The Stanford Sleepiness Scale (SSS) is a self‐rating scale which is used to quantify progressive steps in sleepiness. The present study investigated whether the SSS cross‐validates with performance on mental tasks and whether the SSS demonstrates changes in sleepiness with sleep loss. Five college student Ss were given a brief test of memory and the Wilkinson Addition Test in 2 test sessions and The Wilkinson Vigilance Test in 2 other sessions spaced throughout a 16‐hr day for 6 days. Ss made SSS ratings every 15 min during their waking activities. On night 4, Ss underwent all night sleep deprivation. On all other nights, Ss were allowed only 8 hrs in bed. Mean SSS ratings correlated r= .68 with performance on the Wilkinson Tests. Discrete SSS ratings correlated r= .47 with performance on the memory test. Moreover, mean baseline SSS ratings were found to be significantly lower than corresponding ratings of the deprivation period.

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Whereas respiratory rhythm, heart rate, and blood pressure tend to be basal in NREM sleep, they display greater activity and greater variability during REM phases (3-5, 11, 12, 31). The fine muscles of the face and extremities contract frequently, though there are few gross body displacements (14). In the absence of movement, however, muscle tone measured from the head and neck virtually disappears in REM periods (20, 32). The extrinsic ocular muscles are an exception to this rule. Before and during shifts of eyeball position, tone may be sustained in uninvolved and antagonist muscles (33). Penile erections are specific to the REM periods, detumescence occurring as NREM sleep ensues (34). Basal skin resistance, which should fall with heightened arousal, has been reported to rise in REM sleep by some investigators (35) but not by others (11, 30). In view of the eye activity and oneiric phenomena during REM sleep, it is intriguing that the REM sleep EEG is remarkably similar to that of a subject awake under circumstances of visual imaging or stimulation, when alpha activity is blocked. Furthermore, cortical responses evoked during the waking state are extremely similar to those evoked in REM sleep (36).An unexpected finding has been that motor-response and arousal thresholds are no higher in deep NREM sleep than in REM sleep (5, 37). This seems to fit with the finding in cats that during REM sleep there is a high response threshold in the mesencephalic reticular formation to auditory (38) as well as to direct stimulation (39, 40). In spite of the lowered responsiveness to stimulation, however, there is greater spontaneous activity in the reticular formation during REM sleep (39). (It is precisely this aspect of brain functioning in REM sleep which renders "depth of sleep" so difficult to designate.) Huttenlocher has speculated that in REM sleep evoked responses may be occluded because of this high level of spontaneous activity. Recently, however, Adey et al. (41) were not able to demonstrate higher response thresholds in the mesencephalic reticular formations of chimpanzees during REM sleep. Studies in AnimalsA dual neurophysiological organization of sleep is not specific to human beings. Every species of mammal so 29 APRIL 1966 far studied exhibits rhythmically alternating periods of REM and NREM activity which are marked by vegetative alterations similar in most respects to those that are found in man (12, 41-52).Moreover, animal experimentation has greatly extended our knowledge of the active processes occurring in the central nervous system during the REM state, such as: increase in blood flow to the cortex (47); rise in brain temperature (52); elevation in frequency of spontaneous neuronal firing in the MRF (39), medial and descending vestibular nuclei (53), pyramidal tract (54, 55), and occipital cortex (56); development of monophasic wave aggregates in the pons, lateral geniculate body, and other subcortical areas; continuous theta activity in the hippocampus (even more regular than during arousal) (9, 51...

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Improvements in specific measures of basketball performance after sleep extension indicate that optimal sleep is likely beneficial in reaching peak athletic performance.

Sleep and wakefulness are governed by both the suprachiasmatic nuclei of the hypothalamus (SCN), and a sleep homeostatic process; however, the interaction of these control systems is not well understood. From rodent studies it has been assumed that the SCN promote neither wake nor sleep but gate the homeostatic sleep-promoting process. Yet in humans sleep tendency is lowest during the later waking hours of the day, and sleep duration can be predicted because of the precise circadian timing of waking. Thus in primates, the SCN could assure sleep-wake cycle consolidation by actively promoting or facilitating wakefulness. To evaluate this hypothesis, we examined the sleep-wake and sleep-stage patterns of intact and SCN-lesioned (SCNx) squirrel monkeys maintained in constant light. This diurnal primate has consolidated sleep and wake patterns more similar to man than rodents. Sleep-wake, sleep stages, brain temperature, and drinking circadian rhythms were eliminated, and total sleep time was significantly increased (4.0 hr, P < 0.01) in SCNx monkeys. However, total times in deeper stages of non-rapid eye movement (non-REM; e.g., delta sleep) and REM sleep were not significantly affected by SCN lesions. Increased total sleep time was associated with a reduction in subjective day wake consolidation, as evidenced by substantially shorter wake bout lengths in SCNx monkeys (15 +/- 6 min) as compared to intact monkeys (223 +/- 10 min; P < 0.0001, ANOVA). These findings show that the SCN influence the regulation of daily total wake and sleep times, and implicate an alternative sleep-wake regulatory model in which an SCN-dependent process actively facilitates the initiation and maintenance of wakefulness and opposes homeostatic sleep tendency during the subjective day in diurnal primates.