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.     

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.     

White Matter Differences Predict Cognitive Vulnerability to Sleep Deprivation

Objectives:

In other disciplines, white matter (WM) differences have been linked to cognitive impairments. This study sets out to clarify whether similar microstructural differences in WM tracts predict a person''s cognitive vulnerability to the effects of total sleep deprivation (TSD).

Design:

Participants completed a simple visual-motor task both before and after 24 h of TSD. Using a median split on the percent change in accuracy from pre-TSD to post-TSD, participants were separated into susceptibility groups. A diffusion tensor MR imaging (DTI) scan was acquired from each participant, and fractional anisotropy (FA) was calculated, examined across the brain, and compared between susceptibility groups.

Setting:

University of Texas at Austin.

Participants:

Thirty-two West Point cadets (9 females, 23 males) between 19 and 25 years of age.

Results:

Participant susceptibility to TSD was correlated with lower FA values in multiple regions of white matter, including the genu of corpus callosum and ascending and longitudinal white matter pathways. Significantly higher FA values in those less vulnerable to TSD, indicating increased neural connectivity and WM organization, may moderate the cognitive effects of sleep deprivation.

Conclusions:

Differences in distributed WM pathways reflect, and may contribute to, a person''s ability to function effectively when sleep deprived. The widespread nature of this effect supports previous views that TSD has a global effect on brain functioning.

Citation:

Rocklage M; Williams V; Pacheco J; Schnyer DM. TitleTitleTitle. SLEEP 2009;32(8):1100-1103.     

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.     

Sleep Homeostasis During Repeated Sleep Restriction and Recovery: Support from EEG Dynamics

Study Objectives:

Sleep reduction normally causes a homeostatic response during subsequent recovery sleep, but this does not seem to be true for repeated partial sleep loss. The aim of the present study was to test the response to repeated partial sleep loss through detailed focus on spectral data and parts of sleep.

Design:

The experiment involved 4 h of sleep across 5 days in the laboratory (partial sleep deprivation [PSD]), followed by 3 days of recovery sleep. PSD was achieved through a delayed bedtime. Nine individuals participated. To avoid “laboratory monotony,” subjects were permitted to leave the lab for a few hours each day.

Measurements and results:

All sleep stages and the latencies to sleep and slow wave sleep (SWS) showed a significant reduction during PSD. However, SWS and TST (total sleep time) during the first half of sleep increased gradually across days with PSD. During the first recovery sleep, SWS was significantly increased, while stage 1 and latency to stage 3 were reduced. All were back to baseline on the second night of recovery sleep. Summed spectral power during the first 3.8 h of sleep showed a gradual and robust increase (50% above baseline) in the range 1.25–7.25 Hz across days with PSD up to first recovery sleep and then returned to baseline.

Conclusions:

SWS and summed power density in a broad low-frequency band respond to repeated partial sleep deprivation in a dose-response fashion during the first 4 h sleep, apparently reflecting a robust and stable homeostatic response to sleep loss.

Citation:

Åkerstedt T; Kecklund G; Ingre M; Lekander M; Axelsson J. Sleep homeostasis during repeated sleep restriction and recovery: support from EEG dynamics. SLEEP 2009;32(2):217–222.     

Paradoxical (REM) Sleep Deprivation Causes a Large and Rapidly Reversible Decrease in Long-Term Potentiation,Synaptic Transmission,Glutamate Receptor Protein Levels,and ERK/MAPK Activation in the Dorsal Hippocampus

Study Objectives:

It has been shown that wake (W) and slow wave sleep (SWS) modulate synaptic transmission in neocortical projections. However the impact of paradoxical sleep (PS) quantities on synaptic transmission remains unknown. We examined whether PS modulated the excitatory transmission and expression of glutamate receptor subtypes and phosphorylated extracellular signal-regulated kinases (p-ERK1/2).

Design:

PS deprivation (PSD) was carried out with the multiple platforms method on adult male Sprague-Dawley rats. LTP, late-LTP, and synaptic transmission were studied in the dorsal and ventral hippocampus of controls, 75-h PSD and 150-min PS rebound (PSR). GluR1 and NR1 protein and mRNA expression were evaluated by western blot and real-time PCR. P-ERK1/2 level was quantified by western blot and immunohistochemistry.

Measurement and Results:

PSD decreased synaptic transmission and LTP selectively in dorsal CA1 and PSR rescued these deficits. PSD-induced synaptic modifications in CA1 were associated with a decrease in GluR1, NR1, and p-ERK1/2 levels in dorsal CA1 without change in GluR1 and NR1 mRNA expression. Regression analysis shows that LTP is positively correlated with both PS quantities and SWS episodes duration, whereas synaptic transmission and late-LTP are positively correlated with PS quantities and negatively correlated with SWS quantities.

Conclusions:

These findings unveil previously unrecognized roles of PSD on synaptic transmission and LTP in the dorsal, but not in the ventral, hippocampus. The fact that the decrease in protein expression of GluR1 and NR1 was not associated with a change in mRNA expression of these receptors suggests that a sleep-induced modulation of translational mechanisms occurs in dorsal CA1.

Citation:

Ravassard P; Pachoud B; Comte JC; Mejia-Perez C; Scoté-Blachon C; Gay N; Claustrat B; Touret M; Luppi PH; Salin PA. Paradoxical (REM) sleep deprivation causes a large and rapidly reversible decrease in long-term potentiation, synaptic transmission, glutamate receptor protein levels, and ERK/MAPK activation in the dorsal hippocampus. SLEEP 2009;32(2):227–240.     

Donepezil Improves Episodic Memory in Young Individuals Vulnerable to the Effects of Sleep Deprivation

Study Objectives:

We investigated if donepezil, a long-acting orally administered cholinesterase inhibitor, would reduce episodic memory deficits associated with 24 h of sleep deprivation.

Design:

Double-blind, placebo-controlled, crossover study involving 7 laboratory visits over 2 months. Participants underwent 4 functional MRI scans; 2 sessions (donepezil or placebo) followed a normal night''s sleep, and 2 sessions followed a night of sleep deprivation.

Setting:

The study took place in a research laboratory.

Participants:

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

Interventions:

5 mg of donepezil was taken once daily for approximately 17 days.

Measurements and Results:

Subjects were scanned while performing a semantic judgment task and tested for word recognition outside the scanner 45 minutes later. Sleep deprivation increased the frequency of non-responses at encoding and impaired delayed recognition. No benefit of donepezil was evident when participants were well rested. When sleep deprived, individuals who showed greater performance decline improved with donepezil, whereas more resistant individuals did not benefit. Accompanying these behavioral effects, there was corresponding modulation of task-related activation in functionally relevant brain regions. Brain regions identified in relation to donepezil-induced alteration in non-response rates could be distinguished from regions relating to improved recognition memory. This suggests that donepezil can improve delayed recognition in sleep-deprived persons by improving attention as well as enhancing memory encoding.

Conclusions:

Donepezil reduced decline in recognition performance in individuals vulnerable to the effects of sleep deprivation. Additionally, our findings demonstrate the utility of combined fMRI–behavior evaluation in psychopharmacological studies.

Citation:

Chuah LYM; Chong DL; Chen AK; Rekshan WR; Tan JC; Zheng H; Chee MWL. Donepezil improves episodic memory in young individuals vulnerable to the effects of sleep deprivation. SLEEP 2009;32(8):999-1010.     

Influence of food restriction on lipid profile and spontaneous glucose levels in male rats subjected to paradoxical sleep deprivation

OBJECTIVES:

The purpose of this study was to determine the paired consequences of food restriction and paradoxical sleep deprivation on lipid profile and spontaneous glucose levels in male rats.

METHOD:

Food restriction began at weaning, with 6 g of food being provided per day, which was subsequently increased by 1 g per week until reaching 15 g per day by the eighth week. At adulthood, both rats subjected to food restriction and those fed ad libitum were exposed to paradoxical sleep deprivation for 96 h or were maintained in their home-cage groups.

RESULTS:

Animals subjected to food restriction exhibited a significant increase in high-density lipoprotein levels compared to animals that were given free access to food. After the paradoxical sleep deprivation period, the food-restricted animals demonstrated reduced concentrations of high-density lipoprotein relative to their respective controls, although the values for the food-restricted animals after sleep deprivation were still higher than those for the ad libitum group. The concentration of low-density lipoproteins was significantly increased in sleep-deprived animals fed the ad libitum diet. The levels of triglycerides, very low-density lipoproteins, and glucose in food-restricted animals were each decreased compared to both ad libitum groups.

CONCLUSION:

These results may help to illustrate the mechanisms underlying the relationship between sleep curtailment and metabolism and may suggest that, regardless of sleep deprivation, dietary restriction can minimize alterations in parameters related to cardiovascular risk.     

Chronic Caffeine Treatment Prevents Sleep Deprivation-Induced Impairment of Cognitive Function and Synaptic Plasticity

Study Objectives:

This study was undertaken to provide a detailed account of the effect of chronic treatment with a small dose of caffeine on the deleterious effects of sleep loss on brain function in rats.

Experimental Design:

We investigated the effects of chronic (4 weeks) caffeine treatment (0.3 g/L in drinking water) on memory impairment in acutely (24 h) sleep-deprived adult male Wistar rats. Sleep deprivation was induced using the modified multiple platform model. The effects of caffeine on sleep deprivation-induced hippocampus-dependent learning and memory deficits were studied by 3 approaches: learning and memory performance in the radial arm water maze task, electrophysiological recording of early long-term potentiation (E-LTP) in area CA1 of the hippocampus, and levels of memory- and synaptic plasticity-related signaling molecules after E-LTP induction.

Measurement and Results:

The results showed that chronic caffeine treatment prevented impairment of hippocampus-dependent learning, short-term memory and E-LTP of area CA1 in the sleep-deprived rats. In correlation, chronic caffeine treatment prevented sleep deprivation-associated decrease in the levels of phosphorylated calcium/calmodulin-dependent protein kinase II (P-CaMKII) during expression of E-LTP.

Conclusions:

The results suggest that long-term use of a low dose of caffeine prevents impairment of short-term memory and E-LTP in acutely sleep-deprived rats.

Citation:

Alhaider IA; Aleisa AM; Tran TT; Alzoubi KH; Alkadhi KA. Chronic caffeine treatment prevents sleep deprivation-induced impairment of cognitive function and synaptic plasticity. SLEEP 2010;33(4):437-444.     

Energy Expenditure is Affected by Rate of Accumulation of Sleep Deficit in Rats

Study Objectives:

Short sleep is a putative risk factor for obesity. However, prolonged total sleep deprivation (TSD) leads to negative energy balance and weight loss in rodents, whereas sleep-restricted humans tend to gain weight. We hypothesized that energy expenditure (V̇O₂) is influenced by the rate of accumulation of sleep deficit in rats.

Design and Intervention:

Six Sprague-Dawley rats underwent chronic sleep-restriction (CSR, 6-h sleep opportunity at ZT0-6 for 10 days) and stimulus-control protocols (CON, 12-h sleep opportunity for 10 days, matched number of stimuli) in a balanced cross-over design. Four additional rats underwent TSD (4 days). Sleep was manipulated using a motor-driven walking wheel.

Measurements and Results:

Electroencephalography, electromyography, and body temperature were measured by telemetry, and V̇O₂, by respirometry. Total sleep deficits of 55.1 ± 6.4 hours, 31.8 ± 6.8 hours, and 38.2 ± 2.3 hours accumulated over the CSR, CON, and TSD protocols, respectively. Responses to TSD confirmed previous reports of elevated V̇O₂ and body temperature. These responses were attenuated in CSR, despite a greater cumulative sleep deficit. Rate of rise of O₂ was strongly correlated with rate of accumulation of sleep deficit, above a threshold deficit of 3.6 h·day⁻¹.

Conclusion:

The change in V̇O₂ is affected by rate of accumulation of sleep deficit and not the total sleep loss accrued. Negative energy balance, observed during TSD, is strongly attenuated when brief daily sleep opportunities are available to rats (CSR), despite greater accumulated sleep deficit.

Citation:

Caron AM; Stephenson R. Energy expenditure is affected by rate of accumulation of sleep deficit in rats. SLEEP 2010;33(9):1226-1235.     

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.     

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.     

Persistent Short-Term Memory Defects Following Sleep Deprivation in a Drosophila Model of Parkinson Disease

Study Objectives:

Parkinson disease (PD) is the second most common neurodegenerative disorder in the United States. It is associated with motor deficits, sleep disturbances, and cognitive impairment. The pathology associated with PD and the effects of sleep deprivation impinge, in part, upon common molecular pathways suggesting that sleep loss may be particularly deleterious to the degenerating brain. Thus we investigated the long-term consequences of sleep deprivation on short-term memory using a Drosophila model of Parkinson disease.

Participants:

Transgenic strains of Drosophila melanogaster.

Design:

Using the GAL4-UAS system, human α-synuclein was expressed throughout the nervous system of adult flies. α-Synuclein expressing flies (αS flies) and the corresponding genetic background controls were sleep deprived for 12 h at age 16 days and allowed to recover undisturbed for at least 3 days. Short-term memory was evaluated using aversive phototaxis suppression. Dopaminergic systems were assessed using mRNA profiling and immunohistochemistry.

Measurments and Results:

When sleep deprived at an intermediate stage of the pathology, αS flies showed persistent short-term memory deficits that lasted ≥ 3 days. Cognitive deficits were not observed in younger αS flies nor in genetic background controls. Long-term impairments were not associated with accelerated loss of dopaminergic neurons. However mRNA expression of the dopamine receptors dDA1 and DAMB were significantly increased in sleep deprived αS flies. Blocking D1-like receptors during sleep deprivation prevented persistent short-term memory deficits. Importantly, feeding flies the polyphenolic compound curcumin blocked long-term learning deficits.

Conclusions:

These data emphasize the importance of sleep in a degenerating/reorganizing brain and shows that pathological processes induced by sleep deprivation can be dissected at the molecular and cellular level using Drosophila genetics.

Citation:

Seugnet L; Galvin JE; Suzuki Y; Gottschalk L; Shaw PJ. Persistent short-term memory defects following sleep deprivation in a drosophila model of parkinson disease. SLEEP 2009;32(8):984-992.     

Sleep Deprivation Specifically Impairs Short-term Olfactory Memory in Drosophila

Study Objectives:

Sleep is crucial to memory consolidation in humans and other animals; however, the effect of insufficient sleep on subsequent learning and memory remains largely elusive.

Design:

Learning and memory after 1-day sleep deprivation (slpD) was evaluated using Pavlovian olfactory conditioning in Drosophila, and locomotor activity was measured using the Drosophila Activity Monitoring System in a 12:12 light-dark cycle.

Results:

We found that slpD specifically impaired 1-h memory in wild type Canton-S flies, and this effect could persist for at least 2 h. However, alternative stresses (heat stress, oxidative stress, starvation, and rotation stress) did not result in a similar effect and left the flies’ memory intact. Mechanistic studies demonstrated that flies with either silenced transmission of the mushroom body (MB) during slpD or down-regulated cAMP levels in the MB demonstrated no slpD-induced 1-h memory impairment.

Conclusion:

We found that slpD specifically impaired 1-h memory in Drosophila, and either silencing of MB transmission during slpD or down-regulation of the cAMP level in the MB protected the flies from slpD-induced impairment.

Citation:

Li X; Yu F; Guo A. Sleep deprivation specifically impairs short-term olfactory memory in drosophila. SLEEP 2009;32(11):1417-1424.     

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.     

Comparison of Mandibular Advancement Splint and Tongue Stabilizing Device in Obstructive Sleep Apnea: A Randomized Controlled Trial

Study Objectives:

To compare the efficacy of a mandibular advancement splint (MAS) and a novel tongue stabilizing device (TSD) in the treatment of obstructive sleep apnea (OSA).

Design:

A randomized crossover design was used.

Patients:

Twenty-seven patients (20 male, 7 female), recruited from a tertiary hospital sleep clinic.

Measurements and Results:

The apnea-hypopnea index (AHI) was reduced with MAS (11.68 ± 8.94, P = 0.000) and TSD (13.15 ± 10.77, P = 0.002) compared with baseline (26.96 ± 17.17). The arousal index decreased for MAS (21.09 ± 9.27, P = 0.004) and TSD (21.9 ± 10.56, P = 0.001) compared with baseline (33.23 ± 16.41). Sixty-eight percent of patients achieved a complete or partial response with MAS, compared with 45% with TSD. The Epworth Sleepiness Scale (ESS) score was decreased with MAS (P = <0.001) and TSD (P = 0.002). Subjective improvements in snoring and quality of sleep were reported, with a better response for MAS than TSD. Compliance was poorer for TSD, and the side effect profiles of the 2 modalities were different. All patients were satisfied with MAS compared to TSD, and 91% of patients preferred the MAS.

Conclusion:

Objective testing showed the MAS and TSD had similar efficacy in terms of AHI reduction. Patients reported improvements with both devices; however, better compliance and a clear preference for MAS was apparent when both devices were offered. Longer term studies are needed to clarify the role of TSD.

Citation:

Deane SA; Cistulli PA; Ng AT; Zeng B; Petocz P; Darendeliler MA. Comparison of mandibular advancement splint and tongue stabilizing device in obstructive sleep apnea: a randomized controlled trial. SLEEP 2009;32(5):648-653.     

Cognitive Replay of Visuomotor Learning at Sleep Onset: Temporal Dynamics and Relationship to Task Performance

Study Objectives:

Studies of neural activity in animals and humans suggest that experiences are “replayed” in cortical and hippocampal networks during NREM sleep. Here, we examine whether memory reactivation in sleeping humans might also be evident within reports of concomitant subjective experience (i.e., dreaming).

Design:

Participants were trained on an engaging visuomotor learning task across a period of one or more days, and sleep onset mentation was collected at variable intervals using the “Nightcap” home-monitoring device. Verbal reports of sleep onset mentation were obtained either at the beginning of the night, or following 2 h of initial sleep.

Setting:

Data were collected in participants'' home environments, via the Nightcap monitoring system, and at The Center for Sleep and Cognition, Beth Israel Deaconess Medical Center, Boston MA.

Participants:

43 healthy, medication-free college students (16 males, age 18-25 years).

Interventions:

N/A

Measurements and Results:

The learning task exerted a powerful, direct effect on verbal reports of mentation during light NREM sleep (stages 1 and 2). On post-training nights, a full 30% of all verbal reports were related to the task. The nature of this cognitive “replay” effect was altered with increasing durations of sleep, becoming more abstracted from the original experience as time into sleep increased.

Conclusions:

These observations are interpreted in light of memory consolidation theory, and demonstrate that introspective reports can provide a valuable window on cognitive processing in the sleeping brain.

Citation:

Wamsley EJ; Perry K; Djonlagic I; Babkes Reaven L; Stickgold R. Cognitive replay of visuomotor learning at sleep onset: temporal dynamics and relationship to task performance. SLEEP 2010;33(1):59-68.     

The Effects of Sleep Deprivation on Information-Integration Categorization Performance

Background:

Sleep deprivation is a serious problem facing individuals in many critical societal roles. One of the most ubiquitous tasks facing individuals is categorization. Sleep deprivation is known to affect rule-based categorization in the classic Wisconsin Card Sorting Task, but, to date, information-integration categorization has not been examined.

Study Objectives:

To investigate the effects of sleep deprivation on information-integration category learning.

Design:

Participants performed an information-integration categorization task twice, separated by a 24-hour period, with or without sleep between testing sessions.

Participants:

Twenty-one West Point cadets participated in the sleep-deprivation group and 28 West Point cadets participated in a control group.

Measurements and Results:

Sleep deprivation led to an overall performance deficit during the second testing session—that is, whereas participants allowed to sleep showed a significant performance increase during the second testing session, Sleepless participants showed a small (but nonsignificant) performance decline during the second testing session. Model-based analyses indicated that a major contributor to the sleep-deprivation effect was the poor second-session performance of a subgroup of sleep-deprived participants who shifted from optimal information-integration strategies at the end of the first session to less-optimal rule-based strategies at the start of the second session. Sleep-deprived participants who used information-integration strategies in both sessions showed no drop in performance in the second session, mirroring the behavior of control participants.

Conclusions:

The findings suggest that the neural systems underlying information-integration strategies are not strongly affected by sleep deprivation but, rather, that the use of an information-integration strategy in a task may require active inhibition of rule-based strategies, with this inhibitory process being vulnerable to the effects of sleep deprivation.

Citation:

Maddox WT; Glass BD; Wolosin SM; Savarie ZR; Bowen C; Matthews MD; Schnyer DM. The effects of sleep deprivation on information-integration categorization performance. SLEEP 2009;32(11):1439-1448.