ through top of hair cell = depol –> K+ does not want to be inside tho (high concentration of K+ inside)
  • VG ca++ channels open and vesicles release glu –> causes ligand gated calcium sensitive K+ channels at the base to open –> K+ exits
  • there are also VG K+ channels –> K+ leaves even faster
  • there are active pumps at the membrane border which pump the K+ back into the endolymph

active zone: unique area that has presynaptic dense body (electron rich) –> has vesicles tethered to outside –> keeps turning to let vesicles be released 1 by 1 (constant glu release)

  • presynaptic density has Ca++ channels that cause continuous glu release –> continuously stimulated at rest
  • postsynaptic density signals all the scaffolding proteins for the postsynapse

*only hair cells have presyn dense body/density/postsyn dense body

35
Q

cochlear nucleus

  1. medulla
    - tonotopic?
    - function
    - cochlea
    - cochlear nucleus
  2. pons
    - tonotopic?
    - superior olivary nuclei
    - MSO
    - LSO
  3. midbrain
    - tonotopic?
    - inferior col
    - projections (2)
    - superior col
    - visual inputs?
A
  1. medulla: tonotopic map; basic integration of auditory info with somatosensory system –> localization + must distinguish what sounds are coming from me and what sounds are coming from outside; integration of acoustic and somatosensory information
    cochlea: synapsing onto hair cells (leave cochlea through cranial nerve 8 - periphery)
    cochlear nucleus: nuclei of all the axons coming from the cochlea
  2. pons: no tonotopic map
    superior olivary nuclei: for localizing sound
    - medial superior olive: interaural timing difference –> where head is with respect to the sound (will hit one ear before the other)
    - lateral superior olive: interaural amplitude difference –> head casts a shadow –> high freq blocked by head
  3. midbrain: tonotopic map
    inferior colliculus: convergence of all ascending pathways (all auditory info from both ears); some of signal becomes subcortical projection to superior col - for fast automatic behaviours (eg. turning to a loud bang)
    - rest of projection to medial geniculate nucleus (thalamus) and then A1 (primary auditory cortex)
    superior colliculus: integrates LSO, MSO and cochlear nucleus info to localize and orient to sounds in 3D space
    - visual inputs too for reflexive orienting
36
Q

Primary auditory cortex

  • tonotopic organization
  • columnar organization (dominance)
  • higher processing
A
  • tonotopic organization: relevant sound occupy greater proportion of A1 (plastic - can change from person to person - we learn what is important)
  • columnar organization (neocortex): indiv columns respond to specific freq –> some columns respond to both ears, some have ear dominance
  • higher auditory regions respond to more complex sounds –> higher processing
37
Q

cortical blindness

  • what do they still have?
  • why?
  • pathway
  • awareness
A

has spatial awareness

  • eyes still seeing, ears still hearing
  • medulla has MSO and LSO - sound still reaching - continues to inf/sup colliculi - important in reflexive movement
  • they don’t know there’s still stimuli in env but they are still responding reflexively
38
Q

coincidence detectors

  • olives
  • ITD
  • location + absolute threshold
  • mapping
  • how do they function?
A
  • olives are responsible for sound localization
  • the time it takes to hit one ear is longer than the other (interaural timing diff)
  • located in MSO, can detect 1 degree diff in sound localization (~10us difference between ears = width of one finger)
  • maps the contralateral hemi – physical space of one side processed in opposite side of brain
  • the longer it takes for signal on right side to reach left ear, the longer time the right ear AP will have to hit more coincidence detectors –> detectors only activate if it gets signal from both sides
39
Q

spectral filtering

  • which body parts filter?
  • what is it for? (which plane)
  • study (what happened, what did they graph, results)
  • what happens when you deform the pinna?
A
  • ears, head and shoulders filter some frequencies and enhance others
  • the auditory system can use this info to help locate sound in the vertical plane

study: played white noise form diff places of env (white noise = all freq, like white light)
- graphed magnitude (dB) against freq
- depending on where sound is coming from, it is filtered differently (esp high freq) –> hit things/bounce off more

  • if you deform pinna ppl become worse at sound localization
40
Q

interoception

  • occurs where
  • sensory modalities
  • interoceptive sensations
A

interoception: the sense of the physiological condition of the body –> perception and integration of visceral signals
- occurs in the insular cortex

  • visual, hearing (audition), smell (olfaction), taste (gustation), touch (somatosensation), vestibular (balance); electroreception, magnetoreception, hydroreception
  • cardiac, respiratory, gastric, cutaneous (temp, itch, abrasion, social), sexual, urinary, chemo-humoral, soreness, bruise, stretching, pain
41
Q

subjective features of interoception

  1. quality
  2. spatial
  3. temporal

bidirectional
why is it important that info is processed in body too?

A

quality: don’t precisely know how ppl are feeling even if they describe it
spatial: vague locations of where you feel things
temporal: not a static perceptual quality –> comes and goes in waves

bidirectional: brain tells body what to do (eg. be nervous = sweat, heart rate inc, etc) but body also tells brain how ur feeling
- hard to ignore (very important!) –> some of the most important aspects are processed in the body because body needs to be involved in behaviour (needs to prepare for situation (eg. fight or flight)

42
Q

insula

  • posterior insula (activation intensity?)
  • anterior insula (correlated with, perception, feeling of __ )
A

posterior insula: supports psychophysical sensations (eg. how warm something is) –> graded activation along with temperature of stimulus, strength of touch
- intensity of stimuli predicts intensity of activation

anterior insula: subjective feelings (eg. how you feel about how cold something is) –> activity increased with how much they subjectively feel about stimulus

  • person who is super cold in lake has more activity than someone who doesn’t feel cold
  • correlated with maternal affiliation
  • perception of disgust in another person’s face
  • feeling like knowing (just on the tip of your tongue)
43
Q

clinical conditions

  • associated with what?
  • schizophrenia
  • depression
  • morals
A
  • every clinical condition is associated with altered interoception
  • the more grandiose someone feels (degree) is associated with accuracy in heartbeat detection (schizophrenia)
  • impaired facial disgust recognition in ppl with depression (reduced insular grey matter) –> decreased insula activation when processing positive emotional stimuli, increased when processing negative emotional stimuli
  • we also use bodily feelings to morally look at ppl (eg. feeling disgust/anger in your stomach)
44
Q

olfactory system

  • odors
  • receptor types
  • difference from other senses
A

odors: molecules in the air dissolve in the mucus of the olfactory epithelium (project cilia) and bind odorant receptors (mechanoreceptors – ligand-gated – open = depol) embedded in cilia of olfactory sensory neurons
- one receptor type can be bound by many different odorant molecules (with varying affinity)

difference from other senses: does not pass through thalamus – why smell gets so attached to memories and feelings (goes to reticular formation = automatic responses to horrible smells)

45
Q

olfactory pathway

  • where are neurons?
  • axons project where?
  • olfactory bulb neurons
  • olfactory cortex
  • chemotopic map
  • population code
A
  • olfactory sensory neurons scattered across the olfactory epithelium –> random/overlapping distribution of olfactory receptor mRNAs
  • axons project through the skull (cribriform plate) to specific glomeruli in the olfactory bulb
  • neurons of the olfactory bulb glomeruli project to the olfactory cortex (smell perception) and hippocampus (olfactory memory)
  • olfactory cortex neurons project to the hippocampus (learning and memory) + amygdala (emotional responses)
  • chemotopic map: olfactory bulb contains glomeruli where axons of olfactory sensory neurons with receptor types of same class project (has highly precise convergence!! –> specific receptor type olfactory sensory neurons onto indiv glomeruli)
  • indiv odorant activates multiple receptors = multiple glomeruli
  • pattern of activity across glomeruli (population code) –> unique for each odor

PSYC 370 (3 decks)

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