Tonic and Phasic Events during Sleep: Psychological Correlates and Implications

Abstract

The most widely accepted model of sleep in recent years has been one which draws qualitative distinctions between stage REM and NREM sleep. This conceptualization is now challenged by a tonic-phasic model which contrasts sleep periods of no phasic activation with those of phasic activation, regardless of their status on the REM-NREM dichotomy. This paper describes an experimental test of two hypotheses about sleep mentation based upon the tonic-phasic model: 1. phasic and nonphasic episodes within stage REM are associated with qualitatively different mental activity and 2. nonphasic stage REM is associated with mental activity qualitatively similar to that of NREM sleep. 10 Ss were studied for 4 nights each, with a grand total of 160 awakenings distributed among stage REM-phasic, stage REM-nonphasic, NREM sleep, and sleep onset. Analysis focused upon the last preawakening experience S could recall. Both hypotheses were supported: REM-phasic awakenings were associated with reports of Primary Visual Experience (PVE), REM-nonphasic and NREM awakenings with reports of Secondary Cognitive Elaboration (SCE), with sleep-onset awakenings intermediate in the incidence of PVE and SCE. Considerable discussion is devoted to some of the more general implications of the tonic-phasic model for the study of sleep and sleep mentation.