Sleep and the Visual Environment of Wakefulness : A Psychobiological Study

Abstract

A critical evaluation of the equivocal findings from previous sleep deprivation research revealed that a further study could be undertaken, taking into consideration, the quality of measurement adopted, the circadian variation and in particular, the context of sleep deprivation A theory of sleep in man, based upon biological premises and orientated towards the visual system was constructed. In order to provide a descriptive tool for sleep deprivation, a differential arousal schema incorporating the concept of controlled and controlling events, was evolved. A methodological study investigated the effects of high and low intensity input from the gross visual environment during 62 hours of sleep loss upon six male subjects. A three phase design incorporated into a latin square was used, with subjects undergoing oculomotor, cardiovascular, respiratory and performance measurement every six hours. All night sleep records were taken before and after sleep deprivation. The data were carefully analysed with respect to circadian variation and individual differences. The findings from the wakeful measures revealed that under the condition of high visual intensity, the untoward effects of sleep deprivation were substantially greater than for the. low intensity condition as reflected by heart rate variation, respiratory irregularity, binocular co-ordination and tracking performance. The findings with physiological data, in particular with cardiovascular measures, suggested that qualitative analysis was more likely to reveal the effects of sleep deprivation. The arousal schema was able to describe the sequence of changes exhibited by physiological and psychological data. A possible phase shift with the circadian variation of body temperature was seen to be of considerable importance. After the high intensity compared with the low intensity condition, recovery sleep data revealed significant increases in SWS and REM density, with decreases in REM. These findings provided support for the sleep theory. The binocular co-ordination measure appeared to be of potential use to sleep deprivation research, and a further study was undertaken with twelve subjects who underwent one night of sleep loss upon two occasions. Although all subjects showed a change in the predicted direction, this was significant with only half the subjects. A further small study to investigate the concept of oculomotor innervation for REM, provided somewhat obscure results which did not contradict the general sleep theory.