Correlative changes of auditory nerve and microphonic potentials throughout sleep

Gross cochlear potentials in response to alternating clicks and pure tone bursts were recorded in guinea-pigs with chronically implanted electrodes in the round window during sleep and the awake state. A significant increase in both averaged potentials, the compound auditory nerve action potential (cAP) and cochlear microphonics (CM) occurred in slow wave sleep (SWS) with a subsequent diminution in paradoxical sleep (PS) periods. The cAP, CM, amplitude and area averages were similar during quiet wakefulness and in PS. Moreover, as an episode of PS progressed, the recorded potentials continued to decrease. On the other hand, increased averaged values were again observed during a subsequent episode of SWS. An involvement of the efferent olivo-cochlear bundle is postulated, first, because it is the only known pathway connecting the CNS and the auditory periphery and, second, because several key pre-receptor variables (middle ear muscles and ossicles and sound-source ear relation) were either abolished or altered dramatically.