Sleep deprivation and naps

It is important for military commanders to know the likely effects of a small amount of sleep under conditions of sustained operations. To this end, two laboratory-based experiments on naps were carried out. The first examined the effect of 2 h of sleep following 90 h of wakefulness. Ten infantrymen subjects were not told the scheduled length of their vigil, or that they would be allowed a nap at some stage, until a few hours before the 2-h nap. After 3 nights without sleep, the subjects’ average cognitive performance was 55% of the control values. During a test session immediately before the 2-h nap, performance improved by 30%, to 85% of control values, indicating the considerable effect that the incentive of knowing that a nap is imminent can have on even severely sleep-deprived subjects. In the second experiment, two groups, each of six infantrymen, took part in a 5-day trial; for one group, 4 h of uninterrupted sleep was scheduled and for the other, four l-h naps in each 24-h period. There were no significant differences in cognitive test scores or mood between the two groups. On the last experimental day, cognitive test and mood scores were not significantly different from baseline values for either group, indicating the utility of 4 h of sleep, either in one uninterrupted block or in four scheduled 1-h naps per 24 h.     

Experiments on extended performance: Repetition,age, and limited sleep periods

Four experiments on the effects on performance of extended time periods without sleep and on the effects of limited sleep, that is, naps, within such periods are reviewed. The performance measures included subjective measures and measures of performance on attention/persistence, continuous-production, precision, and cognitive tasks. Repeated periods of sleep deprivation did not result in decreased effects: Older subjects tended to be more vulnerable to sleep-loss decrements, and three different schedules of 4 h of sleep within a 60-h sleep-deprivation period had limited differential ameliorative effects.     

An Experimental Investigation of the Effects of Acute Sleep Deprivation on Panic-Relevant Biological Challenge Responding

Prospective research indicates sleep deprivation potentiates anxiety development, yet relatively little research has examined the effects of sleep deprivation in terms of specific types of anxiety. The current study tested the association between acute sleep deprivation and panic-relevant biological challenge responding among nonclinical participants. One hundred and two participants were randomly assigned to either an experimental (acute sleep deprivation) or control (no sleep deprivation) group. The day prior to and following the experimental (sleep) manipulation, participants completed a 5-minute 10% carbon dioxide–enriched air laboratory-based biological challenge. As predicted, sleep deprivation increased anxious and fearful responding to the challenge. Findings suggest sleep deprivation may be an important factor to consider in models of panic development. There are several areas in this general domain that warrant additional investigation.     

The structure of mood: A comparison between sleep deprivation and normal wakefulness conditions

The stability of the factor structure of mood was examined under two different experimental conditions, sleep deprivation and normal wakefulness In the first phase of the study, two different forms of a mood scale were administered to several college classes, and the ratings for each scale were intercorrelated and factored Eight interpretable factors emerged from each analysis, and the two sets of factors were highly congruent. In the second phase of the study subjects completed the mood ratings after staying awake all night or after getting a good night's rest Comparisons between the means for the two groups showed significant differences on 26 of the 44 variables included in the scale The scores for the sleep-deprived group were then intercorrelated and factored, and the factor structure was compared with the relevant factor structure obtained in the first phase of the study The results of the comparison showed that six of the eight factors appeared under both conditions of sleep deprivation and normal wakefulness Additional analysis indicated that a seventh factor appeared, but in the guise of different variables The only factor which failed to appear under sleep deprivation was elation. It was concluded that although variable ratings showed high sensitivity to the experimental operations, the basic structure of the underlying mood states remained remarkably stable The results indicate that the search for a list of basic mood states may be quite fruitful An important methodological implication was that a variable may be selected to measure a mood under various experimental operations with the assurance that the nature of the mood to be measured does not change as a result of those operations     

Effects of sleep deprivation on auditory and visual memory tasks

Probe recognition tasks have shown the effects of sleep deprivation following a full night of sleep loss. The current study investigated shorter durations of deprivation by testing 11 subjects for accuracy and response time every 2 hr. from 10 p.m. through 8 a.m. We replicated Elkin and Murray's auditory single-probe recognition task using the number triplets and added two visual tasks with number and shape triplets. Series of six stimuli were each followed by a probe, which was presented after 2.5 sec. as a short delay or 20 sec. as a long delay. Accuracy performance showed a significant decrease for the long delay beginning after 4 a.m. for the two visual tasks. Response times were significantly slower for the visual shapes task using the short delay. Visual tasks, especially shapes, may be more prone to disruption by sleep deprivation, given the visual information load and the briefness of iconic memory.     

3-minute smartphone-based and tablet-based psychomotor vigilance tests for the assessment of reduced alertness due to sleep deprivation

The psychomotor vigilance test (PVT) is widely used to measure reduced alertness due to sleep loss. Here, two newly developed, 3-min versions of the psychomotor vigilance test, one smartphone-based and the other tablet-based, were validated against a conventional 10-min laptop-based PVT. Sixteen healthy participants (ages 22–40; seven males, nine females) completed a laboratory study, which included a practice and a baseline day, a 38-h total sleep deprivation (TSD) period, and a recovery day, during which they performed the three different versions of the PVT every 3 h. For each version of the PVT, the number of lapses, mean response time (RT), and number of false starts showed statistically significant changes across the sleep deprivation and recovery days. The number of lapses on the laptop was significantly correlated with the numbers of lapses on the smartphone and tablet. The mean RTs were generally faster on the smartphone and tablet than on the laptop. All three versions of the PVT exhibited a time-on-task effect in RTs, modulated by time awake and time of day. False starts were relatively rare on all three PVTs. For the number of lapses, the effect sizes across 38 h of TSD were large for the laptop PVT and medium for the smartphone and tablet PVTs. These results indicate that the 3-min smartphone and tablet PVTs are valid instruments for measuring reduced alertness due to sleep deprivation and restored alertness following recovery sleep. The results also indicate that the loss of sensitivity on the 3-min PVTs may be mitigated by modifying the threshold defining lapses.     

A comparison of continuous and distributed reduced sleep schedules

After a night of normal sleep, 36 subjects were divided into three groups of 12. One group was allowed to continue sleeping normally, one group had four hours continuous sleep and the third group had three 80-min periods of sleep distributed throughout the 24-h period, for the next four days. Subjects were given a visual vigilance test on each day. Overall performance was rather better following distributed than following continuous reduced sleep, but rather worse than following 8 h of sleep. The main difference between the reduced sleep groups was in their decision criterion. It was suggested that this difference mainly reflected the difference in time since the two groups had last slept.     

Effects of sleep deprivation on cognitive performance by United States Air Force pilots

This study examined the effects of 35 h of continuous sleep deprivation on performance in a variety of cognitive tasks as well as simulated flight. Ten United States Air Force pilots completed the Multi-Attribute Task Battery (MATB), Psychomotor Vigilance Task (PVT), and Operation Span Task (OSPAN), as well as simulated flight at 3 h intervals over a 35 h sleep deprivation period. Performance declined on all tests after about 18–20 h of continuous sleep deprivation, although the degree to which performance degraded varied. During the second half of the sleep deprivation period, performance on the simulated flight was predicted by PVT and OSPAN reasonably well but much less so by the MATB. Variance from optimal flight performance was predicted by both PVT and OSPAN but each measure added incremental validity to the prediction. The two measures together accounted for 58% of the variance in flight performance in the second half of the sleep deprivation period.     

Dynamic changes in work/rest duty cycles in a study of sleep deprivation

The effects of moderate workload and 72 h of sleep deprivation were studied using a modified continuous-performance paradigm. Ten subjects were tested hourly on a number of perceptual and cognitive tasks designed to require approximately 30 min to complete, with the remainder of each hour free. As sleep deprivation continued, the average time on task increased at an accelerating rate. The rate of increase differed among tasks, with longer tasks showing greater absolute and relative increases than shorter ones. Such increases confound sleep deprivation and workload effects. In this paper, we compare the advantages and disadvantages of several experimental paradigms; describe details of the present design; and discuss methodological problems associated with separating the interactions of sleep deprivation, workload, and circadian variation with performance.     

Facilitation of the effect testosterone on male sexual behavior in rats deprived of REM sleep

The possibility of rapid eye movement sleep deprivation (REMd) altering the effect of testosterone on masculine sexual behavior was investigated. Adult castrated male Wistar rats with no sexual experience were randomly assigned to the following three groups: REMd (using the water tank technique) for 7 days, large platform control for 7 days, and undisturbed sleep control. All subjects were treated with 1 mg testosterone propionate daily for 14 days. Masculine sexual behavior was assessed 3 consecutive days prior to steroid administration and was evaluated daily during the treatment. Frequencies and latencies of mounts, intromissions, and ejaculations, as well as the postejaculatory refractory period were recorded. One hundred percent of the REMd subjects presented mounts, intromissions, and ejaculations sooner than the control group. In almost all parameters, a clear facilitation of sexual activity was observed in the REMd group.     

Sleep deprivation in Air National Guard medical personnel responding to simulated disaster-training exercises

National Guard personnel remain largely unstudied within the sleep research community, despite their unique and important role. In response, the purpose of this study was to investigate the extent of sleep deprivation in National Guard medical personnel from two separate Air Force Bases (AFBs) responding to simulated disaster-training exercises. National Guard medical personnel (N = 77) were fitted with wrist activity monitors (actigraphy) to objectively measure their sleep for 4 days of their civilian time (baseline), followed by a 4-day transition period from civilian to military duty, and a 3–5-day disaster-training exercise. Differences in sleep quantity, quality, and “cognitive effectiveness” were analyzed using generalized linear mixed models. Participants’ sleep quantity was significantly reduced from civilian to disaster-training periods, and their cognitive effectiveness also dropped significantly. National Guard medical personnel were sleep-deprived during a simulated disaster-training exercise, which, although a valid proxy for real-world disasters, is likely to be a conservative approximation of the stress and fatigue National Guard personnel experience during crisis response. As such, the need for targeted fatigue-related interventions to safeguard our service members during these critical times is clear.     

Spatial and reversal learning in the Morris water maze are largely resistant to six hours of REM sleep deprivation following training

This first test of the role of REM (rapid eye movement) sleep in reversal spatial learning is also the first attempt to replicate a much cited pair of papers reporting that REM sleep deprivation impairs the consolidation of initial spatial learning in the Morris water maze. We hypothesized that REM sleep deprivation following training would impair both hippocampus-dependent spatial learning and learning a new target location within a familiar environment: reversal learning. A 6-d protocol was divided into the initial spatial learning phase (3.5 d) immediately followed by the reversal phase (2.5 d). During the 6 h following four or 12 training trials/day of initial or reversal learning phases, REM sleep was eliminated and non-REM sleep left intact using the multiple inverted flowerpot method. Contrary to our hypotheses, REM sleep deprivation during four or 12 trials/day of initial spatial or reversal learning did not affect training performance. However, some probe trial measures indicated REM sleep-deprivation-associated impairment in initial spatial learning with four trials/day and enhancement of subsequent reversal learning. In naive animals, REM sleep deprivation during normal initial spatial learning was followed by a lack of preference for the subsequent reversal platform location during the probe. Our findings contradict reports that REM sleep is essential for spatial learning in the Morris water maze and newly reveal that short periods of REM sleep deprivation do not impair concurrent reversal learning. Effects on subsequent reversal learning are consistent with the idea that REM sleep serves the consolidation of incompletely learned items.     

Recovery of performance during sleep following sleep deprivation in older normal and insomniac adult males

Groups of 12 normal and insomniac male subjects aged 55 to 71 yr. were sleep deprived for 64 hr. In both groups, the sleep loss was preceded by four baseline sleep nights and followed by four recovery nights. Reaction time, immediate recall, sleepiness, and body temperature were measured at approximately 2300, 0115, 0330, 0530, and 0800 during baseline, deprivation and recovery nights. Significant performance or mood differences were not found between the normal and insomniac males on any measure or at any testing period throughout the study. Performance of both groups declined characteristically during sleep loss while subjective sleepiness increased. As in young adults, degraded performance was restored by 8 hr. of recovery sleep. However, subjective sleepiness did not return to baseline levels until early in the second recovery night. It was concluded that chronic insomnia does not result in group performance deficits similar to those seen after chronic sleep loss; and the restorative function of sleep operates as efficiently in older insomniac subjects (who apparently have reduced need to sleep) as in older normal subjects.     

Sleep deprivation in adolescents and adults: changes in affect

The present study investigated the impact of sleep deprivation on several aspects of affective functioning in healthy participants selected from three different developmental periods: early adolescence (ages 10-13), midadolescence (ages 13-16), and adulthood (ages 30-60). Participants completed an affective functioning battery under conditions of sleep deprivation (a maximum of 6.5 hours total sleep time on the first night followed by a maximum of 2 hours total sleep time on the second night) and rest (approximately 7-8 hours total sleep time each night for two consecutive nights). Less positive affect was observed in the sleep-deprived, compared to rested, condition. This effect held for 9 of the 12 positive affect items on the PANAS-C. Participants also reported a greater increase in anxiety during a catastrophizing task and rated the likelihood of potential catastrophes as higher when sleep deprived, relative to when rested. Early adolescents appraised their main worry as more threatening when sleep deprived, relative to when rested. These results support and extend previous research underscoring the adverse affective consequences of sleep deprivation.     

The prefrontal cortex in sleep

Experimental data indicate a role for the prefrontal cortex in mediating normal sleep physiology, dreaming and sleep-deprivation phenomena. During nonrandom-eye-movement (NREM) sleep, frontal cortical activity is characterized by the highest voltage and the slowest brain waves compared to other cortical regions. The differences between the self-awareness experienced in waking and its diminution in dreaming can be explained by deactivation of the dorsolateral prefrontal cortex during REM sleep. Here, we propose that this deactivation results from a direct inhibition of the dorsolateral prefrontal cortical neurons by acetylcholine, the release of which is enhanced during REM sleep. Sleep deprivation influences frontal executive functions in particular, which further emphasizes the sensitivity of the prefrontal cortex to sleep.     

Infant sleep-wake behaviors at two weeks,three and six months

Although infant sleep-wake behavior presents several developmental changes during the first six months, literature lacks on reference values and few studies have explored the role of individual change and stability on infant sleep-wake behavior during the first six months. This study aimed (1) to describe infant sleep-wake behaviors during the 24-h period, day and night, at two weeks, three, and six months, (2) and to explore developmental changes and the role of individual change and stability on infant sleep-wake behaviors from two weeks to six months. Ninety-four primiparous mothers completed measures on infant sleep-wake behaviors at two weeks, three and six months. Significant developmental changes were found on infant sleep-wake behaviors from two weeks to six months. Two-week-old infants sleep 13.3 h, spend 8.7 h awake, awake 6.1 times, have 0.4 h of latency to sleep, and 3.2 h of longest sleep period. Three-month-old infants sleep 13.0 h, spend 9.2 h awake, awake 5.5 times, have 0.4 h of latency to sleep, and 5.2 h of longest sleep period. Six-month-old infants sleep 12.2 h, spend 10.0 h awake, awake 5.2 times, have 0.4 h of latency to sleep, and 5.6 h of longest sleep period. Significant individual change and stability were also found on infant sleep-wake behaviors from two weeks to six months. Despite significant developmental and individual changes, individual stability explains a significant amount of the variance on infant sleep-wake behaviors over the first six months of life.     

Sleep deprivation adversely affects interpersonal responses to frustration

Sleep deprivation produces negative effects on mood and cognitive function, but existing data have almost exclusively utilized objective rating scales, which do not permit evaluation of idiosyncratic and unstructured responses. In this study, we used a semi-projective measure, the Rosenzweig Picture-Frustration (P-F) Study, to assess subjective responses to frustration following two nights without sleep. Twenty-six healthy volunteers completed the P-F at rested baseline and again following 55 h of continuous wakefulness. Participants provided written responses for an ambiguous cartoon character confronted with various frustrating situations. Relative to rested baseline, sleep deprivation was associated with altered responses on several indices, indicating a great number of uncommon types of responses, increased tendency to blame others for problems, and a reduced willingness to alleviate a conflict situation by accepting blame. Individual differences in several aspects of emotional intelligence were predictive of the extent to which responses to frustration changed with sleep loss. These findings suggest that sleep deprivation significantly weakens the inhibition of aggression and willingness to behave in ways that facilitate effective social interaction, possibly through reduced metabolic activity in prefrontal regions of the brain important for personality, affect, and inhibitory behavior.     

Paradoxical Sleep Deprivation and Sleep Recording Following Training in a Brightness Discrimination Avoidance Task in Sprague–Dawley Rats: Paradoxical Effects

Previously, we reported that posttraining paradoxical sleep deprivation (PSD) resulted in an enhancement of the subsequent avoidance performance for rats trained for 15 trials in a Y-maze brightness avoidance discrimination task. A series of experiments were conducted to try to further understand the reasons for results which were contrary to those of the bulk of the sleep-learning literature. Experiment 1 investigated the effectiveness of the PSD technique. Rats (N= 4) were sleep recorded while residing on a “swimming pool” apparatus for 24 h. Compared to their baseline values, all animals showed a very large reduction in paradoxical sleep and spent significantly more time awake. Slow-wave sleep was unchanged. In Experiment 2, proactive motor effects were tested. Rats were deprived of PS for 24 h and then tested in a hole board motor activity task. There was a slight effect of PS deprivation on the day following the PSD and no effect when the rats were retested 1 week later. Experiment 3 investigated possible proactive effects of PSD on avoidance performance. Rats exposed to PSD in the 24 h before training in the Y-maze task did not demonstrate any facilitative effect on the subsequent avoidance performance. Experiment 4 investigated the possibility that the PSD facilitative effect could be due to partial training. Rats were given 75 acquisition trials in the brightness discrimination Y-maze avoidance before being subjected to 24 h of PSD. PS-deprived animals showed superior avoidance scores compared to non-PSD controls when retested 24 h later. In Experiment 5, the same strain of rats (N= 11) were sleep recorded after exposure to a partial acquisition in a Y-maze brightness avoidance discrimination task. They were then continuously monitored for 4 consecutive days. The percent PS for the Trained rats was significantly lower than that for the Control animals. This drop in percent PS was not confined to any particular time period in the 24-h day. None of the other sleep parameters reached significance. Analyses of the present results suggest that PSD exerts its facilitative effects on posttraining consolidation processes. We present arguments suggesting that PSD can have effects opposite to those generally reported, in animals demonstrating poor avoidance abilities, in an avoidance task.     

Sleep deprivation adversely affects interpersonal responses to frustration

Sleep deprivation produces negative effects on mood and cognitive function, but existing data have almost exclusively utilized objective rating scales, which do not permit evaluation of idiosyncratic and unstructured responses. In this study, we used a semi-projective measure, the Rosenzweig Picture-Frustration (P-F) Study, to assess subjective responses to frustration following two nights without sleep. Twenty-six healthy volunteers completed the P-F at rested baseline and again following 55 h of continuous wakefulness. Participants provided written responses for an ambiguous cartoon character confronted with various frustrating situations. Relative to rested baseline, sleep deprivation was associated with altered responses on several indices, indicating a great number of uncommon types of responses, increased tendency to blame others for problems, and a reduced willingness to alleviate a conflict situation by accepting blame. Individual differences in several aspects of emotional intelligence were predictive of the extent to which responses to frustration changed with sleep loss. These findings suggest that sleep deprivation significantly weakens the inhibition of aggression and willingness to behave in ways that facilitate effective social interaction, possibly through reduced metabolic activity in prefrontal regions of the brain important for personality, affect, and inhibitory behavior.     

Effects of sleep deprivation on Color-Word, Emotional, and Specific Stroop interference and on self-reported anxiety

The aim of this study was principally to assess the impact of sleep deprivation on interference performance in short Stroop tasks (Color-Word, Emotional, and Specific) and on subjective anxiety. Subjective sleepiness and performance on a psychomotor sustained attention task were also investigated to validate our protocol of sleep deprivation. Twelve healthy young subjects were tested at four-hourly intervals through a 36-h period of wakefulness under a constant routine protocol. Analyses of variance for repeated measurements revealed that self-assessment of sleepiness on a visual analogue scale as well as mean reaction time performance on the sustained attention task, both for the first minute and for 10 min of testing, were worsened by sleep deprivation. Analyses revealed an increase in self-reported anxiety scores on the STAI questionnaire but did not reveal any significant effect after sleep deprivation either on indexes of interference or on accuracy in Stroop tasks. However, analyses showed sensitivity to circadian effect on verbal reaction times in the threat-related (Emotional) and sleep-related (Specific) Stroop tasks. We concluded that 36 h of prolonged wakefulness affect self-reported anxiety and Emotional Stroop task resulting in a cognitive slowing. Moreover, total sleep deprivation does not affect interference control in any of the three short Stroop tasks.