Computerized self-report sleepiness scales were administered before and after cognitive testing in a 72-hour sleep deprivation study. The cognitive test battery was administered every 2 hours and took approximately 1-1.25 hours. Two computerized measures of subjective sleepiness were used, one a visual analog scale, the other a Hebrew version of the Stanford sleepiness scale. The results indicated that both accumulated sleep loss, circadian and ultradian (2 cycles/day) factors were significant in determining subjective estimates of sleepiness. The extent of the differences between subjective sleepiness ratings before cognitive testing and after testing was dependent upon the phase of the circadian cycle. These differences were greatest at approximately 0200-0600 hours and least around 1000 hours. A second low point occurred at 1800-2000 hours. Analysis by complex demodulation of the individual subjects' sleepiness rating curves indicated that the amount of variance accounted for by the circadian component increased significantly after cognitive testing.

There are both monotonic and rhythmic factors in the patterns of change seen in physiological, psychological, and performance variables during sleep deprivation. These monotonic and rhythmic factors can be orthogonal, or they may interact with each other, with various task variables, or both. The importance of separating the rhythmic from the monotonic factors and of elucidating their interactions is discussed. Experimental methods and types of analysis appropriate to evaluating these factors are examined, with special emphasis on the complex demodulation time series analysis applied to group or individual subject data. The discussion is accompanied by data illustrations. It is suggested that sleep deprivation research should be designed so as to generate physiological and behavioral data that include information on both monotonic and rhythmic factors, the nature and extent of their interaction, and how they interrelate with systematically manipulated independent variables.

Three levels of working memory load of a visual search (Memory and Search) task were tested in a 72-hour sleep deprivation paradigm. General performance and accuracy decrease over time with monotonic and rhythmic components. The signal detection discriminability index, d', decreases monotonically with rhythmic variations. The index of response bias, β, shows no monotonic trend, but significant circadian rhythmicity. The extent of the monotonic and rhythmic changes in accuracy and in d’ is directly related to the level of working memory load. The amplitude of the circadian component of accuracy and d’ is enhanced for the higher levels of working memory load. The implication of potentiated circadian rhythmicity as a function of cumulative sleep loss is discussed.

No abstract

A series of four experiments, employing mice, investigated the generality of the learned helplessness phenomenon. The first two experiments used preexposure to aversive stimuli (shock), while the other two used preexposure to appetitive stimuli (food). In all of the studies, subjects were preexposed to contingent, noncontingent, or no stimuli (except for Experiment 2) in a Skinner box. During the test, animals preexposed to shock were tested with food, and those preexposed to food were tested with shock. The test was conducted in a similar situation, a Skinner box (Experiments 1, 3), or a different situation-a runway (Experiments 2, 4). Performance decrements were evident when subjects that were preexposed to a noncontingent stimulus were compared with subjects preexposed to contingent stimuli. The differences between the contingent and the noncontingent groups were significant, as were the differences between the contingent and the nonpreexposed groups (except for Experiment 1). The effects cut across the different types of stimuli, situations, and response requirements of the preexposure and test phases.