Allan Rechtschaffen

Mammalian Sleep, Longevity, and Energy Metabolism; pp. 425–446

Based on data for 53 mammalian species reported in the literature, statistical analyses revealed that daily sleep quotas correlate positively with metabolic rate and negatively with maximum life span

NOCTURNAL SLEEP OF NARCOLEPTICS.

Abstract The EEG patterns and eye movements of nine narcoleptics during nocturnal sleep were compared with those of normals. Seven of the nine narcoleptics showed a distinctive phenomenon which is virtually unknown in other pathological conditions or in normals. The narcoleptics had stage 1 rapid eye movement (REM) periods at sleep onset rather than approximately 90 min after sleep onset as most subjects do. This was interpreted as suggesting that narcoleptics are susceptible to “precocious triggering” of the pontine reticular formation. Other manifestations of narcoleptic sleep which distinguished it from that of normals were: (1) a superabundance of body movements; (2) the presence of 9–11 c/sec activity in anterior EEG leads; (3) a tendancy to have less than a normal amount of large slow wave activity.

Auditory awakening thresholds in REM and NREM sleep stages.

The auditory awakening thresholds of the major electroencephalographically defined sleep stages were compared. A modification of the method of constant stimuli was used in an apparently successful attempt to minimize the incorporation of the experimental stimuli into the mental activity of the sleeper. A total of 319 experimental trials were distributed among seven human Ss who served for about six experimental nights each. The sequence and timing of experimental trials were counterbalanced to control for nights, habituation, amount of accumulated sleep, and amount of sleep since last awakening. The results showed approximately equal awakening thresholds during REM periods (the rapid eye movement stage of sleep) and stage 2 (low voltage EEG and 12 to 14 cps “sleep spindles”). Both these stages had lower awakening thresholds than delta sleep (large slow EEG waves). Awakening thresholds became lower with accumulated sleep, independent of sleep stage. There were no significant stage independent relationships between awakening threshold and time since last awakening or time since last body movement, although the latter were varied over a relatively narrow range which limits the generality of these findings. There was no stage independent relationship between heart rate and awakening threshold. The possible physiological determinants of the awakening response were discussed.

Sleep deprivation in the rat by the disk-over-water method

Chronic sleep deprivation may be required to reveal the most serious physiological consequences of sleep loss, but it usually requires strong stimulation which can obscure the interpretation of effects. The disk-over-water method permits chronic sleep deprivation of rats with gentle physical stimulation that can be equally applied to yoked control rats. A series of studies with this method has revealed little or no pathology in the control rats. The deprived rats show a reliable syndrome that includes temperature changes (which vary with the sleep stages that are lost); heat seeking behavior; increased food intake; weight loss; increased metabolic rate; increased plasma norepinephrine; decreased plasma thyroxine; an increased triiodothyronine-thyroxine ratio; and an increase of an enzyme which mediates thermogenesis by brown adipose tissue. The temperature changes are attributable to excessive heat loss and an elevated thermoregulatory setpoint, both of which increase thermoregulatory load, and the other changes are interpretable as responses to this increased load. This pattern indicates that sleep serves a thermoregulatory function in the rat. The sleep deprived rats also show stereotypic ulcerative and hyperkeratotic lesions localized to the tail and plantar surfaces of the paws, and they die within a matter of weeks; the mediation of these changes is unresolved.

Suprachiasmatic nuclei lesions eliminate circadian temperature and sleep rhythms in the rat

We conducted a long-term study of the circadian rhythms of temperature and sleep in the rat after lesions of the suprachiasmatic nuclei (SCN). Brain temperature was measured with thermistors and sleep-wake was scored on the basis of continuously recorded EEG using a computerized system. Rats with complete SCN lesions did not exhibit circadian rhythms in constant dim illumination. Rats with partial SCN lesions generated weak and variable free-running rhythms, and when exposed to a light-dark cycle, some showed a reduced amplitude and altered waveform relative to normal rats. A few rats with partial SCN lesions showed a recovery of function. There was little difference between the circadian rhythms in temperature and waking, and these measures responded similarly to all lesions. Thus, no support was found for the notions that anatomically distinct oscillators control the circadian rhythms of temperature and activity, or that an oscillator outside of the SCN controls the circadian rhythm of temperature.

The effect of amphetamine on the sleep cycle

Abstract The administration of d-amphetamine sulphate to eight subjects before they went to bed resulted in a significant decrease in the percentage of sleep time spent in REM periods (the rapid eye movement, low voltage EEG stage of sleep) as compared with nights on which no drugs were given. Similarly, the administration of a combination of amphetamine and pentobarbital to seven subjects before they went to bed resulted in a significant decrease in percentage REM period time as compared with nights on which pentobarbital alone was administered. The administration of amphetamine and pentobarbital to three subjects for three or four consecutive nights produced percentage REM period times below their normal values. Upon withdrawal of the drugs, these subjects showed apparently compensatory increases in percentage REM period time above their normal values.

Sleep Deprivation in the Rat: IV. Paradoxical Sleep Deprivation

Twelve rats were subjected to paradoxical sleep deprivation (PSD) by the disk apparatus. All PSD rats died or were sacrificed when death seemed imminent within 16-54 days. No anatomical cause of death was identified. All PSD rats showed a debilitated appearance, lesions on their tails and paws, and weight loss in spite of increased food intake. Their yoked control (PSC) rats remained healthy. Since dehydration was ruled out and several measures indicated normal or accelerated use of nutrients, the food-weight changes in PSD rats were attributed to increased energy expenditure (EE). The measurement of EE, based upon caloric value of food, weight, and wastes, indicated that all PSD rats increased EE, with mean levels reaching more than twice baseline values. All of these changes had been observed in rats deprived totally of sleep; the major difference was that they developed more slowly in PSD rats.

Circadian temperature and wake rhythms of rats exposed to prolonged continuous illumination

The purpose of this study was to simultaneously measure temperature and sleep in the rat under continuous illumination in an attempt to reveal properties of the underlying circadian oscillators. At first, the circadian rhythms of temperature and wake free-ran in parallel. Within weeks or months, circadian arrhythmicity developed in most animals. Both circadian rhythms eventually damped out, even at fairly low light intensities. The circadian rhythm of wake was weaker and disintegrated sooner than the circadian rhythm of temperature. Although the data did not rule out control by separate circadian oscillators, one for temperature and one for wake, a single oscillator model was sufficient to explain this phenomenon. Ultradian variations with a period of about 2-5 hr were superimposed upon the circadian rhythms. When the circadian rhythms damped out, the ultradian variations remained. The ultradian bursts of wake preceded the ultradian bursts of temperature, suggesting a causal relationship. On the other hand, the circadian rhythm of temperature could not be dependent on the circadian rhythm of wakefulness, because the temperature rhythm could persist while the wake rhythm was absent.

Amount of Dreaming: Effect of Incentive, Adaptation to Laboratory, and Individual Differences:

The relationships between several variables and amount of dreaming, defined as time spent in the rapid eye movement stage of sleep, were investigated. Twenty Ss slept in the laboratory for four nights each in accord with a counterbalanced design. Monetary incentive to control amount of dreaming had a small but significant effect on amount of dreaming. On the first experimental night, Ss dreamed less than on succeeding nights; this decrease in dreaming was associated with more spontaneous awakenings on the first night than on succeeding nights. There were stable individual differences in amount of dreaming. The longer the sleep period prior to the first dream of the night, the longer was the first dream.

PRESLEEP DETERMINANTS OF DREAM CONTENT: EFFECTS OF TWO FILMS

Twenty-four Ss were exposed to controlled presleep stimuli. On one experimental night, they saw a violent episode, on the other, a nonviolent episode, from a TV western series. Dreams were collected using Dement and Kleitmans electrophysiological methods, by means of which rapid eye movement (REM) periods were used to identify “dream” periods. REM reports following the violent episode were longer, and more imaginative, vivid, and emotional, but neither more unpleasant nor more violent, than those following the nonviolent film. Direct incorporation of the content of either film was very infrequent. It was also shown that MMPI clinical scales correlated positively with ratings of many “dream-like” features of sleep mentation, and that, although there were stylistic similarities between waking and sleeping fantasy, there was little similarity in instinctual content. Finally, recent findings on the extent and nature of sleep mentation occurring outside REM periods were almost totally confirmed.