BERA

BERA


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Auditory brainstem responses (ABRs) recorded from electrodes placed on the scalp represent the far field of potentials generated by the fiber tracts and nuclei of the ascending auditory pathway between the cochlea and the brainstem. The ABR latency epoch consists of up to seven prominent wave peaks which appear within the first 10 ms. Commonly ABRs are elicited by transient stimuli (click, tone-burst, chirp). ABRs represent the sum of synchronized neural activity of the ascending auditory pathway. Wave I and II stem from auditory nerve, wave III from cochlear nucleus, wave IV and V from lateral lemniscus and inferior colliculus (brain stem), and wave VI and VII from sub-cortical regions. Due to the fact that the velocity of the traveling wave running into the cochlea is highest in the basal region, click-evoked ABRs mirror mainly the activity of basal (high-frequency) cochlear regions. This is also true for low frequency tone-bursts and chirps when high stimulus levels are applied. Wave V has the highest whereas wave I the lowest amplitude. Wave amplitudes decreases wave latencies increases with decreasing stimulus level.

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