B-4. Neurophysiology of sleep in humans

Abstract

Studies on EEG slowing in the progression of sleep since the discovery of electroencephalogram (EEG) in the 1920s, and identification of rapid eye movement (REM) sleep in the 1950s lead to the current principle that human sleep consists of REM and non-REM (NREM) sleep cycles. In this lecture, I will review sleep-wake homeostasis. Quantitative analysis of sleep EEG has revealed that delta EEG activity is enhanced according to the length of prior wakefulness, and achieved the recovery of the brain. This provides understanding on those clinical facts that disturbed sleep accelerates physical or mental disorders. I will also review a recent topic that deep NREM sleep with delta EEG activity is an active brain process, in which memory and skills acquired during wakefulness are consolidated and made to be ready for use. In addition, such delta EEG activity during sleep is more strongly induced in those cortical areas where intensive task is loaded during wakefulness. Finally, I will consider how the above processes are controlled by the network between the thalamus and the cortex, with special reference to its relation to conventional sleep EEG patterns such as K-complex, spindle or sleep delta waves.