Hearing Science 1 Exam 2

Front 1

CN parts

Back 1

DCNVCN AVCN PVCN

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auditory pathway parts

Back 2

outer ear/middle ear/cochlea/auditory nerve/CN (DCN/VCN [AVCN/PVCN])/MNTB/SOC (LSO/MSO)/Lateral Lemniscus/Inferior colliculus/medial geniculate nucleus/auditory cortex

Front 3

DCN vs VCN

Back 3

DCN - spectral informationVCN - timing

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DCN

Back 4

spectral information. localization in elevation. projects IPSILATERALLY to LL and IC

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VCN

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Timing information. Projects CONTRALATERALLY to SOC and IPSILATERALLY.

Front 6

VCN parts

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Anteroventral CN (AVCN) - timing cues even more precise than in ANPosteroventral CN (PVCN) - coincidence detectors

Front 7

3 main CN cell types

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Bushy - AVCNOctopus - PVCNPyramidal - DCN

Front 8

explain the application of Parallel Processing in the auditory pathway

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AN fibers pass info through the CN. From the CN the info passes through multiple ascending pathways in PARALLEL which merge in the inferior colliculus

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Bushy Cells

Back 9

project to contralaterally and ipsilaterally to SOC. Participate in localizing sounds in the azimuth. Reproduce firing of primary afferent fibers (phase-lock). Mediate ITD at two ears in SOC.

Front 10

Octopus cells

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PVCN. Hyperpolarization (large conductance). DETECT COINCIDENCE of synchronous firing in populations of AN fibers. Compensate for the cochlear delay (traveling wave takes longer to reach apex/low frequencies).

Front 11

Coincidence detection

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Arrival of info from many neurons summed into one neuron. Input from many sharply tuned fibers with a wide range of CFs. Octopus cells convey the timing of the coincidence of those CFs with precision

Front 12

what would good OAE and cochlear microphonic but abnormal ABR mean?

Back 12

OHC are working. Something above that is not.

Front 13

fusiform/pyramidal cells

Back 13

detect spectral cues for localizing sounds in elevation (refines info from pinna). put spectral cues into context of position of head and ears. Project IPSILATERALLY to the IC.

Front 14

two pathways from CN (who what when where why)

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Monaural - "what" pathway, non-spatial info (spectral composition, temporal contrast, intensity) Binaural - "where" pathway, spatial info from both ears converges for localization

Front 15

how are frequencies in the CN tonotopically organized?

Back 15

all the way through it! low - ventrally and laterally, high - medially and dorsally

Front 16

where is the first site of binaural processing?

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SOC

Front 17

how is the SOC tonotopically organized?

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MSO - low frequency, code for timing differences, excitatory cells LSO - high frequency, code for intensity differences, excitatory AND inhibitory cells

Front 18

what cues localize sounds in the azimuth?

Back 18

ITDs and ILDs

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At what frequencies are we good at ITDs?

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Low frequencies - we are good at phase locking the low frequencies because of our innervation levels

Front 20

bilateral vs binaural

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bilateral - two ears working independently from each other - CIs

Binaural - two ears working together - NH

Front 21

binaural vs monaural

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Monaural - asymmetrical - the SNR is more positive in the non-masked ear. the maskers are to the side. the head shadow is the dominant monaural cue

binaural - symmetrical. the maskers are equal because the maskers are in both ears. ITD and ILD are the dominant binaural cues

Front 22

what decode spectral info and help with localizing in elevation?

Back 22

fusiform cells in the DNC

Front 23

which part of the SOC refines ILD?

Back 23

LSO

Front 24

which part of the SOC refines ITD?

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MSO

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MNTB

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Medial Nucleus of the trapezoid body. Relay station from CN to contralateral LSO - codes inhibitory information

Front 26

true or false: MSO receives both inhibitory and excitatory info.

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FALSE. That's the LSO. MSO gets only ipsilateral excitatory.

Front 27

binaural cue from ipsilateral excitatory inputs only

Back 27

ITD

Front 28

binarual cue from contralateral inhibitory AND ipsilateral excitatory inputs

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ILD

Front 29

describe how the HRTF would look for a sound coming from the -90 degree location

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the right ear would be lower (y-axis) and farther along on the x-axis than the left ear

Front 30

Describe the Duplex Theory

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ITD and ILD are processed by different mechanisms of the brain. ITD - MSO, low freq, excitatory only; ILD - LSO, high freq, excitatory AND inhibitory

Front 31

delay lines

Back 31

neural pathways to the coincidence detector

Front 32

when do the coincidence detectors fire maximally?

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when the neurons receive input from both ears

Front 33

describe how well humans localize in the horizontal plane

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1-2 degrees azimuth (10-20 microseconds). ITD range: 0 microseconds = directly in front. 700 microseconds = directly from the side

Front 34

describe the Jeffress model

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1. temporally-coded input signals consisting of spikes that are time-locked to the waveform of the acoustic stimulus,
2. two sets of tapped conduction delay lines that differentially delay these monaural neural patterns that are then fed into
3. an array of binaural spike coincidence detectors, whose outputs are then inputs into
4. coincidence counters that provide the number of coincidences as a function of relative delay.

IOW: Coincidence detection in the MSO. From each side axons (delay lines) meet. Depending on where they meet on the coincidence detector cells, we can localize a sound

Front 35

problems with the Jeffress model

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assumes that the MSO only responds to low frequencies (we think that the high frequency envelope can also code for ITD). doesn't account for inhibitory inputs either.

Front 36

explain the inputs in the LSO

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Excitatory - ipsi

inhibitory - contra

As the contra increases, the excitatory info becomes more refined. The inhibitory refines the excitatory (if it refines too much it cancels it out)

Front 37

binaural beats

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play two sounds within 30 Hz of each other (below 1000 Hz) one to each ear the brain integrates them to create a low frequency sound that's the difference between the two

Front 38

first site of parallel processing

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CN

Front 39

where is the Auditory Cortex

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deep in the Sylvian Fissure on the temporal lobe

Front 40

Auditory cortex organization

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bilateral projections (gets info from both sides). tonotopic organization is preserved in Heschl's gyrus in columns from low to high frequency moving anteriorly to posteriorly

Front 41

divisions of the AC

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Primary - Brodmann's area 41 and 42. Heschl's gyrus codes pitch info.

Secondary - complex rhythms and music

tertiary - gathers and combines info from primary and secondary

Front 42

how does the AC respond to sound?

Back 42

pretty much all the neurons respond. only those most preferred respond through the stimulus's duration (Middlebrooks)

Front 43

what would be the symptoms of an AC lesion?

Back 43

might hear and react reflexively, but there would be no meaning to the sound

Front 44

where is complex sound processed?

Back 44

Auditory Cortex

Front 45

attention

Back 45

attention enhances the neuronal response to a particular frequency. simply being told to listen to the noise makes the target voice seem quieter and vice versa

Front 46

name three peripheral auditory system objective measurements

Back 46

tympanometry, OAE, cochlear microphonic (the ABR set-up)

Front 47

name five central auditory system objective measurements

Back 47

ABR, fMRI, PET, CT, removal of auditory cortex in animals

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fMRI

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functional magnetic resonance imaging - measures blood flow to different areas. let's us assess if a person's AC has residual activity and therefore a CI candidate

Front 49

PET

Back 49

positron emission tomography. 3D image with poor resolution. complete stillness is unnecessary

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CT

Back 50

computed tomography

Front 51

describe the auditory organization in the brain

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left side more language focused.

Broca's area - frontal lobe

Wernicke's area - parietal lobe, lang dev and comprehension

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Wernicke's area

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fluent aphasia - fluent, even grammatical speech is possible, but it's confused and makes little sense.

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Broca's aphasia

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inability to speak in the presence of preserved language comprehension and vocalization

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top-down vs bottom-up

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central to peripheral - perception influenced by previous experience

peripheral to central - perception directs cognition

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neuroplasticity

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the ability of the brain to reorganize neural pathways based on new experiences

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bimodal hearing

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CI in one ear, HA in the other

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EAS

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electric and acoustic stimulation in the same ear

Front 58

relate otitis media and neural plasticity

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if chronic otitis media is left untreated throughout childhood, some of the auditory pathways might not be completely developed because they're not being used

Front 59

Hebbian theory

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neurons that fire together, wire together. Synapses between temporally coincident neurons are strengthened by the addition of receptors and neurotransmitters

Front 60

if [BLANK] has a lesion, behavioral plasticity cannot occur

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Auditory cortex

Front 61

Knudsen and OWLS

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barn owls had prisms put over their eyes. the auditory system eventually changed to match the modified visual signal.

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King et al

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ferrets --> juveniles with one plugged ear localized pretty well. initially, a plugged adult doesn't do well; they adapt eventually.

Front 63

critical period vs sensitive period

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critical period - limited time in which an organism can develop a skill under the influence of an external stimulus

sensitive period - similar, but less definitive end point. it takes more time and effort, but adaptation can happen

Front 64

talk about CI and NH kids hearing speech in noise

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as NH kids grow they get better on average naturally. as CI kids get older they don't get much better even training at least an hour a day, five days a week.

Front 65

Sharma et al.

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P1 - evoked response higher in the cortex (corresponds to speech perception). Associated with central maturation of the auditory system. The shorter the latency (the earlier CI was implanted), the more mature the auditory system. Basically, the earlier the implantation, the more normal the responses. the early implanted tend to be pretty normal while the late kids plateau