RAPID EYE-MOVEMENTS DENSITY AS A MEASURE OF SLEEP NEED - REM DENSITY DECREASES LINEARLY WITH THE REDUCTION OF PRIOR SLEEP DURATION

in the recovery nights from total and partial sleep deprivation there is a reduction of oculomotor activity during paradoxical sleep as comp ared to baseline nights. Aims of the present within-subjects study are to contribute in understanding the nature of the relationship between REM density and sleep need and to evaluate whether an inverse relatio nship exists between REM density and slow wave sleep (SWS) amount. Six healthy subjects were studied for 7 consecutive weeks with standard p olysomnographic recordings. Variations in REM density were assessed in the recovery nights following a gradual sleep restriction, obtained b y postponing the sleep onset time while maintaining the final awakenin g time constant. Results indicate that steep curtailment decreases REM density in the ensuing recovery nights; the decrease is linearly rela ted to the amount of sleep curtailment. The decrease in REM density pa rallels an increase in SWS, while no corresponding variation was found neither in the duration of paradoxical sleep nor in the latency of an y other sleep stage. These results suggest that REM density could be u sed as a measure of sleep need. Copyright (C) 1996 Elsevier Science ir eland Ltd.