Gamma band EEG activity is enhanced after the occurrence of rapid eye movement during human REM sleep

This study investigated changes in gamma band (35-44 Hz) EEG activity associated with rapid eye movement (REM) during human REM sleep. Polysomnograms of eight healthy young volunteers were recorded during their normal nocturnal sleep using 26 scalp electrode sites. The recordings were analyzed for changes in gamma band EEG activity as a function of four sleep states (slow wave sleep, stage 2, tonic and phasic periods of the REM stage), electrode sites (six midline sites) and the time of occurrence (before and after rapid eye movement). The findings revealed that gamma band EEG activity is enhanced during REM sleep, particularly in the prefrontal regions during phasic periods of the REM stage, even after excluding the possible effects of peri-orbital activity. This result suggests that the prefrontal brain area is activated during the phasic periods of the REM stage. Moreover, results of this study show that the gamma band EEG activity is enhanced following the onset of REM. Taken together, these results suggest that enhancement of gamma band EEG activity is caused by processes such as ponto-geniculo-occipital activity, a lambda-like response and corollary discharge associated with REM.