DYNAMIC FEATURES OF HEMODYNAMIC AND METABOLIC CHANGES IN THE HUMAN BRAIN DURING ALL-NIGHT SLEEP AS REVEALED BY NEAR-INFRARED SPECTROSCOPY

By the use of near-infrared spectroscopy, hemodynamic and metabolic ch anges were monitored continuously in the human brain during all-night sleep in a similar time dimension as closely monitored by electroencep halography. Measurements were started in the awake state, the values o f which were taken as the control. Contrary to what many have predicte d, the cerebral oxygen metabolic rate (CMRO(2)) increased during the t ransition from wakefulness to sleep. Cerebral blood flow (CBF) decreas ed during non-rapid eye movement (non-REM) sleep, in which a dissociat ion between changes in CBF and those in CMRO(2) was observed. The CBF returned to the control level even in response to the only 20-s appear ance of alpha activity on the electroencephalogram. During REM sleep b oth CBF and CMRO(2) were practically the same as the control level, wh ereas during the transition from REM sleep to arousal a disproportiona te increase in CBF compared with CMRO(2) was observed. Thus, it is sug gested that the flow-metabolic coupling mechanism is reset to a new le vel during sleep.