Intracranially recorded auditory nerve response in man. New interpretations of BSER

Compound action potentials were recorded from the intracranial part of the human auditory nerve when it was exposed during surgery with the use of a posterior fossa approach. Monopolar recordings of the response to tone bursts were dominated by a negative deflection that reached a peak 3 to 3.5 ms after the onset of a 5-ms 2-kHz tone burst. This negative peak matched the latency of the second vertex-negative peak of the scalp-recorded brainstem evoked responses (BSERs). Bipolar recordings from the intracranial part of the auditory nerve showed the biphasic waveshape that is typical for a nerve trunk. The results indicate that the neural generators not only of the peak in the BSER are likely to be located in the auditory nerve. Furthermore, the results indicate that it is the third wave that originates in the cochlear nucleus, not the second wave as was previously assumed.