Effects of sleep deprivation on memory in mice: role of state-dependent learning

Study Objectives:

A considerable amount of experimental evidence suggests that sleep plays a critical role in learning/memory processes. In addition to paradoxical sleep, slow wave sleep is also reported to be involved in the consolidation process of memories. Additionally, sleep deprivation can induce other behavioral modifications, such as emotionality and alternations in locomotor activity in rodents. These sleep deprivation-induced alterations in the behavioral state of animals could produce state-dependent learning and contribute, at least in part, to the amnestic effects of sleep deprivation. The aim of the present study was to examine the participation of state-dependent learning during memory impairment induced by either paradoxical sleep deprivation (PSD) or total sleep deprivation (TSD) in mice submitted to the plus-maze discriminative avoidance or to the passive avoidance task.

Design:

Paradoxical sleep deprivation (by the multiple platform method) and total sleep deprivation (by the gentle handling method) were applied to animals before training and/or testing.

Conclusions:

Whereas pre-training or pre-test PSD impaired retrieval in both memory models, pre-training plus pre-test PSD counteracted this impairment. For TSD, pre-training, pre-test, and pre-training plus pre-test TSD impaired retrieval in both models. Our data demonstrate that PSD- (but not TSD-) memory deficits are critically related to state-dependent learning.

Citation:

Patti CL; Zanin KA; Sanday L; Kameda SR; Fernandes-Santos L; Fernandes HA; Andersen ML; Tufik S; Frussa-Filho R. Effects of sleep deprivation on memory in mice: role of state-dependent learning. SLEEP 2010;33(12):1669-1679.     

Sleep Deprivation in Pigeons and Rats Using Motion Detection

Study Objectives:

Forced sleep deprivation results in substantial behavioral and physiologic effects in mammals. The disk-over-water (DOW) method produces a syndrome characterized by increased energy expenditure and a robust preferentially rapid-eye-movement sleep rebound upon recovery or eventual death after several weeks of sleep deprivation. The DOW has been used successfully only in rats. This paper presents a method to enforce long-term controlled sleep deprivation across species and to compare its effects in rats and pigeons.

Design and Intervention:

A conveyor was substituted for the DOW disk. Behavior rather than electroencephalography was used to trigger arousal stimuli, as in gentle-handling deprivation. Rats and pigeons were deprived using this apparatus, and the were compared with each other and with published reports.

Measurements and Results:

The physiologic consequences and recovery sleep in rats were like those published for DOW rats. Magnitude of sleep loss and recovery patterns in pigeons were similar to those seen in rats, but expected symptoms of the sleep deprivation syndrome were absent in pigeons. The use of a motion trigger allowed us to measure and, thus, to assess the quality and impact of the procedure.

Conclusion:

Prolonged and controlled sleep deprivation can be enforced using automated motion detection and a conveyor-over-water system. Pigeons and rats, deprived of sleep to the same extent, showed similar patterns of recovery sleep, but pigeons did not exhibit the hyperphagia, weight loss, and debilitation seen in rats.

Citation:

Newman SM; Paletz EM; Obermeyer WH; Benca RM. Sleep Deprivation In Pigeons And Rats Using Motion Detection. SLEEP 2009;32(10):1299-1312.     

Changes in Serum TSH and Free T4 during Human Sleep Restriction

Study Objectives:

To examine whether recurrent sleep restriction is accompanied by changes in measures of thyroid function.

Design:

Two-period crossover intervention study.

Setting:

University clinical research center and sleep laboratory.

Participants:

11 healthy volunteers (5F/6M) with a mean (± SD) age of 39 ± 5 y and BMI 26.5 ± 1.5 kg/m².

Intervention:

Randomized exposure to 14 days of sedentary living with ad libitum food intake and 5.5- vs. 8.5-h overnight sleep opportunity.

Measurements and Results:

Serum thyroid-stimulating hormone (TSH) and free thyroxine (T4) were measured at the end of each intervention. Partial sleep restriction was accompanied by a modest but statistically significant reduction in TSH and free T4, seen mainly in the female participants of the study.

Conclusions:

Compared to the well-known rise in TSH and thyroid hormone concentrations during acute sleep loss, tests obtained after 14 days of partial sleep restriction did not show a similar activation of the human thyroid axis.

Citation:

Kessler L; Nedeltcheva A; Imperial J; Penev PD. Changes in serum TSH and free T4 during human sleep restriction. SLEEP 2010;33(8):1115-1118.     

Narcolepsy with Long Sleep Time: A Specific Entity?

Background:

The classical narcolepsy patient reports intense feelings of sleepiness (with/out cataplexy), normal or disrupted nighttime sleep, and takes short and restorative naps. However, with long-term monitoring, we identified some narcoleptics resembling patients with idiopathic hypersomnia.

Objective:

To isolate and describe a new subtype of narcolepsy with long sleep time).

Setting:

University Hospital

Design:

Controlled, prospective cohort

Participants:

Out of 160 narcoleptics newly diagnosed within the past 3 years, 29 (18%) had a long sleep time (more than 11 h/24 h). We compared narcoleptics with (n = 23) and without (n = 29) long sleep time to 25 hypersomniacs with long sleep time and 20 healthy subjects.

Intervention:

Patients and controls underwent face-to face interviews, questionnaires, human leukocyte antigen (HLA) genotype, an overnight polysomnography, multiple sleep latency tests, and 24-h ad libitum sleep monitoring.

Results:

Narcoleptics with long sleep time had a similar disease course and similar frequencies of cataplexy, sleep paralysis, hallucinations, multiple sleep onset in REM periods, short mean sleep latencies, and HLA DQB1*0602 positivity as narcoleptics with normal sleep time did. However, they had longer sleep time during 24 h, and higher sleep efficiency, lower Epworth Sleepiness Scale scores, and reported their naps were more often unrefreshing. Only 3/23 had core narcolepsy (HLA and cataplexy positive).

Conclusions:

The subgroup of narcoleptics with a long sleep time comprises 18% of narcoleptics. Their symptoms combine the disabilities of both narcolepsy (severe sleepiness) and idiopathic hypersomnia (long sleep time and unrefreshing naps). Thus, they may constitute a group with multiple arousal system dysfunctions.

Citation:

Vernet C; Arnulf I. Narcolepsy with long sleep time: a specific entity? SLEEP 2009;32(9):1229-1235.     

The Impact of Partial Sleep Deprivation on Moral Reasoning in Military Officers

Study Objectives:

The present study explores the impact of long-term partial sleep deprivation on the activation of moral justice schemas, which are suggested to play a prominent role in moral reasoning and the formation of moral judgments and behavior.

Design:

Participants judged 5 dilemmas in rested and partially sleep deprived condition, in a counterbalanced design.

Setting:

In classroom and field exercises at the Norwegian Naval Academy and the Norwegian Army Academy.

Participants:

Seventy-one Norwegian naval and army officer cadets.

Measurements and Results:

The results showed that the officers'' ability to conduct mature and principally oriented moral reasoning was severely impaired during partial sleep deprivation compared to the rested state. At the same time, the officers became substantially more rules-oriented in the sleep deprived condition, while self-oriented moral reasoning did not change. Interaction effects showed that those officers who displayed high levels of mature moral reasoning (n = 24) in the rested condition, lost much of this capacity during sleep deprivation in favor of a strong increase in rules-oriented moral reasoning as well as self-orientation. Conversely, officers at low levels of mature moral reasoning in rested condition (n = 23) were unaffected by sleep deprivation.

Conclusions:

The present data show that long-term partial sleep deprivation has an impact on the activation of moral justice schemas, and consequently on the ability to make moral justice judgments.

Citation:

Olsen OK; Pallesen S; Eid J. The impact of partial sleep deprivation on moral reasoning in military officers. SLEEP 2010;33(8):1086-1090.     

Dopamine Transporter Regulation during Four Nights of REM Sleep Deprivation Followed by Recovery – An in vivo Molecular Imaging Study in Humans

Objectives:

To assess the influence of total or selective REM sleep deprivation on the dopamine transporter (DAT) densities and sleep patterns of healthy volunteers.

Design:

Prospective study.

Setting:

Evaluation of polysomnography recordings and DAT density after 4 nights of selective REM sleep deprivation followed by 3 nights of sleep recovery compared to a control group and a group that was subjected to 2 nights of total sleep deprivation. Single positron emission computed tomography and [^99mTc]TRODAT-1 were used to assess the cerebral DAT density in the striatum at baseline, after REM sleep deprivation and total sleep deprivation as well as after sleep recovery. Blood was collected daily to examine prolactin and estradiol levels, which were correlated with dopaminergic activity.

Patients or Participants:

Thirty healthy male volunteers ranging from 19 to 29 years of age were randomly assigned to one of three experimental groups after giving written informed consent (10 non-sleep deprived, 10 total sleep deprived, and 10 REM sleep deprived).

Measurements and Results:

Four nights of REM sleep deprivation and 2 nights of total sleep deprivation induced distinct and heterogeneous patterns of sleep recovery. No significant modulation of DAT availability was observed within groups. In the recovery nights, changes in cortisol, prolactin and estradiol concentrations were significantly correlated with specific sleep stages in the total and REM sleep deprived groups. In addition, DAT density was positively correlated with estradiol concentration and inversely associated with SWS latency only after total sleep deprivation.

Conclusion:

Our study demonstrates that although sleep deprivation did not promote significant alterations in DAT density within the striatum, there were significant correlations among transporter availability, hormonal concentrations and sleep parameters.

Citation:

Martins, RCS; Andersen ML; Garbuio SA; Bittencourt LR: Guindalini C; Shih MC; Hoexter MQ; Bressan RA; Castiglioni MLV; Tufik S. Dopamine transporter regulation during four nights of REM sleep deprivation followed by recovery – an in vivo molecular imaging study in humans. SLEEP 2010;33(2):243-251.     

Slow Wave Sleep and REM Sleep Awakenings Do Not Affect Sleep Dependent Memory Consolidation

Study Objectives:

The effects of REM sleep and slow wave sleep (SWS) deprivation on sleep-dependent motor and declarative memory consolidation.

Design:

Randomized, within-subject, cross-over study

Setting:

Weekly (women: monthly) sleep laboratory visits, with retest 60 hours later

Participants:

Twelve healthy subjects (6 men) aged between 20 and 30 years

Interventions:

REM sleep deprivation, SWS deprivation, or undisturbed sleep

Measurements and Results:

We deprived subjects once each of REM sleep and SWS, and once let them sleep undisturbed through the night. After each night, we tested declarative and procedural memory consolidation. We tested memory performance by a verbal paired associate task and a sequential finger-tapping task at 21:00 on the study night and again 60 hours later. Although REM sleep and SWS awakenings led to a significant reduction of the respective sleep stages, memory consolidation remained unaffected. We also found a significant correlation between the declarative task and sleep spindles in the undisturbed condition, especially the sleep spindles in the first third of the night.

Conclusion:

We suggest that word-pair learning relies on stage 2 sleep spindles and requires little SWS. Their sleep dependent consolidation is not affected by SWS deprivation. Simple motor tasks may either be consolidated in stage 2 sleep or depend on only small amounts of REM sleep. Their sleep dependent consolidation is not influenced by REM sleep deprivation.

Citation:

Genzel L; Dresler M; Wehrle R; Grözinger M; Steiger A. Slow wave sleep and REM sleep awakenings do not affect sleep dependent memory consolidation. SLEEP 2009;32(3):302–310.     

Effects of Modafinil on the Sleep EEG Depend on Val158Met Genotype of COMT

Study Objectives:

Modafinil may promote wakefulness by increasing cerebral dopaminergic neurotransmission, which importantly depends on activity of catechol-O-methyltransferase (COMT) in prefrontal cortex. The effects of modafinil on sleep homeostasis in humans are unknown. Employing a novel sleep-pharmacogenetic approach, we investigated the interaction of modafinil with sleep deprivation to study dopaminergic mechanisms of sleep homeostasis.

Design:

Placebo-controlled, double-blind, randomized crossover study.

Setting:

Sleep laboratory in temporal isolation unit.

Participants:

22 healthy young men (23.4 ± 0.5 years) prospectively enrolled based on genotype of the functional Val158Met polymorphism of COMT (10 Val/Val and 12 Met/Met homozygotes).

Interventions:

2 × 100 mg modafinil and placebo administered at 11 and 23 hours during 40 hours prolonged wakefulness.

Measurements and Results:

Subjective sleepiness and EEG markers of sleep homeostasis in wakefulness and sleep were equally affected by sleep deprivation in Val/Val and Met/Met allele carriers (placebo condition). Modafinil attenuated the evolution of sleepiness and EEG 5-8 Hz activity during sleep deprivation in both genotypes. In contrast to caffeine, modafinil did not reduce EEG slow wave activity (0.75-4.5 Hz) in recovery sleep, yet specifically increased 3.0-6.75 Hz and > 16.75 Hz activity in NREM sleep in the Val/Val genotype of COMT.

Conclusions:

The Val158Met polymorphism of COMT modulates the effects of modafinil on the NREM sleep EEG in recovery sleep after prolonged wakefulness. The sleep EEG changes induced by modafinil markedly differ from those of caffeine, showing that pharmacological interference with dopaminergic and adenosinergic neurotransmission during sleep deprivation differently affects sleep homeostasis.

Citation:

Bodenmann S; Landolt HP. Effects of modafinil on the sleep EEG depend on Val158Met genotype of COMT. SLEEP 2010;33(8):1027-1035.     

Chronically Restricted Sleep Leads to Depression-Like Changes in Neurotransmitter Receptor Sensitivity and Neuroendocrine Stress Reactivity in Rats

Study Objectives:

Frequently disrupted and restricted sleep is a common problem for many people in our Western society. In the long run, insufficient sleep may have repercussions for health and may sensitize individuals to psychiatric diseases. In this context, we applied an animal model of chronic sleep restriction to study effects of sleep loss on neurobiological and neuroendocrine systems that have been implied in the pathophysiology of depression, particularly the serotonergic system and the hypothalamic-pituitary-adrenal (HPA) axis.

Design:

Adult rats were exposed to a schedule of chronic partial sleep deprivation allowing them only 4 h of sleep per day. Sleep restriction was achieved by placing the animals in slowly rotating drums. To examine the regulation and reactivity of the HPA axis, blood samples were collected to measure adrenocorticotropin (ACTH) and corticosterone (CORT) responses.

Measurements and Results:

While one day of restricted sleep had no significant effect on HPA axis stress reactivity, sleep restriction for a week caused a blunted pituitary ACTH response in a conditioned fear paradigm. Despite this lower ACTH response, adrenal CORT release was normal. The blunted pituitary response may be related to reduced sensitivity of serotonin-1A receptors and/or receptors for corticotropin-releasing hormone (CRH), since sleep restricted rats showed similar reductions in ACTH release to direct pharmacological stimulation with a serotonin-1A agonist or CRH.

Conclusions:

Chronic sleep restriction may lead to changes in neurotransmitter receptor systems and neuroendocrine reactivity in a manner similar to that seen in depression. This experimental study thus supports the hypothesis that disrupted and restricted sleep may contribute to the symptomatology of psychiatric disorders.

Citation:

Novati A; Roman V; Cetin T; Hagewoud R; den Boer JA; Luiten PGM; Meerlo P. Chronically restricted sleep leads to depression-like changes in neurotransmitter receptor sensitivity and neuroendocrine stress reactivity in rats. SLEEP 2008;31(11):1579–1585.     

A time for learning and a time for sleep: the effect of sleep deprivation on contextual fear conditioning at different times of the day

Study Objectives:

Sleep deprivation negatively affects memory consolidation, especially in the case of hippocampus-dependent memories. Studies in rodents have shown that 5 hours of sleep deprivation immediately following footshock exposure selectively impairs the formation of a contextual fear memory. In these studies, both acquisition and subsequent sleep deprivation were performed in the animals'' main resting phase. However, in everyday life, subjects most often learn during their active phase.

Design:

Here we examined the effects of sleep deprivation on memory consolidation for contextual fear in rats when the task was performed at different times of the day, particularly, at the beginning of the resting phase or right before the onset of the active phase.

Measurements and Results:

Results show that sleep deprivation immediately following training affects consolidation of contextual fear, independent of time of training. However, in the resting phase memory consolidation was impaired by 6 hours of posttraining sleep deprivation, whereas, in the active phase, the impairment was only seen after 12 hours of sleep deprivation. Since rats sleep at least twice as much during the resting phase compared with the active phase, these data suggest that the effect of sleep deprivation depends on the amount of sleep that was lost. Also, control experiments show that effects of sleep deprivation were not related to the amount of stimulation the animals received and were therefore not likely an indirect effect of the sleep-deprivation method.

Conclusion:

These results support the notion that sleep immediately following acquisition, independent of time of day, promotes memory consolidation and that sleep deprivation may disrupt this process depending on the amount of sleep that is lost.

Citation:

Hagewoud R; Whitcomb SN; Heeringa AN; Havekes R; Koolhaas JM; Meerlo P. A time for learning and a time for sleep: the effect of sleep deprivation on contextual fear conditioning at different times of the day. SLEEP 2010;33(10):1315-1322.     

The influence of sleep deprivation and obesity on DNA damage in female Zucker rats

OBJECTIVE:

The aim of this study was to evaluate overall genetic damage induced by total sleep deprivation in obese, female Zucker rats of differing ages.

METHOD:

Lean and obese Zucker rats at 3, 6, and 15 months old were randomly distributed into two groups for each age group: home-cage control and sleep-deprived (N = 5/group). The sleep-deprived groups were deprived sleep by gentle handling for 6 hours, whereas the home-cage control group was allowed to remain undisturbed in their home-cage. At the end of the sleep deprivation period, or after an equivalent amount of time for the home-cage control groups, the rats were brought to an adjacent room and decapitated. The blood, brain, and liver tissue were collected and stored individually to evaluate DNA damage.

RESULTS:

Significant genetic damage was observed only in 15-month-old rats. Genetic damage was present in the liver cells from sleep-deprived obese rats compared with lean rats in the same condition. Sleep deprivation was associated with genetic damage in brain cells regardless of obesity status. DNA damage was observed in the peripheral blood cells regardless of sleep condition or obesity status.

CONCLUSION:

Taken together, these results suggest that obesity was associated with genetic damage in liver cells, whereas sleep deprivation was associated with DNA damage in brain cells. These results also indicate that there is no synergistic effect of these noxious conditions on the overall level of genetic damage. In addition, the level of DNA damage was significantly higher in 15-month-old rats compared to younger rats.     

The Variable Response-Stimulus Interval Effect and Sleep Deprivation: An Unexplored Aspect of Psychomotor Vigilance Task Performance

Study Objectives:

The Psychomotor Vigilance Task (PVT) contains variable response-stimulus intervals (RSI). Our goal is to investigate the effect of RSI on performance to determine whether sleep deprivation affects the ability to attend to events across seconds and whether this effect is independent of impairment in sustaining attention across minutes, as measured by time on task.

Design:

A control group following their normal sleep routines and 3 groups exposed to 54 hours of total sleep deprivation performed a 10-minute PVT every 6 hours for 9 total test runs.

Setting:

Sleep deprivation occurred in a sleep laboratory with continuous behavioral monitoring; the control group took the PVT at home.

Subjects:

Eighty-four healthy sleepers (68 sleep deprivation, 16 controls; 22 women; aged 18-35 years).

Measurements and Results:

Across groups, as the RSI increased from 2 to 10 seconds, mean RT was reduced by 69 milliseconds (main effect of RSI, P < 0.001). There was no interaction between the sleep deprivation and RSI effects. As expected, there was a significant interaction of sleep deprivation and time on task for mean RT (P = 0.002). Time on task and RSI effects were independent. Parallel analyses of percentage of lapses and percentage of false starts produced similar results.

Conclusions:

We demonstrate that the cognitive mechanism of attention responsible for response preparation across seconds is distinct from that for maintaining attention to task performance across minutes. Of these, only vigilance across minutes is degraded by sleep deprivation. Theories of sleep deprivation should consider how this pattern of spared and impaired aspects of attention may affect real-world performance.

Citation:

Tucker AM; Basner RC; Stern Y; Rakitin BC. The variable response-stimulus interval effect and sleep deprivation: an unexplored aspect of psychomotor vigilance task performance. SLEEP 2009;32(10):1393-1395.     

Sleep Deprivation Impairs the Accurate Recognition of Human Emotions

Study Objectives:

Investigate the impact of sleep deprivation on the ability to recognize the intensity of human facial emotions.

Design:

Randomized total sleep-deprivation or sleep-rested conditions, involving between-group and within-group repeated measures analysis.

Setting:

Experimental laboratory study.

Participants:

Thirty-seven healthy participants, (21 females) aged 18–25 y, were randomly assigned to the sleep control (SC: n = 17) or total sleep deprivation group (TSD: n = 20).

Interventions:

Participants performed an emotional face recognition task, in which they evaluated 3 different affective face categories: Sad, Happy, and Angry, each ranging in a gradient from neutral to increasingly emotional. In the TSD group, the task was performed once under conditions of sleep deprivation, and twice under sleep-rested conditions following different durations of sleep recovery. In the SC group, the task was performed twice under sleep-rested conditions, controlling for repeatability.

Measurements and Results:

In the TSD group, when sleep-deprived, there was a marked and significant blunting in the recognition of Angry and Happy affective expressions in the moderate (but not extreme) emotional intensity range; differences that were most reliable and significant in female participants. No change in the recognition of Sad expressions was observed. These recognition deficits were, however, ameliorated following one night of recovery sleep. No changes in task performance were observed in the SC group.

Conclusions:

Sleep deprivation selectively impairs the accurate judgment of human facial emotions, especially threat relevant (Anger) and reward relevant (Happy) categories, an effect observed most significantly in females. Such findings suggest that sleep loss impairs discrete affective neural systems, disrupting the identification of salient affective social cues.

Citation:

van der Helm E; Gujar N; Walker MP. Sleep deprivation impairs the accurate recognition of human emotions. SLEEP 2010;33(3):335-342.     

Effects of Sleep Deprivation on Dissociated Components of Executive Functioning

Study Objectives:

We studied the effects of sleep deprivation on executive functions using a task battery which included a modified Sternberg task, a probed recall task, and a phonemic verbal fluency task. These tasks were selected because they allow dissociation of some important executive processes from non-executive components of cognition.

Design:

Subjects were randomized to a total sleep deprivation condition or a control condition. Performance on the executive functions task battery was assessed at baseline, after 51 h of total sleep deprivation (or no sleep deprivation in the control group), and following 2 nights of recovery sleep, at fixed time of day (11:00). Performance was also measured repeatedly throughout the experiment on a control task battery, for which the effects of total sleep deprivation had been documented in previously published studies.

Setting:

Six consecutive days and nights in a controlled laboratory environment with continuous behavioral monitoring.

Participants:

Twenty-three healthy adults (age range 22–38 y; 11 women). Twelve subjects were randomized to the sleep deprivation condition; the others were controls.

Results:

Performance on the control task battery was considerably degraded during sleep deprivation. Overall performance on the modified Sternberg task also showed impairment during sleep deprivation, as compared to baseline and recovery and compared to controls. However, two dissociated components of executive functioning on this task—working memory scanning efficiency and resistance to proactive interference—were maintained at levels equivalent to baseline. On the probed recall task, resistance to proactive interference was also preserved. Executive aspects of performance on the phonemic verbal fluency task showed improvement during sleep deprivation, as did overall performance on this task.

Conclusion:

Sleep deprivation affected distinct components of cognitive processing differentially. Dissociated non-executive components of cognition in executive functions tasks were degraded by sleep deprivation, as was control task performance. However, the executive functions of working memory scanning efficiency and resistance to proactive interference were not significantly affected by sleep deprivation, nor were dissociated executive processes of phonemic verbal fluency performance. These results challenge the prevailing view that executive functions are especially vulnerable to sleep loss. Our findings also question the idea that impairment due to sleep deprivation is generic to cognitive processes subserved by attention.

Citation:

Tucker AM; Whitney P; Belenky G; Hinson JM; Van Dongen HPA. Effects of sleep deprivation on dissociated components of executive functioning. SLEEP 2010;33(1):47-57.     

Banking Sleep: Realization of Benefits During Subsequent Sleep Restriction and Recovery

Objective:

Determine whether sleep extension (a) improves alertness and performance during subsequent sleep restriction and (b) impacts the rate at which alertness and performance are restored by post-restriction recovery sleep.

Design:

Participants were randomly assigned to an Extended (10 h time in bed [TIB]) or Habitual TIB [mean (SD) hours = 7.09 (0.7)] sleep group for one week, followed by 1 Baseline (10 hours or habitual TIB), 7 Sleep Restriction (3 h TIB), and 5 Recovery Sleep nights (8 h TIB). Performance and alertness tests were administered hourly between 08:00–18:00 during all in-laboratory phases of the study.

Setting:

Residential sleep/performance testing facility.

Participants:

Twenty-four healthy adults (ages 18–39) participated in the study.

Interventions:

Extended vs. habitual sleep durations prior to sleep restriction.

Results:

Psychomotor vigilance task (PVT) lapses were more frequent and modified maintenance of wakefulness (MWT) sleep latency was shorter in the Habitual group than in the Extended group across the sleep restriction phase. During the Recovery phase, PVT speed rebounded faster (and PVT lapsing recovered significantly after the first night of recovery sleep) in the Extended group. No group differences in subjective sleepiness were evident during any phase of the study.

Conclusion:

The extent to which sleep restriction impairs objectively measured alertness and performance, and the rate at which these impairments are subsequently reversed by recovery sleep, varies as a function of the amount of nightly sleep obtained prior to the sleep restriction period. This suggests that the physiological mechanism(s) underlying chronic sleep debt undergo long-term (days/weeks) accommodative/adaptive changes.

Citation:

Rupp TL; Wesensten NJ; Bliese PD; Balkin TJ. Banking sleep: realization of benefits during subsequent sleep restriction and recovery. SLEEP 2009;32(3):311–321.     

Enhancing Slow Wave Sleep with Sodium Oxybate Reduces the Behavioral and Physiological Impact of Sleep Loss

Study Objectives:

To investigate whether enhancement of slow wave sleep (SWS) with sodium oxybate reduces the impact of sleep deprivation.

Design:

Double-blind, parallel group, placebo-controlled design

Setting:

Sleep research laboratory

Participants:

Fifty-eight healthy adults (28 placebo, 30 sodium oxybate), ages 18-50 years.

Interventions:

A 5-day protocol included 2 screening/baseline nights and days, 2 sleep deprivation nights, each followed by a 3-h daytime (08:00-11:00) sleep opportunity and a recovery night. Sodium oxybate or placebo was administered prior to each daytime sleep period. Multiple sleep latency test (MSLT), psychomotor vigilance test (PVT), Karolinska Sleepiness Scale (KSS), and Profile of Mood States were administered during waking hours.

Measurements and Results:

During daytime sleep, the sodium oxybate group had more SWS, more EEG spectral power in the 1-9 Hz range, and less REM. Mean MSLT latency was longer for the sodium oxybate group on the night following the first daytime sleep period and on the day following the second day sleep period. Median PVT reaction time was faster in the sodium oxybate group following the second day sleep period. The change from baseline in SWS was positively correlated with the change in MSLT and KSS. During recovery sleep the sodium oxybate group had less TST, SWS, REM, and slow wave activity (SWA) than the placebo group.

Conclusions:

Pharmacological enhancement of SWS with sodium oxybate resulted in a reduced response to sleep loss on measures of alertness and attention. In addition, SWS enhancement during sleep restriction appears to result in a reduced homeostatic response to sleep loss.

Citation:

Walsh JK; Hall-Porter JM; Griffin KS; Dodson ER; Forst EH; Curry DT; Eisenstein RD; Schweitzer PK. Enhancing slow wave sleep with sodium oxybate reduces the behavioral and physiological impact of sleep loss. SLEEP 2010;33(9):1217-1225.     

Sleep deprivation and interference by emotional distracters

Study Objectives:

We determined if sleep deprivation would amplify the effect of negative emotional distracters on working memory.

Design:

A crossover design involving 2 functional neuroimaging scans conducted at least one week apart. One scan followed a normal night of sleep and the other followed 24 h of sleep deprivation. Scanning order was counterbalanced across subjects.

Setting:

The study took place in a research laboratory.

Participants:

24 young, healthy volunteers with no history of any sleep, psychiatric, or neurologic disorders.

Interventions:

N/A

Measurements and Results:

Study participants were scanned while performing a delayed-response working memory task. Two distracters were presented during the maintenance phase, and these differed in content: highly arousing, negative emotional scenes; low-arousing, neutral scenes; and digitally scrambled versions of the pictures. Irrespective of whether volunteers were sleep deprived, negative emotional (relative to neutral) distracters elicited greater maintenance-related activity in the amygdala, ventrolateral prefrontal cortex, and fusiform gyri, while concurrently depressing activity in cognitive control regions. Individuals who maintained or increased distracter-related amygdala activation after sleep deprivation showed increased working memory disruptions by negative emotional distracters. These individuals also showed reduced functional connectivity between the amygdala and the ventromedial and dorsolateral prefrontal cortices, regions postulated to mediate cognitive control against emtional distraction.

Conclusions:

Increased distraction by emotional stimuli following sleep deprivation is accompanied by increases in amygdala activation and reduced functional connectivity between the amygdala and prefrontal cognitive control regions. These findings shed light on the neural basis for interindividual variation in how negative emotional stimuli might distract sleep deprived persons.

Citation:

Chuah LYM; Dolcos F; Chen AK; Zheng H; Parimal S; Chee MWL. Sleep deprivation and interference by emotional distracters. SLEEP 2010;33(10):1305-1313.     

Rapid eye movement sleep deprivation contributes to reduction of neurogenesis in the hippocampal dentate gyrus of the adult rat

Study Objectives:

The dentate gyrus (DG) of the adult hippocampus contains progenitor cells, which have potential to differentiate into neurons. Previously we reported that 96 hours of total sleep deprivation reduces neurogenesis in the DG of adult rats. Loss of either non-rapid eye movement (NREM) or rapid eye movement (REM) sleep could have contributed to the effect of total sleep deprivation. The present study assessed the effect of 4 days of REM sleep deprivation (REMD) on neurogenesis.

Design:

REMD was achieved by brief treadmill movement initiated by automatic online detection of REM sleep. A yoked-control (YC) rat was placed in the same treadmill and experienced the identical movement regardless the stage of the sleep-wake cycle. The thymidine analog 5- bromo- 2′- deoxy-uridine and the intrinsic proliferation marker, Ki-67, were both used to label proliferating cells.

Setting:

Basic neurophysiology laboratory.

Participants:

Male Sprague-Dawley male rats (300 – 320 g)

Results:

REM sleep was reduced by 85% in REMD rats and by 43% in YC, compared with cage control animals and by 79% in REMD rats compared with YC. NREM sleep and slow wave activity within NREM did not differ in REMD and YC groups. Cell proliferation was reduced by 63 % in REMD compared with YC rats, and by 82% and 51%, respectively, in REMD and YC rats compared with cage controls. Across all animals, cell proliferation exhibited a positive correlation with the percentage of REM sleep (r = 0.84, P < 0.001). Reduced cell proliferation in REMD rats was confirmed with the intrinsic proliferation marker, Ki-67. REMD also reduced the percentage of proliferating cells that later expressed a mature neuronal marker.

Conclusions:

The present findings support a hypothesis that REM sleep-associated processes facilitate proliferation of granule cells in the adult hippocampal DG.

Citation:

Guzman-Marin R; Suntsova N; Bashir T; Nienhuis R; Szymusiak R; McGinty D. Rapid eye movement sleep deprivation contributes to reduction of neurogenesis in the hippocampal dentate gyrus of the adult rat. SLEEP 2008;31(2):167–175.     

Socializing by Day May Affect Performance by Night: Vulnerability to Sleep Deprivation is Differentially Mediated by Social Exposure in Extraverts vs Introverts

Study Objectives:

To examine the effects of socially enriched versus socially impoverished environments on performance and alertness decline during sleep deprivation in extraverts versus introverts.

Design:

Participants (n = 29 men, n = 19 women) were assigned to socially enriched (n = 24; 13 introverts, 11 extraverts) or socially impoverished (n = 24; 12 introverts, 12 extraverts) conditions (activities matched) for 12 hours (1000–2200) on Day 1 followed by 22 hours of sleep deprivation (2200-2000; 36 h awake total), monitored by actigraphy. The median split of volunteers'' Eysenck Extraversion scores was used for extravert/introvert categorization. The Psychomotor Vigilance Task (PVT), modified Maintenance of Wakefulness Test (MWT), and Stanford Sleepiness Scale (SSS) were administered every 2 hours throughout. PVT speed, transformed lapses, modified MWT sleep-onset latency, and SSS were analyzed using mixed-model analyses of variance, with covariates of age and total actigraphic activity during enrichment or impoverishment.

Setting:

Residential sleep/performance testing facility.

Participants:

Forty-eight healthy adults (aged 18–39).

Interventions:

Twelve hours of socially enriched or isolated environments in extraverts and introverts prior to sleep deprivation.

Results

Social experience interacted with personality type to affect alertness and vigilance. Social enrichment, as compared with social impoverishment, was associated with more PVT lapses at 04:00 overall. Similarly, following social enrichment, PVT speed was significantly slower among extraverts than among introverts during sleep deprivation, but no personality-group differences emerged following social impoverishment. MWT sleep latency and SSS subjective sleepiness did not show significant personality or social-condition effects during sleep deprivation.

Conclusions:

The effect of social exposure on vulnerability or resiliency to sleep deprivation was modulated by introversion and extraversion. Extraverts exposed to social environments were more vulnerable to subsequent sleep deprivation than were introverts.

Citation:

Rupp TL; Killgore WDS; Balkin TJ. Socializing by day may affect performance by night: vulnerability to sleep deprivation is differentially mediated by social exposure in extraverts vs introverts. SLEEP 2010;33(11):1475-1485.