Auditory Evoked Potential in Stage 2 and REM Sleep During a 30-Day Exposure to Tone Pulses

Ten subjects were exposed to 3.5K Hz tone pulses of 660 msec duration, presented 24-hr-per-day for 30 days. The interstimulus interval was 22 sec. There were 10 days each at 80, 85, and 90 dB in that order. The average evoked potential (AEP) at C₃ referenced to linked mastoids was obtained from contiguous stage 2 and REM sleep segments on the first, second, and last recorded nights of tone-pulse exposure. The AEP was consistently larger in stage 2 than in REM sleep. In both stage 2 and REM sleep, AEP amplitude on the second recorded night bore no consistent relationship to first or last recorded night AEPs. Only the N2–P3 amplitude yielded consistent decreases, with 9 of 10 subjects in both stage 2 and REM sleep having smaller N2–P3 amplitudes on the last than on the first recorded night. There were no changes in latency of any component. During sleep there is little, if any, habituation of the auditory AEP during long-duration exposures to nonmeaningful stimuli, and certainly no extinction of the AEP under these conditions.