Continuous Sleep Deprivation Research Articles

Effects of total sleep deprivation on functional connectivity of the anterior cingulate cortex: Insights from resting-state fMRI in healthy adult males

Inadequate sleep significantly impacts an individual's health by compromising inhibitory control and self-regulation abilities. This study employed resting-state functional magnetic resonance imaging (fMRI) to assess the functional connectivity between the anterior cingulate cortex (ACC) and the whole brain in 16 healthy adult males after 36 h of total sleep deprivation. Additionally, this study investigated alterations in individuals' inhibitory control functions and physiological mechanisms following sleep deprivation. The results showed a significant increase in functional connectivity between the ACC, the left angular gyrus, and the right hippocampus following 36 h of continuous sleep deprivation. Conversely, functional connectivity was notably decreased between the ACC and the right insular cortex, right paracingulate gyrus, and bilateral putamen. Furthermore, changes in ACC functional connectivity were significantly correlated with alterations in behavioral performance in the go/no-go task after sleep deprivation. This study contributes to understanding brain network mechanisms in the anterior cingulate gyrus after sleep deprivation. It clarifies the relationship between functional connectivity changes in the anterior cingulate gyrus and inhibitory control post-sleep deprivation.

Understanding the impact of sociosexual interactions on sleep using Drosophila melanogaster as a model organism.

Sleep is conserved across species, and it is believed that a fixed amount of sleep is needed for normal neurobiological functions. Sleep rebound follows sleep deprivation; however, continuous sleep deprivation for longer durations is believed to be detrimental to the animal's wellbeing. Under some physiologically demanding situations, such as migration in birds, the birth of new offspring in cetaceans, and sexual interactions in pectoral sandpipers, animals are known to forgo sleep. The mechanisms by which animals forgo sleep without having any obvious negative impact on the proper functioning of their neurobiological processes are yet unknown. Therefore, a simple assay is needed to study how animals forgo sleep. The assay should be ecologically relevant so it can offer insights into the physiology of the organisms. Equally important is that the organism should be genetically amenable, which helps in understanding the cellular and molecular processes that govern such behaviors. This paper presents a simple method of sociosexual interaction to understand the process by which animals forgo sleep. In the case of Drosophila melanogaster, when males and females are in proximity, they are highly active and lose a significant amount of sleep. In addition, there is no sleep rebound afterward, and instead, males engaged in sexual interactions continue to show normal sleep. Thus, sexual drive in the fruit flies is a robust assay to understand the underlying mechanism by which animals forgo sleep.

Altered cognition and anxiety in adolescent offspring whose mothers underwent different-pattern maternal sleep deprivation, and cognition link to hippocampal expressions of Bdnf and Syt-1.

Inadequate sleep during pregnancy negatively affects the neural development of offspring. Previous studies have focused on the continuous sleep deprivation (CSD) paradigm, but the sleep pattern during late pregnancy is usually fragmented. To compare the effects of CSD and fragmented sleep deprivation (FSD) in late pregnancy on emotion, cognition, and expression of synaptic plasticity-related proteins in offspring mice. Pregnant CD-1 mice were either subjected to 3/6 h of CSD/FSD during gestation days 15-21, while those in the control group were left untreated. After delivery, the offspring were divided into five groups, i.e., control (CON), short or long CSD (CSD3h, CSD6h), and short or long FSD (FSD3h, FSD6h). When the offspring were 2 months old, the anxiety-like behavior level was tested using the open field (OF) and elevated plus maze (EPM) test, and spatial learning and memory were evaluated using the Morris water maze (MWM) test. The expression of hippocampal of brain-derived neurotrophic factor (Bdnf) and synaptotagmin-1 (Syt-1) was determined using RT-PCR and western blotting. The CSD6h, FSD3h, and FSD6h had longer latency, fewer center times in the OF test, less open arms time and fewer numbers of entries in the open arms of the EPM, longer learning distance swam and lower memory percentage of distance swam in the target quadrant in the MWM test, and decreased BDNF and increased Syt-1 mRNA and protein levels in the hippocampus. Compared to the CSD6h, the FSD3h and FSD6h had longer distance swam, a lower percentage of distance swam in the target quadrant, decreased BDNF, and increased Syt-1 mRNA and protein levels in the hippocampus. The results suggested that maternal sleep deprivation during late pregnancy impairs emotion and cognition in offspring, and FSD worsened the cognitive performance to a higher extent than CSD. The observed cognitive impairment could be associated with the expression of altered hippocampal of Bdnf and Syt-1 genes.

Sleep loss suicidal ideation: the role of trait extraversion

Background: It is known that sleep disturbance is associated with increased suicidal thinking. Moreover, completed suicides, when adjusted for the proportion of the populace that is awake at a given time, are more probable during the late night/early morning hours. Despite these concerns, no studies have examined the role of trait-like individual differences in vulnerability to suicidal ideation during sleep deprivation or insomnia. In two separate studies, we examined whether the trait of extraversion is predictive of changes in suicidal thinking following two nights of sleep deprivation and among individuals meeting the criteria for insomnia. Methods: Study 1: Twenty-five healthy military personnel (20 males), ages 20-35 completed the NEO-PI-R Extraversion scale and the Suicidal Ideation (SUI) scale of the Personality Assessment Inventory (PAI). Participants completed 77 h of continuous sleep deprivation. After 56 h of sleep deprivation, participants completed the SUI scale a second time. We predicted a change in SUI scores from baseline extraversion. Study 2: 2,061 adults aged 18-79 (900 males) were divided into two groups based on the clinical threshold (≥ 10) on the Insomnia Severity Index (ISI) and completed measures of extraversion and depression, including the suicide item of the Patient Health Questionnaire-9 (PHQ9). Results: Study 1: After controlling for the caffeine group and changes in PAI Depression, Extraversion scores were used to predict changes in SUI scores using stepwise multiple linear regression. Higher Extraversion was significantly associated with increased non-clinical suicidal ideation following sleep loss, β = 0.463, partial r = 0.512, p = 0.013. Study 2: After controlling for depression, the effect of insomnia on suicidal ideation was moderated by trait extraversion (p < 0.0001). Overall, the presence or absence of insomnia had little effect on individuals low in trait extraversion (i.e., introverts), but insomnia was associated with significantly higher suicidal ideation among high trait extraverted individuals. Conclusions: Higher trait extraversion was associated with increased vulnerability to suicidal ideation between rested baseline and total sleep deprivation and was associated with greater suicidal ideation among those meeting criteria for clinically severe insomnia. These findings point to a potential trait-like vulnerability factor that may further our understanding of sleep disruption in the phenomenology of suicide.

Study on homeostasis and circadian rhythm of attention performance of different chronotypes in sleep deprivation

Difference of chronotypes makes influence to cognitive performance of individuals in routine duties. In this paper, 55 subjects with different chronotypes were subjected to continuous sleep deprivation for 30 h by using the constant routine protocol, during which core body temperature was measured continuously, and subjective sleepiness self-rating and the performance of selective attention were measured hourly. The results showed that the phase difference of core body temperature has no significant difference, yet the amplitude and term difference among the three chronotypes are significant. There was an advance in phase between subjective sleepiness self-rating and core body temperature, and the self-rating sleepiness of evening type came the latest, and the self-rating sleepiness of morning type dissipated the fastest. The response time of selective attention showed a 2 h phase delay with subjective sleepiness self-rating. And the analysis of core body temperature showed that the later the chronotype was, the greater the phase delay was. The correct rate of selective attention of different chronotypes were inconsistent with delay of subjective sleepiness self-rating and core body temperature. We provide reference for industry, aviation, military, medical and other fields to make a more scientific scheduling/ shifting based on cognitive performance characteristics of different chronotypes.

Activation of CNR1/PI3K/AKT Pathway by Tanshinone IIA Protects Hippocampal Neurons and Ameliorates Sleep Deprivation-Induced Cognitive Dysfunction in Rats

Sleep deprivation is commonplace in modern society, Short periods of continuous sleep deprivation (SD) may negatively affect brain and behavioral function and may lead to vehicle accidents and medical errors. Tanshinone IIA (Tan IIA) is an important lipid-soluble component of Salvia miltiorrhiza, which could exert neuroprotective effects. The aim of this study was to investigate the mechanism of neuroprotective effect of Tan IIA on acute sleep deprivation-induced cognitive dysfunction in rats. Tan IIA ameliorated behavioral abnormalities in sleep deprived rats, enhanced behavioral performance in WMW and NOR experiments, increased hippocampal dendritic spine density, and attenuated atrophic loss of hippocampal neurons. Tan IIA enhanced the expression of CB1, PI3K, AKT, STAT3 in rat hippocampus and down-regulated the expression ratio of Bax to Bcl-2. These effects were inhibited by cannabinoid receptor 1 antagonist (AM251). In conclusion, Tan IIA can play a neuroprotective role by activating the CNR1/PI3K/AKT signaling pathway to antagonize apoptosis in the hippocampus and improve sleep deprivation-induced spatial recognition and learning memory dysfunction in rats. Our study suggests that Tan IIA may be a candidate for the prevention of sleep deprivation-induced dysfunction in spatial recognition and learning memory.

Quality of sleep among oncology nurses and intensive care nurses: A comparative study

Background: Nurses working in shift duties, including night duties, are subject to a cumulative sleep debt, a decreased quantity and quality of sleep, and continuous sleep deprivation. Hence, nurses working in shift duties are prone to sleep disturbance. Objective: To determine and compare the quality of sleep among oncology and intensive care unit (ICU) nurses. Materials and Methods: Descriptive approach was adopted for this study. The sample comprised 126 nurses working at the units of Prince Bijay Singh Memorial (PBM) Hospital, Bikaner, Rajasthan, who were selected by purposive sampling technique. The quality of sleep was assessed by the Pittsburgh Sleep Quality Index (PSQI). Data were analyzed by using the Statistical Package for the Social Sciences (SPSS) software program, version 20.0. Results: In this study, majority of the participants (60.32%) were men. Majority of the nurses (75.40%) were working on a regular basis. The mean sleep quality scores of intensive care and oncology nurses were 3.863 ± 1.988 and 5.317 ± 1.899, respectively. The observed difference was statistically significant (t = 4.097; p < 0.001). Overall, there was poor quality of sleep in 46% of the participants. The intensive care unit (ICU) nurses are more likely to have poor quality of sleep than oncology nurses (61.90% vs. 30.16%; Χ2 = 18.15; p < 0.001). In addition, a moderate positive correlation (r = 0.6645, P = 0.0001*) was observed between the sleep quality of ICU and oncology nurses. Among the intensive care nurses and oncology nurses, there was no significant association between sociodemographic variables such as gender, age, working status, job status, and the PSQI scores. (P > 0.05). Conclusion: Intensive care nurses and oncology nurses have poor quality of sleep, which can affect their health and professional performance. The ICU nurses have poorer quality of sleep than oncology nurses. Nurse administrators and hospital administration should take initiatives to reduce the prevalence of poor sleep among these nurses.

786 Trait Extraversion is Associated with Increased Suicidal Ideation During Total Sleep Deprivation and Insomnia

Abstract Introduction It is known that sleep disturbance is associated with increased suicidal thinking, and completed suicides are most common during the late night/early morning hours, but no studies have examined the role of trait-like individual differences in vulnerability to suicidal ideation during sleep deprivation or insomnia. In two separate studies, we examined whether the trait of extraversion is predictive of changes in suicidal thinking following two nights of sleep deprivation and among individuals meeting criteria for insomnia. Methods Study 1: Twenty-five healthy military personnel (20 males), ages 20–35 completed the NEO-PI-R Extraversion scale and the Suicidal Ideation (SUI) scale of the Personality Assessment Inventory (PAI). Participants completed 77 hours of continuous sleep deprivation. After 56 hours of sleep deprivation, participants completed the SUI scale a second time. Study 2: 1,011 adults aged 18–79 (470 males) were divided into two groups based on the clinical threshold (≥15) on the Insomnia Severity Index (ISI) and completed measures of extraversion and depression, including the suicide item of the Patient Health Questionnaire-9 (PHQ9). Results Study 1: After controlling for caffeine group and changes in PAI Depression, Extraversion scores were used to predict changes in SUI scores using stepwise multiple linear regression. Higher Extraversion was significantly associated with increased non-clinical suicidal ideation following sleep loss, β=.463, partial r=.512, p=.013. Study 2: After controlling for depression, extraversion was more strongly correlated with greater suicidal ideation, particularly for those meeting criteria for insomnia, β=.340, partial r=.387, p&amp;lt;.0000001, compared to those below the threshold, β=.185, partial r=.218, p&amp;lt;.0000001. Conclusion Higher trait extraversion was associated with increased vulnerability to suicidal ideation between rested baseline and total sleep deprivation, and was associated with greater suicidal ideation among those meeting criteria for clinically severe insomnia. These findings point to a potential trait-like vulnerability factor that may further our understanding of sleep disruption in the phenomenology of suicide. Support (if any):

Effect of Confucius’ Pillow Elixir on Cognitive Ability of Agrypnia Mice and Its Mechanism

Aim: To investigate the influence of Confucius’ Pillow Elixir on cognitive ability of agrypnia mice and its mechanism. Methods: Twenty-four mice were randomly divided into normal group, model group, Confucius’ Pillow Elixir group and Diazepam group. Mice were suffered from continuous sleep deprivation with improved multi-platform water environment sleep deprivation boxes. Normal group and model group were given the same amount of normal saline, Confucius’ Pillow Elixir group was given Confucius’ Pillow Elixir decoction and Diazepam group were given Diazepam. During the experiment, we need to observe and record the general state and body weight of each group of mice. The open-field experiment and Morris water maze were conducted. Gamma-aminobutyric acid (GABA) concentration in serum of mice was determined by Elisa. Results: In the open-field experiment, compared with the model group, the number of horizontal motion grids in the Confucius’ Pillow Elixir group increased significantly, with statistical difference (P<0.05).In the Morris water maze positioning navigation test, compared with the model group, the escape latency of Confucius’ Pillow Elixir group was significantly reduced, with statistical difference (P<0.01). Compared with the model group, the GABA concentration in Confucius’ Pillow Elixir group was significantly decreased, with statistical difference (P<0.01).

Effects of 72 Hours Sleep Deprivation on Liver Circadian Clock Gene Expression and Oxidative Stress in Rats

Objective: To investigate the effects of 72 hours continuous sleep deprivation (SD) on circadian clock gene expression and oxidative stress in the rat liver. Methods: Twenty healthy male Sprague-Dawley rats were divided into 2 groups (n = 10 each) using a random number table: normal control group (group C), sleep deprivation group (group SD). Group SD was treated with a modified multiple platform water environment method. After 72 hours sleep deprived, the levels of AST (Aspartate transaminase ) and ALT (Alanine aminotransferase) in serum were determined. The contents of malondialdehyde (MDA), the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in the liver tissue of the rats were examined in both two groups. The expression levels of CLOCK, BMAL1 and CRY1 protein in liver tissue were examined by Western blotting. Results: Compared with group C, the content of MDA, and the levels of AST and ALT in serum were significantly increased (P < 0.05); SOD activity was significantly decreased (P < 0.05); GSH-Px activity was significantly decreased (P < 0.01); and the expression of CLOCK, BMAL1 and CRY1 protein was downregulated in group SD. Conclusion: 72 hours continuous sleep deprivation can downregulate the expression of circadian clock gene and promote oxidative stress in rats.

Changes in physiological tremor resulting from sleep deprivation under conditions of increasing fatigue during prolonged military training.

The aim of the study was to define the changes of the characteristics of physiological postural tremor under conditions of increasing fatigue and lack of sleep during prolonged military training (survival). The subjects of the study were 15 students of the Polish Air Force Academy in Dęblin. The average age was 19.9±1.3 years. During the 36-hour-long continuous military training (survival) the subjects were deprived of sleep. Four tremor measurements were carried out for each of the subjects: Day 1 – morning, after rest (measurement 0); Day 2 – morning, after overnight physical exercise (measurement 1); afternoon, after continuous sleep deprivation (measurement 2); Day 3 – morning, after a full night sleep (measurement 3). The accelerometric method using an acceleration measuring kit was applied to analyse tremor. A significant difference between mean values of the index evaluating tremor power in low frequencies L2-4 in measurement 0 and measurement 3 was observed (p<0.01). No significant differences were found in mean values of index L10-20. Mean frequencies F2-4 differed significantly from each other (F2,42=4.53; p<0.01). Their values were 2.94±0.11, 2.99±0.9, 2.93±0.07 and 2.91±0.07 for successive measurements. A gradual, significant decrease of F8-14 was observed (F2,42=5.143; p<0.01). Prolonged sleep deprivation combined with performing tasks demanding constant physical effort causes long-lasting (over 24 hours) changes of the amplitude of low-frequency tremor changes. This phenomenon may significantly influence psychomotor performance, deteriorating the ability to perform tasks requiring movement precision.

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

This study examined the effects of 35h 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 3h intervals over a 35h sleep deprivation period. Performance declined on all tests after about 18–20h 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.

Caffeine protects against increased risk-taking propensity during severe sleep deprivation

Previous research suggests that sleep deprivation is associated with declines in metabolic activity within brain regions important for judgement and impulse control, yet previous studies have reported inconsistent findings regarding the effects of sleep loss and caffeine on risk-taking. In this study, 25 healthy adults (21 men, four women) completed the Balloon Analog Risk Task (BART) and Evaluation of Risks (EVAR) scale at regular intervals to examine behavioral and self-reported risk-taking propensity during 75 h of continuous sleep deprivation. Participants received either four double-blind administrations of 200 mg caffeine (n=12) or indistinguishable placebo (n=13) gum bi-hourly during each of the 3 nights of sleep deprivation. No significant effects of drug group or sleep deprivation were evident on the BART or EVAR when measured at 51 h of wakefulness. However, by 75 h, the placebo group showed a significant increase in risk-taking behavior on the cost-benefit ratio and total number of exploded balloons on the BART, whereas the caffeine group remained at baseline levels. On the EVAR, several factors of self-reported risk-taking propensity, including total risk, impulsivity and risk/thrill seeking, were reduced among subjects receiving caffeine across the 3 days of sleep deprivation, but remained at baseline levels for the placebo group. These results suggest that 3 nights of total sleep deprivation led to a significant increase in behavioral risk-taking but not self-reported perception of risk-propensity. Overnight caffeine prevented this increase in risky behavior.

Twenty-four hours, or five days, of continuous sleep deprivation or experimental sleep fragmentation do not alter thirst or motivation for water reward in rats

Sleep disruption results in an increased demand for energy, which typically causes hyperphagia in an attempt to redress the energy metabolism imbalance. Therefore, experiments combining food reward and sleep disruption may underestimate the effect of sleep disruption due to their contradictory influences on behavior (for example on operant measures of attention). In contrast, water is not a central component of energy metabolism and thus thirst may not be affected by sleep disruption. However, little work has been done examining the effect of sleep disruption on thirst and motivation for water. The effect of total sleep deprivation (SD) and experimental sleep fragmentation (SF) on thirst and motivation for water was assessed. In experiment 1 (using 22 month old male Fisher-Norway rats) the amount of water consumed during a 15 min period immediately following a period of 24 h SD or SF (in which water was not available) was measured, and, in a separate session, the amount of water consumed during the 24 h of SD or SF was measured. Thereafter, the effect of 5 days SD or SF on motivation for water was assessed with the progressive ratio task (using water reward), which is widely used to assess motivation. Experiment 2 (using 6 month, and 22 month, old male Sprague- Dawley rats) followed an identical design except that the SF condition was dropped (due to a lack of any difference between the SD and SF conditions in experiment 1), and only the 6 month old rats experienced the full 5 day SD condition. Daily measurements of body weight and food consumption were recorded in experiment 2 in order to confirm previously published findings that food consumption goes up and body weight declines in sleep deprived rats. In both experiments the quantity of water rats consumed during a 15 min period immediately following the 24 h period of sleep disruption, or consumed during the 24 h period of SD or SF, did not change compared to control rats. Furthermore, 5 days of SD or SF had no effect on breakpoint in the progressive ratio task indicating that 5 days of SD or SF did not alter motivation for water reward. As previously reported, food consumption increased and body weight decreased during the 5 days of SD. in experiment 2. The findings indicate that although sleep disruption increases food consumption and decreases body weight, it does not alter thirst or motivation for water reward. Thus, water restriction is well suited for experiments examining the effect of sleep disruption on reward motivated behavioral tests in rats.

Neuropeptide‐Y and prepro‐orexin gene expression increases after continuous sleep deprivation but not sleep restriction in rats

The sleep loss is characterized by increased food intake in human and rats. However, the statement that in rats the sleep deprivation‐induced hyperphagia is followed by weight loss, suggests that the physiological factors involved are different from those proposed to human. Our objective was to investigate the sleep deprivation‐induced changes on feeding behavior and body weight by the platform technique in rats and to access the repercussions on hypothalamic expression of neuropeptides related to sleep and food intake control. Rats receiving a liquid diet were sleep deprived by the platform technique for 24, 48, 72, 96 hours and for 21 days by sleep restriction. We investigated feed behavior, body weight, and hypothalamic prepro‐orexin, neuropeptide Y, insulin receptor, agouti related peptide and POMC expression. Increased gene expression of the prepro‐orexin was closer related to sleep debit than food intake changes. Despite of unchanged body weight, rats continuously sleep deprived, but not the restricted ones, showed increases in prepro‐orexin and neuropeptide Y gene expression which can interacts to food intake augmentation during sleep deprivation.Financial support: FAPESP, CNPq and AFIP.

EFFECTS OF SLEEP DEPRIVATION ON LATERAL VISUAL ATTENTION

Sleep loss temporarily impairs vigilance and sustained attention. Because these cognitive abilities are believed to be mediated predominantly by the right cerebral hemisphere, this article hypothesized that continuous sleep deprivation results in a greater frequency of inattention errors within the left versus right visual fields. Twenty-one participants were assessed several times each day during a 40-h period of sustained wakefulness and following a night of recovery sleep. At each assessment, participants engaged in a continuous serial addition task while simultaneously monitoring a 150° visual field for brief intermittent flashes of light. Overall, omission errors were most common in the leftmost peripheral field for all sessions, and did not show any evidence of a shift in laterality as a function of sleep deprivation. Relative to rested baseline and postrecovery conditions, sleep deprivation resulted in a global increase in omission errors across all visual locations and a general decline in serial addition performance. These findings argue against the hypothesis that sleep deprivation produces lateralized deficits in attention and suggest instead that deficits in visual attention produced by sleep deprivation are global and bilateral in nature.

A quantitative model of work-related fatigue: empirical evaluations

Systematic and quantitative management of work-related fatigue within workplaces has been a challenging task due to a lack of useful tools. A previous paper provided background and development of a work-related fatigue modelling approach. The current paper outlines model evaluations using sleep deprivation experiments and recommendations of work scheduling. Previous studies have reported cumulative effects of sleep restriction (4–5 h per night) on a number of measures. Model predictions were correlated against psychomotor vigilance task lapses (r= 0.92) and reaction time responses (slowest 10%,r= 0.91) as well as sleep latency (r=-0.97). Further correlations were performed on four measures from a 64 h continuous sleep deprivation study; that is objective vigilance (r=-0.75) as well as subjective performance (r=-0.75), sleepiness (r= 0.82) and tiredness (r= 0.79). Evaluation against current scheduling recommendations illustrated consistency with the literature with the exception that forward rotation did not provide benefits over backward rotation. The results indicate that model predictions correlate well across a range of objective and subjective measures. This relationship also appears to hold for cumulative and continuous sleep deprivation protocols. Future studies will also focus on field-based evaluation.

Short-term total sleep deprivations does not selectively impair higher cortical functioning.

Previous research has shown that total sleep deprivation produces impairment in sustained attention and vigilance especially if the deprivation period is greater than 48 hours. However little is known about the effects of sleep deprivation on performance of tasks considered to be measures of higher cortical functioning such as tests of cognitive flexibility and the capacity to shift from one response set to another. One current hypothesis is that sleep deprivation of a shorter duration (34-36 hours) adversely affects higher cortical function while effects on attention and vigilance tasks are relatively mild. Performance on an intelligence test, a test of sustained attention and tests designed to measure higher cortical function were compared in a group of 29 subjects who underwent 34-36 hours of continuous sleep deprivation and 32 normal sleeping control subjects. No significant group performance differences in the hypothesized direction were noted on any measure. One night of total sleep deprivation does not appear to impair performance on tasks that are designed to assess higher cortical functioning.

Sleep loss impairs short and novel language tasks having a prefrontal focus

Most cognitive tests administered during sleep loss are well rehearsed to remove practice effects. This can introduce tedium and a loss of novelty, which may be the key to the test's subsequent sensitivity to sleep loss, and why it may need only a few minutes administration before sleep loss effects are apparent. There is little evidence to show that any of these tests are actually affected by sleep loss is given de novo, without practice, but using a non-sleep deprived control group. Although the sleep deprivation literature advocates that short, novel and stimulating tests would not be expected to be sensitive to sleep loss, recent sleep loss findings using neuropsychological tests focussing on the prefrontal cortex, indicate that such tests may challenge this maxim. Twenty healthy young adults were randomly assigned to two groups: nil sleep deprivation (control). and 36h continuous sleep deprivation (SD). Two, novel, interesting and short (6 min) language tests, known (by brain imaging) to have predominantly a PFC focus, were given, once, towards the end of SD: (i) the Haylings test--which measures the capacity to inhibit strong associations in favour of novel responses, and (ii) a variant of the word fluency test--innovation in a verb-to-noun association. Subjects were exhorted to do their best. Compared with control subjects both tasks were significantly impaired by SD. As a check on the effects on the Haylings test, a repeat study was undertaken with 30 more subjects randomly divided as before. The outcome was similar. Linguistically, sleep loss appears to interfere with novel responses and the ability to suppress routine answers.

Effects of prolonged wakefulness on cyclic alternating pattern (CAP) during sleep recovery at different circadian phases.

Two separate groups of healthy subjects aged between 20 and 30 years underwent a random sequence of two non-consecutive polysomnographic recordings under standard conditions (night basal sleep) and after continuous sleep deprivation (recovery sleep). In the first group of 6 subjects (3 males and 3 females) recovery sleep occurred in the morning (after 24 h of prior waking); in the second group of 6 subjects (3 males and 3 females) recovery sleep occurred in the night (after 36 h of prior waking). In all cases the recording time was restricted to 500 minutes. Scoring was accomplished on conventional sleep variables and on Cyclic Alternating Pattern (CAP) parameters, while statistical analysis was based on a 2 x 2 ANOVA test. Compared to the night basal conditions, total sleep time and total NREM sleep were significantly longer in night recovery sleep and shorter in morning recovery sleep, respectively. No significant differences were found for sleep latency, intra-sleep awakenings, stage 2, REM sleep, NREM stages and slow-wave sleep. Total CAP time, CAP time in slow-wave sleep and all CAP rates were significantly higher in morning recovery sleep and lower in night recovery sleep. The enhanced amounts of CAP time and CAP rates during morning recovery sleep may be the outcome of two opposite forces, i.e. high sleep pressure versus maximum wake propensity. In contrast, the lower values of CAP during night recovery sleep suggest an in-phase associations between strong sleep pressure and the circadian clock.