Comparison of the event-related potentials between tonic and phasic periods of rapid eye movement sleep.

The event-related potentials (ERP) of eight young healthy volunteers were recorded during wakefulness and rapid eye movement (REM) sleep using an auditory discrimination task. REM sleep was classified into phasic and tonic periods according to the presence or absence of REM. In wakefulness, deviant stimuli elicited a P300 that was maximal over parieto-central areas. During the tonic period of REM sleep, deviant stimuli elicited a P200 and a P400. The P200 was distributed more anteriorly and the P400 was distributed more posteriorly than the P300; however, no prominent ERP components were observed during the phasic period. The study's findings suggest that the brain is less sensitive to external stimuli during the phasic period than during the tonic period of REM sleep.