SHORT BURSTS OF SLEEP-LIKE WAVES (MICROSLEEP) WERE FOUND IN EEG OF RATS ON A SLOWLY REVOLVING TREADMILL. IT WAS CONCLUDED THAT THIS SLEEP CONSISTED ONLY OF THE SLOW-WAVE SLEEP (SWS) PHASE, PARADOXICAL SLEEP (PS) BEING DIFFERENTIALLY DEPRIVED BY THE TREADMILL. IN A 2ND STUDY, SLEEP CYCLE WAS RECORDED BEFORE AND AFTER TOTAL SLEEP DEPRIVATION PRODUCED BY DEXTROAMPHETAMINE INJECTIONS, OR PS DEPRIVATION PRODUCED BY THE TREADMILL. THE SWS PHASE INCREASED ONLY FOLLOWING TOTAL SLEEP DEPRIVATION, WHILE A REBOUND INCREASE IN PS WAS PRODUCED BY PS DEPRIVATION AND BY TOTAL SLEEP DEPRIVATION. THE PS PHASE WAS INCREASED AS A PERCENTAGE OF TOTAL SLEEP BY BOTH TREATMENTS, SUGGESTING HIGHER PRIORITY FOR PS DURING PERIODS OF HEIGHTENED SLEEP NEED. (PsycINFO Database Record (c) 2006 APA, all rights reserved)