Electrical activity of human limbic system during sleep

Visual analysis of 12 all-night depth recordings from two schizophrenic and six epileptic patients was compared to a previous study of chimpanzee sleep. Findings present in both human disease conditions and in normal chimpanzee include amygdaloid independence from cortical sleep staging, presence of a characteristic nonREM hippocampal waveform, and hippocampal preceding cortical flattening during arousal from stage 4 sleep. Some limbic sites in the human patients showed slow activity during REM and low voltage fast activity during stage 4. This last observation supports a sleep model which suggests that the differences in mental activity and in brain electrical activity during different sleep stages represent environmental surveillance by one portion of the brain during REM periods and by another during nonREM periods.