An investigation of the auditory frequency-following responses as compared to cochlear potentials

Comparisons were made of cochlear microphonics (CM) and scalp recorded frequency-following responses (FFR) from chinchilla and human. The latency of the scalp/ear-lobe recorded FFR was found to be nearly zero with respect to CM. Further, auditory nerve action potential were noted to diminish rapidly after death whereas the CM component in FFR reduced gradually. The decay of the CM component of FFR measured at the scalp after death followed an identical time course to that of the CM at round window. These observation lead to the conclusion that FFR does not originate in the brain stem but is essentially cochlear potentials picked up by electrodes located at the scalp.