REM sleep-associated hemoglobin oxygenation in the monkey forebrain studied using near-infrared spectrophotometry.

The oxygenation state of hemoglobin (Hb) in the monkey forebrain was monitored continuously throughout nocturnal sleep using a near-infrared spectrophotometric technique. During rapid eye movement (REM) sleep, an increase in oxygenated Hb occurred concomitantly with a decrease in deoxygenated Hb, while no significant changes in Hb oxygenation were observed during slow wave sleep (SWS). A gradual increase in total Hb content was also observed to occur during each REM sleep episode but not during SWS.