AVS Reflexes and Evoked Potentials

Question 1

Is evoked spontaneous?

Answer 1

no, it needs something to stimulate it to get a response

Question 2

what are potentials?

Answer 2

measure voltage changes that we evoked by a sound
ex: receptor, resting membrane, action potentials

Question 3

How do we test our acoustic reflexes?

Answer 3

ART and reflex decay

Question 4

what frequencies do we test for ART

Answer 4

500 Hz, 1000 Hz, 2000 Hz, 4000 Hz

Question 5

What frequencies do we test for reflex decays

Answer 5

500 Hz, 1000 Hz

Question 6

what is the normal range for testing ARTs?

Answer 6

70-90 dB above pure tone AC threshold

Question 7

what are the reflexes for the vestibular system?

Answer 7

Vestibulo-ocular (eyes)
Vestibulocollic (neck)
Vestibulospinal (spinal cord)

Question 8

negative polarity at one end and a positive polarity at the other end

Answer 8

dipole

Question 9

Needle electrodes during a surgery

Answer 9

near field

Question 10

disc/surface electrodes in a clinical office

Answer 10

far field

Question 11

What are the cochlear microphonic?

Answer 11

alternating current potential that follows the waveform of the evoking stimulus
mimics the stimulus and AC looks like a sine wave
generated by the outer hair cells mainly (some contribution from IHC)

Question 12

What is summation potential

Answer 12

direct current produced in the cochlea in response to a sound
derived mainly from IHC but some OHC as well

Question 13

ABR wave I?

Answer 13

distal CN VIII (cochlea area of spiral ganglia)

Question 14

ABR wave II?

Answer 14

proximal CN VIII (Closer to BM) (approaching brainstem)

Question 15

ABR wave III?

Answer 15

cochlear nucleus

Question 16

ABR wave IV?

Answer 16

SOC

Question 17

ABR wave V?

Answer 17

LL / IC

Question 18

What does an ABR do?

Answer 18

measures absoute latency (where did it occur)
interpeak latency
amplitudes
amplitude ratio

Question 19

what is the largest and most stable wave of an ABR?

Answer 19

Wave V - IC and LL

Question 20

normal time at peak one of ABR

Answer 20

1.5 msec

Question 21

normal time between waves 1 and 5 in ABR

Answer 21

5.5 msec

Question 22

normal time at peak III of ABR

Answer 22

3.5 msec

Question 22

normal time at peak II of ABR

Answer 22

2.5 msec

Question 23

normal time at peak IV of ABR

Answer 23

4.5 msec

Question 24

normal time at peak V of ABR

Answer 24

5.5 msec

Question 25

what is the overall interpeak latency of waves I-V of ABR

Answer 25

4 msec

Question 26

What does wave I also represent?

Answer 26

compound action potential of ECochG

Question 27

What if the Wave I-III latency was normal and only the Wave III-V interpeak latency showed abnormalities?

Answer 27

would indicate a lesion in the CANS was higher than the cochlear nucleus region and can guide further testing and imaging

Question 28

what would we see if there is damage to the cochlear nucleus? Would we see a reflex arc?

Answer 28

pure tone hearing loss on the ispi side to damage. no reflex on ispi or contra

Question 29

why is important to have a variety of cells in the CN and responses from those cells?

Answer 29

auditory life would be boring if we only had octopus giving us onset responses (would world wouldn’t work well with communication or music if all we had was an onset responses and no other information and all we know is when it starts and that is it variety of cells for responses to have rich auditory environment captured that we live in think about only seeing one color

Question 30

What are response patterns in the CN?

Answer 30

rimary-like: initial spike and then steady response Chopper-on-off and on-off Onset-One initial spike and nothing else Pauser-similar to primary with a pause Build up—gradual increase

Question 31

excitatory neurotransmitters in CN

Answer 31

glutamate and aspartate

Question 32

inhibitory neurotransmitters in CN

Answer 32

GABA and glycine

Question 33

descending neurotransmitter in CN

Answer 33

Acetylcholine and noradrenaline

Question 34

what is the largest projection from the CN?

Answer 34

trapezoid body tract coming from AVCN

Question 35

Where are EE cells and what do they respond to

Answer 35

MSO and respond to phase differences (ITD)

Question 36

Where are EI cells and what do they respond to

Answer 36

LSO and respond to intensity differences (ILD)

Question 37

EE = excited by both ____

Answer 37

Contralateral & ipsilateral input

Question 38

EI =

Answer 38

excited contralateral and inhibited ipsilaterally

Question 39

IE =

Answer 39

excited Ipsilateral and inhibited contralateral

Question 40

if both ispi and contra are inhibited

Answer 40

II cell

Question 41

first letter describes

Answer 41

contralateral response (E or I)

Question 42

second letter describes

Answer 42

neurons response to sound in the ipsi ear

Question 43

why are pure tones not affected at the SOC?

Answer 43

they are already at the point of redundancy and enough gets through for a basic detection of the sound

Question 44

clinical significance in SOC

Answer 44

Pure tone thresholds not likely to be affected Localization can be affected Wave IV of ABR (some contribution to V) Contralateral acoustic reflex abnormalities, ipsilateral reflexes may be present Poorer performance on tests which rely on binuaral integration (Masking Level Difference and others)

Question 45

What is the cell type of LL

Answer 45

mainly multipolar globular cells with elongated neurons

Question 46

tonotopic organization of LL

Answer 46

lows dorsal highs ventral

Question 47

what part of LL is important for startle reflex?

Answer 47

VNLL

Question 48

where is the obligatory relay station of the ascending auditory pathway

Answer 48

inferior colliculus

Question 49

what relies on IC?

Answer 49

dichotic listening tasks and localization and orientation of the head

Question 50

what is sensitive to binaural stimuli and interaural differences

Answer 50

MGB and IC

Question 51

what is the hypothesis of the MGB

Answer 51

it begins the processing of speech

Question 52

tracts that run from the spinal cord and through the BS to cerebrum with many nuclei

Answer 52

RF

Question 53

what systems are conneCted to RF

Answer 53

auditory, sensory, motor

Question 54

what are the two divisions of RF

Answer 54

ascending reticular activation system and motor activation system

Question 55

what is our alarm or alerting system

Answer 55

ARAS of RF

Question 56

mechanism that helps with selective attention and listening in noise

Answer 56

ARAS of RF

Question 57

what is the main pathway from the MGB to the cerebrum

Answer 57

thalamocortical projections to cerebrum

Question 58

why is redundancy important

Answer 58

speech and communication in our rich environment have multiple ways for sound to get from cn 8 to cortex starts after leaving cn goes ipsi, contra and through commisures to the cortex

Question 59

what is the primary auditory area

Answer 59

heschl's gyrus

Question 60

is A1 planum temporale and the lateral fissure the same on both hemispheres?

Answer 60

no, larger on the left hemisphere where it is speech dominant

Question 61

receptive language processing area and spatial hearing area

Answer 61

planum temporale

Question 62

what is spatial hearing

Answer 62

in room with different noises and can close eyes and can tell where things are (ac or car going by) can visual or spatial map in mind by what you hear blind people hear in noise helps us maneuvar in the wosrld

Question 63

speech reception

Answer 63

wernickes

Question 64

expressive/motor

Answer 64

broca's

Question 65

associate words with images, sensations amnd ideas

Answer 65

angular gyrus

Question 66

what gyri integrate auditory somatic and visual info

Answer 66

wernickes brocas supramarginal and angular gyrus

Question 67

responsible for temporal sequencing of acoustic events

Answer 67

insula

Question 68

gray matter that is medial to the insula and sensitive to auditory info

Answer 68

claustram