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11/17
Hearing Sciences
| Question | Answer |
|---|---|
| Where do auditory evoked responses come from? | neural pathways and are conducted to rather distant electrodes through a complex media consisting of diverse substances, including fluids, brain tissue, bone, and skin |
| What are ABRs used for? | To detect pure tone thresholds and if there is a tumor on the brainstem pathway |
| What factors are involved in detecting volume conducted AERs? | the orientation of the electrodes to the electric field of dipole |
| What is a dipole? | a pair of equal and oppositely charged or magnetized poles separated by a distance |
| What is a near-field recording? | near the source (single unit recordings) |
| What is a far field recording? | relatively great distance from the source (auditory brainstem response) |
| Where are ethe generators (dipoles) of AERs located? | within the skull, either within the temporal bone of the cranium |
| What do Hall's (2007) recordings normally use? | far field techniques, with electrodes located outside of the skull usually at the scalp |
| What types of recordings did Hall (2007) use that were not far field? | intraoperative monitoring recordings from the 8th nerve or the ECochG when the electrode may be on the promontory |
| What is the promontory? | A big bulge on the cochlea |
| How can neurons be differentiated? | on the basis of structure of function |
| How can the neurons of the 8th nerve and pontine auditory brainstem be described? | at least five types, each with a distinctive appearance and response pattern |
| How can the major auditory stem nuclei be described> | structurally complex, each consisting of numerous sub-divisions |
| How many neurons and potential synapses between neurons are there? | 30,000 at the 8th nerve to 10 million at the auditory cortex |
| What are decussations? | midline crossings |
| How do the decussations of fiber tracts connect? | to the right and left sides of the brainstem and cortex |
| Where does the afferent auditory system have components? | within the reticular activating system |
| What does the efferent (descending) auditory system influence? | the function of the afferent (ascending) auditory system |
| What is the reticular activating system? | It controls the degrees of activity of the central nervous system as in maintaining sleep or wake |
| What does ECochG stand for? | electrocochleography |
| What does the ECochG consist of? | the cochlear microphonic, summating potential, and the compound 8th cranial nerve action potential |
| Where does the cochlear microphonic for Hall (2007)'s ECochG come from? | the outer hair cells |
| Where does the summating potential for Hall (2007)'s ECochG come from? | the inner hair cells |
| Where does the action potential for Hall (2007)'s ECochG come from? | the 8th nerve |
| What is the action potential component of Hall (2007)'s ECochG referred to as? | N1 for negative one, same at the ABR wave one |
| How can deflection of Hall (2007)'s ECochG be recorded? | with negative electrical polarity as opposed to a positive deflection found for the ABR wave one |
| What does the action potential of Hall (2007)'s ECochG Action potential reflect? | the synchronous firing of many 8th nerve fibers |
| How can Hall (2007)'s ECochG Action potential's amplitude be described? | the largest for transient stimuli |
| What is transient stimuli? | a click |
| Why are there overlaps on Hall (2007)'s ECochG? | to ensure that is it accurate |
| What happens to Hall (2007)'s ECochG as the stimulus level increases? | the action potential amplitude increases and latency decreases |
| Why does the action potential amplitude of Hall (2007)'s ECochG increase? | because of an increase in the number of 8th nerve fibers contributing to the response (there is more neuro-electrical activity summating at essentially the same time) |
| What is an increase in action potential amplitude of Hall (2007)'s ECochG related to? | an increase in stimulus level and an increase in the number of neurons that are stimulated |
| What is a decrease in latency do the action potential of Hall (2007)'s ECochG related to? | a more basal (high frequency) origin of cochlear activity |
| What is the second wave of Hall (2007)'s ECochG labeled? | N2 if negative, P2 if positive peak |
| When is ECochG used? | in patients with endolymphatic hydrops |
| What are endolymphatic hydrops? | abnormal fluctuations in the endolymph fluid, could lead to an increase in pressure int he endolymphatic system |
| What are the symptoms of endolymphatic hydrops? | feeling of pressure or fullness in the hears, hearing loss, tinnitus, balance problems, can lead to Meniere's disease |
| What is found in individuals with classic symptoms of Meniere's disease? | enlarged summating potential amplitudes |
| What does AD stand for? | right ear |
| What does AS stand for? | left ear |
| What are the two purposes of the auditory brainstem response? | to estimate pure tone thresholds with tonal tone-bursts or tone-pips and to some extent with click stimuli (test sounds) and also to determine the presence of an 8th nerve disorder |
| What is the importance of wave five in the auditory brainstem response? | it is the most prominent positive deflection in the ABR waveform and is most often used for clinical assessment of the ABR threshold because it is the only peak present near threshold |
| What is ABR? | auditory brainstem response |
| What is the latency of the normal ABR? | within 2 and 10 Ms after stimulation by a click stimulus |
| How is the ABR characterized? | by a series of six to seven waves |
| What did Hall (2007) say about the generator sites for the waves of ABR? | they are complex |
| What did Hall (2007) say about the first wave of the ABR? | it is the distal portion of the 8th nerve |
| What did Hall (2007) say about the second wave of the ABR? | it is the proximal portion of the 8th nerve |
| What did Hall (2007) say about the third wave of the ABR? | cochlear nucleus, second order neurons, approx 100,000 neurons innervated by 8th nerve, and superior olivary complex (ispilaterally) |
| What did Hall (2007) say about the fourth wave of the ABR? | multiple bilateral generator sites including the third order neurons located in the superior olivary complex |
| What did Hall (2007) say about the fifth wave of the ABR? | contralateral lateral lemniscus termination at the inferior Colliculus and direct pathways from the cochlear nucleus to the contralateral inferior colliculus |
| What did Katx et al (2009) say about the ABR? | it is not substantially influenced by attention or sleep which makes it optimal for evaluating patients who are unable or unwilling to cooperate such as infants or young children |
| What can affect an ABR? | core temperature, gender, and age |
| What happens to the ABR as core temperature decreases? | the ABR peak latencies increase with a decrease in amplidute |
| How do females' ABRs compare? | they have shorter response latencies and larger amplitudes that male due to a smaller cochlea |
| How do younger and older subjects' ABRs compare? | older subjects' have longer latencies and smaller amplitudes compared to younger, which could be related to hearing loss |
| How are infants' latencies compared to adults? | their peak latencies are longer |
| What is the effect of a stimulated high frequency hearing loss on the latency of the auditory brainstem response? | It would show up later on the ABR because the base hair cells are damaged, it takes longer for it to reach the next hair cells |
| Where is a click evoked ABR with highpass masking noise from? | a relatively low-frequency region of the basilar membrane |
| What can a highpass masker create? | a simulated high frequency hearing loss |
| How will the highpass masking noise conditions affect the ABR latencies? | It makes them much longer than on a normal audiogram |
| Why does the latency of the ABR increase as the highpass masking noise reaches lower frequency portions of the basilar membrane? | It takes a while for the traveling wave to move from the base to the apex |
Created by:
hrshook0104
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