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PSYC 367 > Quiz 2 > Flashcards

Quiz 2 Flashcards

1
Q

frequency coding

  • what happens during a “peak”?
  • high vs low freq
  • threshold tuning curve
  • outer hair cells
A

peak = when stereocilia bent the most = AP fired

  • peak occurs near oval window for high freq
  • near helicotrema for low freq
  • absolute threshold for indiv auditory nerve fibers as a function of frequency –> lowest threshold is at characteristic freq
  • outer hair cells improve sensitivity and frequency selectivity (sharpness of tuning curve –> respond to a narrower range of freq)
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2
Q

two-tone suppression

- frequency code

A

decrease in firing rate of auditory nerve fibre to its characteristic frequency when a 2nd tone of similar freq is presented at the same time
- frequency code for complex sounds is not the sum of individual AN fiber responses to indiv pure tones (complicates sensory coding)

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3
Q

isointensity curves

- curve represents what

A
  • curve = APs vs freq –> plot multiple intensities
  • there is a loss of frequency tuning in auditory nerve fibers at higher intensities (higher dB) –> curve flattens instead of having a sharp peak –> all neurons across the basilar membrane are responding
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4
Q

rate saturation

A

point at which an AN fiber is firing as rapidly as possible and further stimulation cant increase the firing rate
- AN nerve fibers fire faster for higher freq

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5
Q

phase locking

  • definition
  • above what freq do you need to use volley
  • what is the volley principle –> what freq
A

AN fibres fire at distinct point (phase) in cycle of sound wave –> provides a temporal code for sound wave freq
- at frequencies above 1000Hz AN fibers cant fire on every cycle
- volley principle: hypothesis that combining firing of a group of fibers matches freq of incoming sound (1000-4000Hz) to provide a temporal code for freq
(basically they take turns firing to get the right freq code)

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6
Q

sound frequency coding

  • 500-4000Hz
  • below 500Hz
  • above 4000Hz
A

500-4000Hz: both temporal (firing rate) and place (place of maximal firing) coding

below 500Hz: timing of firing in AN nerve (temporal = firing rate)
- can’t use place coding because the basilar membrane envelope is too broad for good freq discrimination –> no sharp envelope of activation

above 4000Hz: place of maximal firing on basilar membrane

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7
Q

high vs low spontaneous fibers

  • low
  • high
  • sound intensity coding (+ example)
A

low spontaneous fibers: high threshold, maximum rate above 60dB –> don’t fire when no sound is present, does not respond to low intensities –> only responds to high intensity sounds so it tells brain about changes in high intensities –> has thinner axons (spontaneous firing rate is related to axon diameter)

high spontaneous fibers: low threshold, maximum rate below 60dB –> codes intensity changes at low intensities –> saturates at high levels of sound –> cannot distinguish between high dB

sound intensity is coded by the number of fibers of each type firing
eg. the characteristic freq is 1200Hz, but a weak 1200Hz tone has a similar firing pattern to a strong 1400Hz tone since they are similar freq –> brain is able to tell the difference between a weak 1200Hz tone and a strong 1400Hz tone through high and low intensity fibers

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8
Q

intensity coding vs frequency coding

- how the graphs look different

A

Intensity: more AN fibers fire as sound intensity increases (curve gets bigger)

Frequency: AN fibers from diff regions of basilar membrane fire when intensity is constant but the frequency is changed (whole curve moves over)

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9
Q

ipsilateral vs contralateral

monaural vs binaural

A

ipsilateral: same side of body
contralateral: opposite sides of body

monaural: input from one ear
biaural: input from both ears

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10
Q

central auditory pathway

- SONIC MG (+2)

A

path goes from:

  1. cochlear nucleus: first synapse in auditory pathway
  2. SON: superior olive nucleus
  3. IC: inferior colliculus
  4. MG: medial geniculate nucleus
  5. auditory cortex (A1)
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11
Q

cochlear nuclei

  • cochlea connection
  • dorsal, posteroventral and anteroventral
  • monaural to biaural
A

cochlea to ipsilateral cochlear nucleus (3 subdivisions)

  1. dorsal cochlear nucleus: no synapse in SON
  2. posteroventral cochlear nucleus: synapse in CONTRALATERAL SON
  3. anteroventral cochlear nucleus: synapse in CONTRALATERAL OR IPSILATERAL SON

*note: until superior olive, everything is monaural –> crosses happen at SON –> becomes biaural –> need both ears to localize sound

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12
Q

inferior colliculus

  • SON
  • dorsal cochlear nucleus
  • medial geniculate nucleus
  • left and right
A
  • SON to ipsilateral inferior colliculus
  • dorsal cochlear nucleus to the contralateral AND ipsilateral inferior colliculus (bypasses SON)
  • inferior colliculus to ipsilateral MGN
  • connections between left and right inferior col.
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13
Q

medial geniculate nucleus

  • inferior col
  • A1
A
  • inferior col to ipsilateral MG

- MG to ipsilateral auditory core region (includes A1)

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14
Q

olivocochlear bundle

  • function (+speed?)
  • efferent fibers location + function
  • Ach release
A
  • suppress continuous background noise to make sounds easier to detect –> protects against damage from loud sounds (not fast tho, must go from ear to SON and back to ear)
  • efferent fibers are in the olivocochlear bundle –> control electromotility of outer hair cells –> innervate outer hair cells (come from SON) –> synapse with cochlea –> elongate and contract
  • Ach released by efferent –> decrease in [K+] = hyperpol = elongation
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15
Q

auditory cortex

  • location
  • auditory core region (3)
  • auditory association cortex (2)
  • tonotopic map
A
  • located in sylvian fissure (lateral nucleus)
  • auditory core region: includes A1, rostral core and rostrotemporal core

auditory association cortex:

  • Belt: inside sylvian fissure –> surrounds ACR
  • parabelt: can see from outside of brain; partially surrounds belt
  • tonotopic map: neurons that respond to diff freq are organized anatomically in order of freq (low CF = red, high CF = blue)
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16
Q

“where” pathway

“what” pathway

A

where: (aka dorsal) posterior parabelt to posterior parietal cortex to dorsolateral prefrontal cortex –> location
what: (aka ventral) anterior parabelt to orbitofrontal cortex –> pitch

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17
Q

audibility curve

  • most sensitive + why
  • standard threshold
  • base boost
A

absolute threshold for hearing as a function of frequency = sound pressure level that you can JUST detect

  • most sensitive from 2000-6000Hz –> pinna + auditory canal can amplify this range
  • @1000Hz –> STD amplitude threshold is around 0 dB (but we can hear below 0dB)
  • base boost: compensates for higher thresholds at high and low frequencies (without base boost, low pitch sounds will stop being heard first as loudness decreases)
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18
Q

hearing thresholds

  • audiometer
  • marking
  • staircase procedure
  • absolute threshold
  • high vs low freq
A

audiometer: instrument used to measure absolute threshold (dB) for pure tones of diff freq
1: yes
0: no
- staircase procedure: decrease by 10dB until they cant hear, inc by 5dB until they can hear –> find dB level where they can hear 4 times (the absolute threshold is between the lowest dB they can hear and the next level below it)
- at lower freq it is more noisy = need more trials to get overall dB level

19
Q

air vs bone conductance

- voice

A

air: cochlea stimulated (eg. headphones)
bone: vibration of skull
- your own voice is both air and bone conducted –> can hear low freq better –> ur voice in a recording is just air conduction

20
Q

loudness perception

  • confusion
  • diff SPLs; duration
  • matching task
  • phon
A

subjective impression of sound intensity (often confused with intensity or sound pressure level)
- diff sound pressure levels can result in the same perceptual experience –> increases with duration of sound

matching: adjust intensity of comparison tone to match loudness of standard tone with fixed intensity and freq
eg. 1000Hz 40dB –> adjust dB of 2000Hz tone to it

phon: unit of loudness for pure tones obtained from matching experiments
- sound that is 20 phon sounds the same as a 20 dB 1000Hz tone

21
Q

equal loudness contour

- examples

A

equal loudness contour: (for a single person) shows the sound pressure level necessary for comparison tones between 20 and 10,000Hz to achieve a match to the loudness of a 1000Hz standard tone of a fixed sound pressure level
(2 diff freq can sound the same if they’re on the same loudness contour, even if dB is diff; or 2 diff freq can sound diff if they’re on diff loudness contours even if they do have the same dB –> diff perception of SPL

22
Q

scaling

  • axes
  • unit of loudness
  • JND + webers law
A

if it was linear axes we would see a curve that levels off –> we use a power function with an exponent less than 1 (log log axes produces a line with a constant slope)
- loudness increases more slowly than intensity

sone: unit of loudness from a scaling experiment –> participants assign number to how loud diff SPLs seem to be (magnitude estimation) –> freq constant
- able to tell one sound is louder than the other (JND) requires 1-2dB change –> not a violation of webers law because dB scale is logarithmic! (increased intensity is still associated with an increase in sound pressure by louder amount to notice change)

23
Q

pitch discrimination

  • detection (range)
  • what causes the JND to increase in an experiment?
  • low freq?
A

detection: freq range of human hearing is 20Hz-20kHz (decreases with age)

JND increases as std freq increases
- we have good pitch discrimination at low freq (why place theory not fully correct)

24
Q

masking

  • measure
  • bandwidth
  • task
  • result
  • critical bandwidth example + explanation
  • general finding
A

measure absolute threshold for detecting pure tone in the presence of nice (sound contains a wide range of freq)

bandwidth: range of freq of masking noise
task: do you hear the tone in the first interval or the second?
result: harder to detect the tone as the noise bandwidth widens, but only up to a point (critical bandwidth = bandwidth beyond which adding more freq to the masking noise does not raise the absolute threshold anymore)
- critical bandwidth will be a DIFFERENCE
eg. CB = 400 Hz –> 1800 to 2200 Hz
- increasing the noise higher than 1800 will increase the absolute threshold (bad thing) until you pass 2200 then it won’t make a difference (max interference)

general finding: lower Hz test tones have smaller critical bandwidths
- CB = 1mm on basilar memb –> low freq (helic.) are more spread out than high freq (oval window) on basilar memb –> 1mm near helic contains a smaller range of freq than the 1mm near oval window –> therefore there is a smaller CB for lower freq because they are less spread out

25
Q

pitch perception

  • AN fiber selectivity
  • critical bandwidth
  • example
A

AN fibers have a characteristic freq and respond to a narrow range of freq –> critical bandwidth interpreted as revealing the freq tuning of sets of auditory neurons used to detect the test tone (selectivity)

  • freq outside the CB may stimulate a diff set of freq tuned neurons
    eg. if 800Hz is the CF, and CB is 400Hz, AN fiber will respond to 600-1000Hz tones, but 800Hz best (lowest absolute threshold at 800Hz)
26
Q

psychophysical tuning curves

  • task
  • result
  • effect on pitch perception
  • upward spread
  • when can both tones be heard?
A

task: can you hear the test tone during the masking tone
result: greatest masking effect when masking tone and test tone have same freq (need more intense masking tone when not same freq) –> sharper curve
- suggests pitch perception depends on place code
- upward spread of masking: masking effects when not same freq are asymmetrical –> masking freq lower than test tone are more effective
- must have 2 separate peaks on basilar membrane for both tones to be heard

27
Q

hearing loss types

  • conductive loss
  • sensorinerual loss (cochlear and auditory nerve)
  • presbycusis
A
  1. conductive: disturbance in mechanical transmission of sound through outer or middle ear
    - usually uniform loss at all freq, caused by injured ear drum, infections, or abnormal growth of ossicles
  2. sensorineural: cochlear or AN damage
    a) cochlear damage: decreased activity or injury of hair cells; usually restricted to certain freq, caused by infections, genetic diseases, ototoxic drugs, aging, exposure to sudden or prolonged loud sound
    b) retrocochlear dysfunction: damage to AN; often unilateral; often caused by tumors

2.1. presbycusis: usually sensorineural, usually bilateral, loss begins at high freq, but includes lower freq with advancing age; wearing out of hair cells (near oval window first = high freq)/degeneration of stria vascularis (lines middle canal, keeps endolymth healthy + ions balanced)

28
Q

hearing loss assessment

  • healthy ears
  • conductive loss
  • sensorineural loss
  • acoustic reflex threshold
A

healthy ears: cochlea stimulated by air or bone conducted sounds

conductive loss: can hear bone, not air
sensorineural: cannot hear bone and air –> doesn’t matter how sound is getting to inner ear since inner ear is the part that is the problem

acoustic reflex threshold: softest sound that elicits reflex is normally 70-100dB (pretty loud)
- having an elevated or absent reflex may occur with middle or inner ear damage/retrocochlear dysfunction

29
Q

ipsilateral vs contralateral reflexes

  • ipsilateral
  • contralateral
  • middle/inner ear problem
  • retrocochlear dysfunction
A

ipslateral reflex: right ear stimulation causes right reflex, left ear stimulation causes left reflex

contralateral reflex: right ear stimulation causes left reflex, left ear stimulation causes right reflex –> happens when signal crosses to opposite SON (facial nerve stimulates middle ear)

status of ipsilateral vs contralateral reflexes can indicate site of damage

eg. middle or inner ear problem: if ipsilateral reflexes are affected, so are contralateral (for damaged side)
- right inner ear damage causes abnormal right and left reflexes with right ear stimulation, but normal right/left reflexes with left ear stimulation

eg. retrocochlear dysfunction: different ipsilateral and contralateral reflex patterns
- right SON damage causes abnormal right and normal left reflex, with either right or left stimulation

30
Q

Hearing loss treatment

  • hearing aid (2 design components)
  • behind the ear
  • in the ear
  • bone anchored
  • surgery
  • cochlear implants
  • brainstem implant
  • future
A

hearing aid: for conductive or sensorineural loss –> amplifies sound pressure –> best with selective amplification for frequencies with greatest loss –> should keep high intensities at comfortable level

  • additional method is to move energy from frequency regions in which hearing is poor (usually high frequencies) into regions where hearing is normal (lower freq)
  • behind the ear: useful if some inner ear function remains
  • in the ear: good for mild to moderate hearing loss
  • bone anchored: surgically implated behind damaged ear –> used for conductive loss or severe unilateral sensorineural loss
  • surgery: conductive loss –> replace ossicles if immobilized; graft tympanic membrane
  • cochlear implants: severe sensorineural loss –> transforms sound into electrical signal –> electrode array stimulates AN fibers at appropriate positions along cochlea
  • brainstem implant: retrocochlear dysfunction –> electrical stimulation of auditory brainstem nuclei

future: sensorineural loss –> regeneration of hair cells (not yet in humans)

31
Q

hidden hearing loss

  • cause
  • hypothesis
A

exposure to high levels of noise can decrease your ability to use sound even when ability to detect sound remains normal (according to audiogram) –> caused by loss of synapses between AN fibers and hair cells (loss of connectivity
- hypothesized that this is why some ppl have difficulties listening in noisy situations (affects ability to understand speech or enjoy music)

32
Q

sound localization

  • azimuth
  • elevation
  • eg. left side path
  • ILD
  • largest vs no intensity difference
  • high vs low Hz waves
  • ITD
A

azimuth: left/right direction of sound source (straight ahead = 0 degree azimuth)
elevation: up/down position of sound source
eg. if path of sound is on the left, it will reach right ear with lower intensity (some sound will bounce off head)

ILD: interaural level differences –> only present at frequencies above 1000Hz (curves below are flat)

  • largest intensity differences occur when sound comes from directly left or right (90 degrees)
  • no intensity diff for sounds directly in front or behind (0 or 180)
  • high Hz sound waves bounce off head –> only some get to other ear
  • low Hz sound waves pass by head with no reflection

ITD: interaural time difference: if not directly in front or behind, there will be a difference in the moment that the sound wave reaches the ear (90 degrees = largest difference)

33
Q

superior olive

  • MSO
  • LSO
A
  • interaural info available in the superior olive
  • medial superior olive (MSO): neurons sensitive to ITD –> fire APs when stimulated by specific lag between L and R ear signals (small place differences on left and right basilar memb –> peaks happen at diff times)
  • lateral superior olive (LSO): neurons sensitive to ILD –> excitatory connections from ipsilateral ear, inhibitory connections from contralateral ear (inhib sent by MNTB to LSO) = results in extra excitation in one ear, and inhibition in the other ear
34
Q

cone of confusion

  • time differences
  • ILD
  • prediction
  • explanation (2)
A

interaural time differences for diff positions around the head –> every position in front of head has the same ITD as a position behind the head

  • ILD also are ambiguous
  • cone of confusion: predicts we should find it difficult to tell if sounds come from in front or behind us (but we don’t!)
  • able to tell because when we move our head horizontally, it changes the intensity and time differences = disambiguate location of stimulus
  • also able to tell because of the shape of our pinna –> unique –> different frequencies reflected from front and back (energy at eardrum not equally intense even tho it is equal at sound source)
35
Q

directional transfer function

A

DTF: shape of pinna and upper body change intensity of sounds w diff freq that arrive at each ear from diff locations in space
- sound from each aimuth and elevation has its down DTF; DTF diff for each subject too (diff pinna)

36
Q

vestibular sense

  • what is it for
  • semicircular canals (3)
  • otolith organs (2)
  • change in head motion (2)
  • change in position of head with respect to gravity
  • qualities of vestibular stimuli (2)
A

equilibrium

semicircular canals: anterior, posterior and horizontal
otolith organs: utricle (horizontal) and saccule (verticle)

change in head motion (acceleration)

  • semicircular canals - angulatory (rotary) acceleration
  • otolith organs - linear acceleration

change in position of head with respect to gravity
- otolith organs - tilt

qualities of vestibular stimuli: direction and amplitude

37
Q

vestibular sense - directionality

  • 3 planes
  • 3 axes
A

median (sagittal) plane: splits left and right
frontal (coronal) plane: splits front and back
transverse (axial) plane: splits top and bottom
x: points out front
y: points out left
z: points out top

38
Q

vestibular sense - rotation

  • roll
  • pitch
  • yaw
  • linear motion (3 axes)
  • tilt directions (3)
  • lying down?
A

roll: rotation around x axis (ear to shoulder)
pitch: rotation around y axis (forward)
yaw: rotation around the z axis (shake head no)

translation directions for linear motion:

  • backward and forward = x axis
  • sideways = y axis
  • up and down = z axis

tilt directions: (tilt = single move and stay there)

  • pitch = forward or backward
  • roll = left or right
  • no yaw tilt because there is no change in gravity for yaw
  • note: if you’re lying down and moving ur head there is no tilt bc no change in gravity
39
Q

rotary acceleration

  • path of stimulation
  • kinocilium
  • head rotation
  • towards vs away
  • receptor potential
A
  • stimulates receptors in the ampulla of each semicircular canal (ant, post, and horiz)
  • stimulates hair cells in the crista of the ampulla –> stereocilia of hair cells are embedded in cupula (jelly sheet)
  • longest stereocilia = kinocilium –> aligned so that all kinocilium point in same direction
  • head rotation causes endolymph to move in opposite direction –> cupula deflected, stereocilia bend toward kinocilium, neural signal (K+ channels open, causes depol –> excitatory –> releases glu into synapse with vestibular nerve fibers)
  • bending away from kinocilium = hyperpol (inhibitory –> channels close –> reduced glu = dec firing rate)
    receptor potential: graded; slow change in membrane voltage that is proportional to stereocilia bending
40
Q

direction coding - semicircular canals

  • maximal sensitivity axis
  • horizontal canal

pitch and roll

  • right vs left anterior canal
  • posterior canals
  • push pull response (right side, left side, firing rate)
  • amplitude coding
A
  • each semicircular canal is maximally sensitive around the axis that is perpendicular to it –> not sensitive to the other 2 axes
  • horizontal canal responds to vertical axis (z axis) –> therefore sensitive to yaw turns (horizontal canal forms a loop around z axis) –> very easy to study saw

pitch and roll: all 4 canals responsible

  • left and right anterior canals sensitive to same axis (oblique) but in opposite directions
  • same for posterior –> same axis but opposite directions

push-pull response: yaw motion to the right

  • right side: causes endolymph to move to the left; stereocilia bend toward kinocilium, depolarizes hair cells
  • left side: endolymph move left, stereocilia bend away from kinocilium, hyperpolarizes
  • firing rate increased in right vestibular nerve (excitatory), decrease in left vestibular nerve (inhibitory)

amplitude coding: one direction = how much above spontaneous rate; other direction = how much below spon level

41
Q

otolith organs

  • instead of ampulla
  • otolithic membrane
  • kinocilia arrangement (utricle vs saccule)
  • linear movement vs tilt
  • utricle –> which axes, which movements
  • saccule –> which axes, which movements
  • direction coding
  • amplitude coding
  • constant velocity
A
  • have macula instead of ampulla
  • stereocilia embedded in otolithic membrane (jelly)
  • kinocilia arranged towards striola in utricle and away from striola in saccule (striola divides each macula into 2 halves)
  • moving your hear forward/backward (linear) causes otocina (CaCO3 –> covers stereocilia embedded in otolithic membrane) to lag behind in opposite direction, but tilting causes them to go in same direction bc of gravity –> both cause stereocilia to bend = causes depol

utricle: horizontal –> sensitive to x and y axes linear acceleration; pitch and roll tilt
- cells on one side are sensitive to forward/backward,
saccule: vertical –> sensitive to x and z axes linear accel; pitch tilt

direction coding: tilt/linear accel in opposite directions cause opposite changes in firing rate
- tilt increases firing rate –> continues to respond whole time head is tilted –> on opposite side hair cells will be inhibited (push pull response)

amplitude coding: by firing rate –> higher for larger movements
- goes back to resting rate if it is at a constant velocity (reduction in response –> you stop feeling like youre turning)

42
Q

vestibular system dynamics

  • alcohol
  • oculogyral illusion
  • oculogravic illusion
A
  • alcohol changes density of endolymph; cupula deflects as it does when head is spinning
  • oculogyral illusion: visual disorientation and apparent movement following rapid body spins; cupula deflected in opposite direction before returning to resting state (why you feel dizzy after spinning –> otolith organs still doing stuff)
  • oculogravic illusion: apparent backward tilt and visual elevation experienced during forward body acceleration; macula cant distinguish between displacements due to horizontal acceleration or to static head tilt (why you feel like youre being pushed in an airplane before you start moving)
43
Q

judging distance

- 3 cues

A

cues:

  1. relative intensity: less intense with greater distance
    - simplest, but requires some assumptions
    - becomes useless when too far away –> inverse square law (intensity diff detectable only when close enough)
  2. spectral composition: further away = more “muddier” sound
    - high freq sounds decrease in energy more than low freq sounds because air dampens high freq more
    - only noticeable at far distances
  3. relative amounts of direct vs reverberant energy (close = mostly direct)
44
Q

echolocation

A

some blind people can make clicks with their mouths and use the returning echos to sense obstacles
- for an fMRI scan, the brain regions associated with vision of an blind echolocation expert light up (but not in a non-expert)

PSYC 367 (3 decks)

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