The effects of task duration and work-session location on performance degradation induced by sleep loss and sustained cognitive work

Studies attempting to estimate the degree of performance degradation resulting from sleep loss typically use relatively long-duration tasks that are distinctly separate from ongoing activities. Since long-duration tasks are not practical for assessing the performance degradation induced by sleep loss in field settings, this study was designed to examine whether the results of short-duration (1-min) tasks were markedly different from those of long-duration (10-min) tasks with respect to detecting performance changes during a 54-h period of sleep loss and sustained cognitive work. Performance changes also were examined as a function of the location of tasks within work sessions by comparing performance on 1-min tasks that were placed within work sessions with those tasks that immediately followed short rest periods. The results showed that short-and long-duration tasks were equally sensitive to sleep loss. In addition, once sleep-deprivation effects began to emerge, it was found that performance on short-duration tasks within work sessions showed significantly more impairment than performance on tasks that followed rest breaks. These results suggest that task duration is not a critical factor for detecting performance degradation induced during continuous work experiments but that the location of tasks within work sessions is critical for accurately assessing expected performance.     

Sleep quality, sleep propensity and academic performance

We examined associations between measures of sleep propensity on the Epworth Sleepiness Scale, sleep quality on the Pittsburgh Sleep Quality Index and academic performance by GPA and grades in introductory psychology for 414 students. In the total sample, neither sleep propensity nor sleep quality correlated with GPA or introductory psychology grades. However, among students carrying a full course load, those reporting poor sleep quality performed less well on academic measures than those reporting a better quality of sleep. Further research is needed to assess the moderating influence of overall demands of daytime functioning on the association between sleep quality and academic performance.     

Effects of a limited nap on night sleep in older subjects

The night sleep of sixteen 50-60-year-old women, which had been preceded by either afternoon naps or no-nap control periods, was assessed by polygraphic and subjective measures. There were 2 nap and 2 non-nap nights. The naps were limited to a 1-hr opportunity. The measures of all subjects, good nappers (more than 20-min sleep on both nap occasions), and subjects with 50-min or more nap time, were separately analyzed. The null hypothesis of a nap effect could not be rejected. Within limits, naps may be recommended to offset the common night-time awakenings in older persons.     

Circadian rhythms determined by cosine curve fitting: Analysis of continuous work and sleep-loss data

In this study, we report the effects of sleep loss upon circadian rhythm parameters analyzed by the cosine curve fitting (cosinor) method. Rhythm alterations are described as reductions in rhythm strength, increases in individual variations producing an increase in the 95% confidence limits, and reductions in rhythm amplitude. Subjects worked continuously at tasks for 45 h with time-of-day cues. Circadian cycles in physiological and mood variables remained intact, but rhythms in some task performance measures no longer showed significant 24-h/cycle activities. The relationship between oral temperature, mood, and pulse rhythms continued undisturbed during the continuous work period; however, the performance linkage to oral temperature was lost. These findings direct attention to individual difference in susceptibility to continuous work periods and suggest that 24-h rhythms in some performance and physiological measures perhaps are more readily responsive to an altered wake/sleep cycle than other circadian rhythms.     

Sleep fragmentation and lucid dreaming

Lucid dreaming—the phenomenon of experiencing waking levels of self-reflection within one’s dreams—is associated with more wake-like levels of neural activation in prefrontal brain regions. In addition, alternating periods of wakefulness and sleep might increase the likelihood of experiencing a lucid dream. Here we investigate the association between sleep fragmentation and lucid dreaming, with a multi-centre study encompassing four different investigations into subjective and objective measures of sleep fragmentation, nocturnal awakenings, sleep quality and polyphasic sleep schedules. Results across these four studies provide a more nuanced picture into the purported connection between sleep fragmentation and lucid dreaming: While self-assessed numbers of awakenings, polyphasic sleep and physiologically validated wake-REM sleep transitions were associated with lucid dreaming, neither self-assessed sleep quality, nor physiologically validated numbers of awakenings were. We discuss these results, and their underlying neural mechanisms, within the general question of whether sleep fragmentation and lucid dreaming share a causal link.     

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.     

Methamphetamine effects on cognitive processing during extended wakefulness

We examined the effects of both 5- and 10-mg/7O kg body weight of d-methamphetamine HCl on high event rate vigilance and tracking performance in a 13.5-hr sustained-performance session during one night of sleep loss. At 0116 hours participants were administered either a 5 mg/70 kg oral dose of d-methamphetamine (n=10), 10 mg/70 kg d-methamphetamine (n=10), or a placebo (n=10) using standard double-blind procedures. Performance on all measures degraded markedly during the night in the placebo group. Both the 5- and 10-mg methamphetamines treatment reversed an initial decline in d', and reversed increases in nonresponses (lapses) and tracking error within approximately 3 hr of administration. No evidence that amphetamine treatment increased impulsive responding (fast guesses) was observed. The magnitude of the performance effects of the methamphetamine treatments was similar at 3 hr postadministration. However, the effects of the 5-mg dose were shorter-lived, disappearing by the last testing session (6.5 hr postadministration), whereas effects of the 10-mg dose tended to remain throughout testing. Both amphetamine treatments decreased subjective sleepiness during the night and tended to increase subjective sleep latencies during a post-testing sleep period.     

Exploring the within-person coupling of sleep and cognition in older African Americans

This study examined the within-person relationship between sleep and cognitive functioning. Fifty community-dwelling African Americans (age range = 50-80 years) were asked to report their sleep duration and quality the previous evening and to complete cognitive measures over 8 occasions within a 2-3 week period. A within-person daily change in sleep duration was significantly associated with worse global cognitive performance. The greater an individual deviated away from his or her average sleep duration on a particular day, the more likely his or her performance would decline. These results demonstrate that the sleep-cognition relationship can be observed at a within-person level of analysis.     

Sleep interventions for performance,mood and sleep outcomes in athletes: A systematic review and meta-analysis

Sleep is fundamental to sports performance and other health outcomes such as mental wellbeing. This systematic review explored the effects of sleep interventions implemented among athletes on performance, sleep, and mood outcomes. Five databases were searched, returning 5996 records for screening. Of these, 27 articles met the inclusion criteria (16 controlled deigns, 11 uncontrolled; athletes n = 617; male n = 432, female n = 93, non-binary/other n = 0 or not reported n = 92). Narrative synthesis of all studies based on intervention type suggested that sleep hygiene, assisted sleep, and sleep extension interventions may be associated with improved sleep, performance, and mood outcomes. Twelve controlled trials were eligible for quantitative meta-analysis, investigating the effect of sleep interventions on athlete sleep, performance, and negative affect, compared to controls post-intervention. Utilizing random-effects meta-analyses, sleep interventions improved subjective sleep quality (g = 0.62, 95% CI [0.21, 1.02]), reduced sleepiness (g = 0.81, 95% CI [0.32, 1.30]) and decreased negative affect (g = 0.63, 95% CI [0.27, 0.98]), but did not appear to influence subjective sleep duration. No effects were identified for objective sleep measures (e.g., actigraphy), or aerobic/anaerobic performance indices. While sleep interventions may offer some benefit to athletes, caution is warranted given limitations of the extant research relating to small, non-representative studies with methodological concerns.     

Use of Stimulants to Ameliorate the Effects of Sleep Loss During Sustained Performance

A variety of experimental approaches is presently under investigation to study the impact of stimulant drugs on anticipated decrements of performance due to sleep loss and sustained operations. The drugs have been used either in a preventive (maintenance) paradigm designed to maintain behavior over long periods of time or in a recovery paradigm designed to offset the effects of sleep deprivation and/or sustained performance. Several such studies are reviewed and their results evaluated. Questions concerning theoretical and practical applications are raised, and suggestions for future research are discussed.     

Effects of acute sleep restriction on behavior, sustained attention, and response inhibition in children.

This study examined the effects of acute sleep restriction on the day-time behavior and performance of healthy children and adolescents. 82 participants (8 to 15 years of age) completed 5 nights of baseline sleep and were randomly assigned to Optimized (10 hr.) or Restricted (4 hr.) sleep for an overnight lab visit. Behavior, performance, and sleepiness were assessed the following day. Sleep restriction was associated with shorter daytime sleep latency, increased subjective sleepiness, and increased sleepy and inattentive behaviors but was not associated with increased hyperactive-impulsive behavior or impaired performance on tests of response inhibition and sustained attention. Results are discussed in terms of current theories regarding effects of inadequate or disturbed sleep among children and adolescents.     

A Study of Seventh Grade Children's Reading of Comic Books as Related to Certain other Variables

Developmental changes in a variety of cognitive processes as a function of age and schooling were examined in 160 rural Guatemalan children aged 5, 7, 9, and 11 years. Larger differences in test performance were seen between ages 9 and 11 than during earlier age periods on most tasks. Regression analyses of years of schooling controlling for age, sex, and socioeconomic status indicated that the effects of school were limited to memory tasks and to response time on the Matching Familiar Figures Test (MFF). Evidence for cumulative effects of additional years in school on test performance was weak. Good school performance was also most related to two memory measures. Previous studies indicating that schooling has a substantial effect on abstract cognitive processes were questioned; the suggestion that school performance is related to various memory processes was raised.     

Electroencephalographic and autonomic alterations in subjects with frequent nightmares during pre-and post-REM periods

Abnormal arousal processes, sympathetic influences, as well as wake-like alpha activity during sleep were reported as pathophysiological features of Nightmare Disorder. We hypothesized that in Nightmare Disorder, wake-like cortical activity and peripheral measures linked to arousals would be triggered by physiological processes related to the initiation of REM periods. Therefore, we examined electroencephalographic (EEG), motor and autonomous (cardiac) activity in a group of nightmare (NM) and healthy control (CTL) subjects during sleep-state-transitions while controlling for the confounding effects of trait anxiety. Based on the second-nights’ polysomnographic recordings of 19 Nightmare Disordered (NM) and 21 control (CTL) subjects, we examined the absolute power spectra focusing on the alpha range, measures of heart rate variability (HRV) and motor (muscle tone) activity during pre-REM and post-REM periods, separately. According to our results, the NM group exhibited increased alpha power during pre-REM, but not in post-REM, or stable, non-transitory periods. While CTL subjects showed increased HRV during pre-REM periods in contrast to post-REM ones, NM subjects did not exhibit such sleep state-specific differences in HRV, but showed more stable values across the examined sleep stages and less overall variability reflecting generally attenuated parasympathetic activity during sleep-state-transitions and during stable, non-transitory NREM states. These differences were not mediated by waking levels of trait anxiety. Moreover, in both groups, significant differences emerged regarding cortical and motor (muscle tone) activity between pre-REM and post-REM conditions, reflecting the heterogeneity of NREM sleep. Our findings indicate that NM subjects’ sleep is compromised during NREM–REM transitions, but relatively stabilized after REM periods. The coexistence of sleep-like and wake-like cortical activity in NM subjects seems to be triggered by REM/WAKE promoting neural activity. We propose that increased arousal-related phenomena in NREM–REM transitions might reflect altered emotional processing in NM subjects.     

Three consecutive nights of sleep loss: Effects of morning caffeine consumption on subjective sleepiness/alertness,reaction time and simulated driving performance

Caffeinated products are often consumed as a popular countermeasure to the effects of sleep loss. However, the efficacy of caffeine to exert these effects after consecutive nights of sleep loss is poorly understood. The aim of this study was to investigate the effects of three consecutive nights of restricted sleep and morning caffeine consumption on subjective ratings of sleepiness/alertness, reaction time, and simulated driving performance. Twenty healthy, habitual caffeine consumers (11 females; age: 23.3 ± 5.7 y; BMI: 22.3 ± 3.5 kg⋅m⁻²; caffeine intake: 204 ± 89 mg⋅day⁻¹; Mean ± SD) who had normal sleeping patterns (≥8 h⋅night⁻¹) participated in this double-blind, placebo-controlled, randomised study. Following one night of normal sleep (≥8 h time in bed (TIB)), participants underwent three consecutive nights of restricted sleep (5 h TIB). Participants received caffeine (200 mg; n = 10) or placebo (n = 10) capsules each morning and all participants received caffeine (100 mg) capsules each afternoon. Subjective ratings of alertness, concentration and tiredness were measured before and 1 h after morning capsule administration. Choice Reaction Time (CRT) was examined 1 h after morning capsule administration, with response speed and accuracy as outcome variables. Driving performance was assessed using a 30 min simulated driving task, with lateral (standard deviation of lane position [SDLP]; total number of line crossings [LC]) and longitudinal (standard deviation of speed [SDSP]) measures of vehicle control as outcome variables. Alertness and concentration significantly decreased, and tiredness increased across the three days of sleep loss. Caffeine only marginally alleviated these effects. No differences were observed between treatments or across trial days for response speed and accuracy on the CRT task. Likewise, no significant differences were observed between groups or across trial days for any measures of simulated driving performance. Overall, results from this study indicate that three consecutive days of sleep loss influence subjective ratings of alertness, concentration and tiredness, but does not alter CRT or simulated driving performance. Caffeine may alleviate some of the negative subjective effects imposed by restricted sleep, but the efficacy of caffeine to attenuate performance changes in CRT and driving performance were unable to be observed.     

A daytime nap containing solely non-REM sleep enhances declarative but not procedural memory

The specialized role that sleep-specific brain physiology plays in memory processing is being rapidly clarified with a greater understanding of the dynamic, complex, and exquisitely orchestrated brain state that emerges during sleep. Behaviorally, the facilitative role of non-REM (NREM) sleep (primarily slow wave sleep) for declarative but not procedural memory performance in humans has been demonstrated in a number of nocturnal sleep studies. However, subjects in these studies were tested after periods of sleep that contained REM sleep in addition to NREM sleep, and comparison wake groups were subjected to mild sleep deprivation. To add some clarity to the findings of these nocturnal studies, we assessed performance on declarative and procedural memory tasks following a daytime training-retest interval containing either a short nap that included NREM without REM sleep, or wakefulness. Consistent with previous findings we show that, after a comparatively brief sleep episode, subjects that take a nap improve more on a declarative memory task than subjects that stay awake, but that improvement on a procedural memory task is the same regardless of whether subjects take a nap or remain awake. Slow wave sleep was the only sleep parameter to correlate positively with declarative memory improvement. These findings are discussed with reference to the general benefits of napping and within the broader context of a growing literature suggesting a role for NREM-specific physiology for the processing of declarative memory.     

Awareness during drowsiness: dynamics and electrophysiological correlates.

During drowsy periods, performance on tasks requiring continuous attention becomes intermittent. Previously, we have reported that during drowsy periods of intermittent performance, 7 of 10 participants performing an auditory detection task exhibited episodes of non-responding lasting about 18 s (Makeig & Jung, 1996). Further, the time patterns of these episodes were repeated precisely in subsequent sessions. The 18-s cycles were accompanied by counterbalanced power changes within two frequency bands in the vertex EEG (near 4 Hz and circa 40 Hz). In the present experiment, performance patterns and concurrent EEG spectra were examined in four participants performing a continuous visuomotor compensatory tracking task in 15-20 minute bouts during a 42-hour sleep deprivation study. During periods of good performance, participants made compensatory trackball movements about twice per second, attempting to keep a target disk near a central ring. Autocorrelations of time series representing the distance of the target disk from the ring centre showed that during periods of poor performance marked near-18-s cycles in performance again appeared. There were phases of poor or absent performance accompanied by an increase in EEG power that was largest at 3-4 Hz. These studies show that in drowsy humans, opening and closing of the gates of behavioural awareness is marked not by the appearance of (12-14 Hz) sleep spindles, but by prominent EEG amplitude changes in the low theta band. Further, both EEG and behavioural changes during drowsiness often exhibit stereotyped 18-s cycles.     

Effects of sleep deprivation on short-term recognition memory.

A probe-recognition short-term memory paradigm was used to inquire into the precise effects of sleep deprivation on human memory. It was found that recognition performance, as measured by d', was generally impaired for each subjects after 24 hr of sleep deprivation. While d' was shown to decrease exponentially as the number of items intervening between the target and the probe increased, this decay rate was not affected by sleep loss. In addition there was confirmation of a previously observed increase in the positive skewness of reaction times after wakefulness. The data were consistent with the hypothesis that sleep deprivation increases the occurrence of lapses, periods of lowered reactive capacity, which prevent the encoding of items in short-term memory.     

Effects of acute simulated microgravity on nocturnal sleep, daytime vigilance, and psychomotor performance: comparison of horizontal and 6 degrees head-down bed rest

This study examined the effect of acute simulated microgravity on nocturnal sleep, daytime vigilance, and psychomotor performance. Each of 7 volunteers were maintained for 3 days of head-down and horizontal bed rest in a counter-balanced design. Assessment measures were polysomnographic recordings on the first night and performance on psychophysiological tasks on the second day involving subjective and objective vigilance, P300, simple reaction time tasks, and dual performance tasks. No clear difference in sleep structure was observed between the head-down and horizontal conditions, except for a slight decrease in Stage 4 for head-down. Both subjective and objective daytime vigilance, P300, and the simple RT task showed no statistical difference, although tracking performance on the dual task showed deterioration at 10:00 for the head-down condition. These results suggest that nocturnal sleep, daytime vigilance, and psychophysiological functions were not disturbed in head-down sleep conditions, although there was a mild deterioration of higher attentional function in the morning.     

Sleep-competing behaviours among Australian school-attending youth: Associations with sleep,mental health and daytime functioning

Sleep problems are highly prevalent among school-attending youth, and impact on school performance and outcomes. Sleep-competing behaviours are likely factors in the inadequate sleep time and related functional outcomes observed in this population. We examined a range of sleep-competing behaviours and their associations with sleep variables in Australian school-attending youth. We also assessed whether these behaviours indirectly affected mental health and daytime functioning through poorer sleep quality. A total of 353 school-attending youth (mean age = 14.6 years, 53% female) were recruited from high schools in Australia, and completed a range of self-report measures. Approximately 50% of the youth obtained sub-optimal levels of sleep and reported having a problematically long sleep onset latency. Sleep competing behaviours, related and unrelated to electronic media use, were reported as occurring frequently, and were associated with a range of sleep variables. These behaviours were also related to poorer mental health and daytime sleepiness, with this association explained by indirect effects through sleep quality. Sleep-competing behaviours are prevalent on school nights in Australian youth, and may have adverse associations with mental health and functioning. Prevention and intervention programs might address the risk factors identified in the current study.     

Use of the Sleep Assessment Device (Kelley and Lichstein, 1980) to validate insomniacs' self-report of sleep pattern

A comparison is presented of insomniacs' self-reported sleep pattern and objectively monitored sleep using the Sleep Assessment Device (SAD; Kelley & Lichstein, 1980). Analysis of 110 subject nights revealed modest but significant subjective overestimates of both sleep latency and sleep duration which were accounted for by the demands of the task (i.e., longer time periods are harder to estimate accurately). Correlations between self-report and SAD measures were, however, consistently high, suggesting that self-report may be a valid index of sleep disturbance. Results are discussed with reference to the clinician's task in evaluating sleep complaints.This research stury was supported by a grant from the Research Fund of Lanarkshire Health Board, Scotland.