Psychomotor vigilance task performance during total sleep deprivation in young and postmenopausal women

The objective of this study was to investigate the effects of age on women's performance in the psychomotor vigilance task (PVT) during total sleep deprivation (SD). A total of 46 healthy women volunteered. They belonged to two age groups: young (n=34; age range 19-30 years; 12 without, and 22 with oral contraceptives (OC); early phase of the menstrual cycle) and older (n=12; age range 60-68; postmenopausal; without hormone therapy). During a 40-h total SD, the subjects performed the PVT and the Stanford Sleepiness Scale (SSS) at 2-h intervals. At baseline, the reaction speed of the young women was faster as compared to the older women (Mann-Whitney U-test p<0.01). During SD, all the PVT measures as well as the SSS scores changed similarly in the two age groups, when the baseline performance difference in favour of the young women was taken into account (area under curve analyses, Mann-Whitney U-tests n.s.). No age difference in the time course of the SD-related deterioration in PVT performance or subjective sleepiness was observed. OC use had no effects on any of the measures during SD. After recovery sleep, young women had higher subjective sleepiness scores than older women, the sleepiness scores being highest in young women not taking OCs. In conclusion, in women, aging has no effects on the amount or the time course of the decline in PVT performance caused by total SD. OC use does not significantly affect young women's PVT performance during SD in the early phase of the menstrual cycle.     

Topographic electroencephalogram changes associated with psychomotor vigilance task performance after sleep deprivation

ObjectivesThe psychomotor vigilance task (PVT) is a widely used method for the assessment of vigilance after sleep deprivation (SDEP). However, the neural basis of PVT performance during SDEP has not been fully understood. In particular, no studies have investigated the possible relation between EEG topographical changes after sleep loss and PVT performance. The aim of the present study is to assess the EEG topographic correlates of PVT performance after SDEP.MethodsDuring 40 h of SDEP, 16 healthy male subjects were evaluated in four sessions performed at the same time (11:00 a.m. and 11:00 p.m.) of the first and second day with: (a) subjective sleepiness recordings by means of the Karolinska Sleepiness Scale (KSS); (b) EEG recordings (5 min eyes-open condition); and (c) PVT.ResultsSDEP induced a slowing of PVT reaction times (RTs), higher level of subjective sleepiness and an increase of delta, theta, alpha and beta 1 EEG activity. Only slowest PVT RTs were influenced by circadian factors, with longer RTs in the morning. Both fastest PVT RTs and KSS scores were positively correlated with post-SDEP changes in EEG theta activity, mainly in centro-posterior areas, but not with other EEG frequencies. KSS scores and PVT measures were also positively correlated.ConclusionsThese findings suggest that SDEP differently affects PVT variables, and that an increase in theta activity may be the principal EEG basis of the post-SDEP slowing of fastest PVT RTs. Similar neural mechanisms seem to underlie both performance deterioration to PVT and the increase of subjective sleepiness.     

Sleep homeostasis in the rat in the light and dark period

Sleep is regulated by the interaction of a homeostatic (Process S) and a circadian component. The duration of prior wakefulness is the main factor influencing subsequent sleep duration and its intensity. We investigated in the rat whether the sleep-wake history before sleep deprivation (SD) contributes to the effects of sleep loss incurred during the SD. A 24-h baseline recording was followed by 6 h SD at light onset (SD-Light, n=7), or at dark onset (SD-Dark, n=8) and 18 h recovery. Both SDs led to a pronounced increase in slow wave activity (SWA, EEG power between 0.75 and 4.0 Hz) in NREM sleep and increased sleep consolidation. The prolongation of sleep episodes was associated with increased intra-episode SWA. The amount of waking before the SD correlated positively with the SWA increase during recovery, and SWA levels before SD were negatively correlated with their subsequent increase. The time-course of SWA (Process S) as well as of single frequency bins within the SWA band was successfully simulated based on vigilance-state distribution. The time constant of the exponential monotonic decay (Td) was higher for the 0.75-1.0 Hz bin compared to all remaining frequency bins of the SWA band, reflecting a slower process determining the slow EEG component during sleep. The data show that the homeostatic response after SD, consisting of increased sleep intensity and sleep consolidation is determined by a combination of SD and the preceding vigilance-state history. The slower dynamics of low frequency delta power compared to fast delta frequencies point to heterogeneity within the traditionally defined SWA band.     

Effects of circadian phase and duration of sleep deprivation on sleep and EEG power spectra in the cat

The electroencephalogram (EEG) of cats was recorded under baseline conditions (LD 12:12) and after 4 and 8 h of sleep deprivation (SD). The EEG was analyzed by visual scoring and by spectral analysis. Under baseline conditions the 24-h distribution of sleep was bimodal: the smallest amounts of sleep occurred at the light-dark and dark-light transitions. EEG slow-wave activity (power density in the delta frequency range: 0.5-4.0 Hz) in non-rapid-eye-movement sleep (NREMS) showed a small variation over the 24-h period. When recovery sleep, following 4 h and 8 h of SD, started at the beginning of the dark period, no significant rebound of NREMS and REMS occurred during the 24-h recovery period. When recovery sleep, after 4 h of SD, started at the fifth hour of the light period, the amount of NREMS was increased. In all experiments the EEG power density in NREMS was enhanced after SD in the entire frequency range studied (0.5-31.5 Hz), but more prominently in the delta and theta (4.5-7.0 Hz) frequency bands. The effects dissipated in the course of the recovery period. The magnitude and duration of the enhancements of EEG power densities were dependent on the duration of SD and on the circadian phase at which SD was scheduled. It is concluded that in the cat sleep is a function of both circadian and homeostatic processes and that especially the EEG power density in NREMS is highly responsive to sleep loss.     

Circadian modulation of sequence learning under high and low sleep pressure conditions

Humans are able to learn complex sequences even without conscious awareness. We have studied the repercussions of circadian phase and sleep pressure on the ability to learn structured sequences using a serial reaction time task (SRT). Sixteen young healthy volunteers were studied in a 40-h "constant posture protocol" under high sleep pressure (i.e. sleep deprivation) and low sleep pressure conditions (i.e. sleep satiation attained by multiple naps). Here we show that learning of different sequence structures improved after multiple naps, in particular after naps that followed the circadian peak of rapid-eye-movement (REM) sleep. This situation following sleep contrasted with the lack of learning without sleep. We have evidenced that the observed amelioration of learning new sequences came about by memorizing short sub-fragments ("chunks") of the sequence train. However, SRT performance did not deteriorate under high sleep pressure, despite the high level of sleepiness. Our data indicate that sequence learning is modulated by circadian phase, and the neurophysiological medium required for this type of learning is related to sleep.     

Challenging the sleep homeostat: sleep in depression is not premature aging

ObjectivesThe close relationship between major depression and sleep disturbances led to the hypothesis of a deficiency in homeostatic sleep pressure in depression (S-deficiency hypothesis). Many observed changes of sleep characteristics in depression are also present in healthy aging, leading to the premise that sleep in depression resembles premature aging. In this study, we aimed at quantifying the homeostatic sleep–wake regulation in young women with major depression and healthy young and older controls under high sleep pressure conditions.MethodsAfter an 8-h baseline night nine depressed women, eight healthy young, and eight healthy older women underwent a 40-h sustained wakefulness protocol followed by a recovery night under constant routine conditions. Polysomnographic recordings were carried out continuously. Sleep parameters as well as the time course of EEG slow-wave activity (SWA) (EEG spectra range: 0.75–4.5 Hz), as a marker of homeostatic sleep pressure, were analyzed during the recovery night.ResultsYoung depressed women exhibited higher absolute mean SWA levels and a stronger response to sleep deprivation, particularly in frontal brain regions. In contrast, healthy older women exhibited not only attenuated SWA values compared to the other two groups, but also an absence of the frontal SWA predominance.ConclusionsHomeostatic sleep regulation and sleep architecture in young depressed women are not equal to premature aging. Moreover, our findings demonstrate that young moderately depressed women exhibit no deficiency in the sleep homeostatic process S as predicted by the S-deficiency hypothesis, but, rather, live on an elevated level of homeostatic sleep pressure.     

Dynamics of frontal EEG activity, sleepiness and body temperature under high and low sleep pressure.

The impact of sleep deprivation (high sleep pressure) vs sleep satiation (low sleep pressure) on waking EEG dynamics, subjective sleepiness and core body temperature (CBT) was investigated in 10 young volunteers in a 40 h controlled constant posture protocol. The differential sleep pressure induced frequency-specific changes in the waking EEG from 1-7 Hz and 21-25 Hz. Frontal low EEG activity (FLA, 1-7 Hz) during sleep deprivation exhibited a prominent increase as time awake progressed, which could be significantly attenuated by sleep satiation attained with intermittent naps. Subjective sleepiness exhibited a prominent circadian regulation during sleep satiation, with virtually no homeostatic modulation. These extremely different sleep pressure conditions were not reflected in significant changes of the CBT rhythm. The data demonstrate that changes in FLA during wakefulness are to a large extent determined by the sleep-wake dependent process with little circadian modulation, and reflect differential levels of sleep pressure in the awake subject.     

The circadian rhythm of atrial natriuretic peptide,vasoactive intestinal peptide,beta-endorphin and cortisol in healthy young and elderly subjects

Atrial natriuretic peptide, vasoactive intestinal peptide, beta-endorphin and cortisol are humoral variables characterized by a 24-h periodicity. We evaluated the circadian rhythm of these peptides and hormones in healthy subjects who were young (between 20–25 years) or elderly (between 65–75 years). All were on controlled diets. Blood samples were collected six times during a 24-h period (at 06.00, 08.00, 12.00, 18.00, 20.00 and 24.00 h) beginning 8-h after start of recumbency. The time-related data were analysed by the Cosinor method in order to validate the circadian rhythm and to quantify rhythmometric parameters which included the midline estimate of rhythm (mesor). In contrast to the young subjects, Cosinor analysis failed to reveal a significant circadian rhythm in elderly subjects, for plasma cortisol. In elderly subjects oscillation (mesor) of atrial nutriuretic peptide was higher, while that of vasoactive intestinal peptide and beta—endorphins was lower. The results suggest changes in the physiological secretion of these three peptides in healthy elderly subjects.     

The effect of gender on autonomic and respiratory responses during sleep among both young and middle-aged subjects

BACKGROUND AND OBJECTIVES: Sleep affects the control of circulation and respiratory function. Gender and age are also known to have a profound impact on the neural control of circulation. We investigated whether gender affects sleep-related cardiovascular and respiratory responses and whether these vary according to healthy subjects being young or middle-aged. METHODS: We studied 32 subjects: 8 women and 8 men aged 20-30 years (young), and 8 women and 8 men aged 50-60 years (middle-aged). Young women were under oral contraceptive therapy and middle-aged women were postmenopausal and not receiving hormonal replacement therapy. One-night polysomnography was used to assess RR variability during non-rapid eye movement (NREM) (stage 2) and rapid eye movement (REM) sleep. Low-frequency (LF) and high-frequency (HF) components, in normalized units (LFnu and HFnu) and LF/HF ratio were calculated on five-minute segments selected across the night and averaged for each sleep stage. The respiration frequency in NREM and REM sleep was also measured. Interaction between gender, age and sleep on autonomic and respiration variables was assessed by 2 x 2 x 2 analysis of variance (ANOVA). RESULTS: Compared to men, women had a greater NREM-to-REM increment in LFnu (gender-by-state interaction, p<0.01), a greater decrement in HFnu (interaction, p<0.01) and a greater increment in LF/HF (interaction, p<0.05). Women also showed a more pronounced increase in respiratory frequency during REM sleep compared to men in both groups of age (gender-by-state interaction, F=7.1, p<0.05). No gender-by-age-by-state interaction was observed to affect autonomic and respiration variables. CONCLUSION: NREM-to-REM excitatory cardiac and respiratory responses are more marked among women compared to men, regardless of their hormonal status and whether they are young or middle-aged.     

Sleep in normal aging]

Sleep in the elderly is characterized by a decrease in the ability to stay asleep resulting in a more fragmented sleep. Spindles are less frequent and less ample, shorter, without an increase during the night contrary young subjects. Delta activity in slow wave sleep is decreased in the 0.5-2 Hz frequency band only. REM sleep occurs earlier the first REM period duration increases. The REM sleep appearance is almost uniform during the night. REMs density does not increase toward the end of the sleeping period. The sleep-wake circadian rhythm is advanced (bedtime and morning awakening occur earlier). The temperature rhythm is also advanced. The rise in temperature after the nadir begins earlier for females and the initial ascent is more rapid. This explains why women wake up earlier and sleep for shorter durations than men. The nocturnal and diurnal mean plasmatic norepinephrine values increase. The rhythm of cortisol secretion is advanced. The GH and melatonin peaks of secretion are decreased. The acrophase of melatonin rhythm is occurring later in the elderly. These results suggest a weakening of circadian structure in the course of aging and an altered relationship between the pacemakers driving melatonin and cortisol circadian rhythms.     

Sleep effects of a 24-h versus a 16-h nicotine patch: a polysomnographic study during smoking cessation

BACKGROUND AND PURPOSE: Sleep disturbance is a common symptom of tobacco withdrawal and might contribute to early relapse vulnerability in abstinent smokers. This study was designed to compare the effects on sleep of nicotine patches applied either for 24 h (Nicopatch) or 16 h (Nicorette). PATIENTS AND METHODS: During a short smoking cessation period (48 h), this open-label, randomised, two-period crossover study compared the effects on sleep of the two nicotine patches in 20 heavy smokers (9 women, 11 men). During each period, polysomnographic recordings were performed from 12 pm to 7 am for two consecutive nights (baseline and treatment nights). Smoking cessation started from 8 pm the day of the baseline sleep recordings, and treatments were applied around 8 am the following morning. RESULTS: Compared to the 16-h nicotine patch, smokers who received the 24-h nicotine patch experienced significantly less microarousals, a greater proportion of slow wave sleep, a higher REM density and higher rapid eye movement (REM) beta activities. CONCLUSIONS: The results of this study suggest that a 24-h nicotine patch is more efficient than a 16-h nicotine patch to alleviate tobacco withdrawal-induced sleep disturbances.     

Daytime sleepiness associated with poor sustained attention in middle and late adulthood

ObjectiveWe aimed to determine the association between psychomotor vigilance task (PVT) performance and sleep-related factors including sleep duration, daytime sleepiness, poor sleep quality, insomnia, and habitual snoring in a population-based sample.MethodsThis was a cross-sectional analysis from the ongoing prospective cohort study, the Korean Genome and Epidemiology Study. We measured PVT performance and documented demographics, sleep-related factors, life style, and medical conditions in community dwelling adults (N = 2499; mean age 57.1 ± 7.3; male 1259). Associations between PVT parameters and sleep-related factors were tested, adjusting for age, gender, smoking, alcohol use, education, body mass index, hypertension, diabetes, depression, and the interval between mid-sleep time and PVT test.ResultsHigh Epworth Sleepiness Scale (ESS, ≥8) was associated with slower mean reciprocal response speed (mean RRT) (3.69 ± 0.02 vs. 3.77 ± 0.01, p < 0.001), higher probability for increased lapses (≥4) (OR 1.48, CI 1.12–1.88, p = 0.001), and more negative RRT slope (−0.036 ± 0.002 vs. −0.030 ± 0.001, p = 0.02). Older age, female gender, low education level, depressive mood, and the interval between mid-sleep and PVT test were also associated with poor performance. Sleep duration, habitual snoring, insomnia, or poor sleep quality (the Pittsburgh Sleep Quality Index score > 5) was not related to PVT parameters.ConclusionsAt the population level, our results revealed important modifiers of PVT performance, which included subjective reports of daytime sleepiness.     

TNFα G308A polymorphism is associated with resilience to sleep deprivation-induced psychomotor vigilance performance impairment in healthy young adults

Cytokines such as TNFα play an integral role in sleep/wake regulation and have recently been hypothesized to be involved in cognitive impairment due to sleep deprivation. We examined the effect of a guanine to adenine substitution at position 308 in the TNFα gene (TNFα G308A) on psychomotor vigilance performance impairment during total sleep deprivation. A total of 88 healthy women and men (ages 22–40) participated in one of five laboratory total sleep deprivation experiments. Performance on a psychomotor vigilance test (PVT) was measured every 2–3 h. The TNFα 308A allele, which is less common than the 308G allele, was associated with greater resilience to psychomotor vigilance performance impairment during total sleep deprivation (regardless of time of day), and also provided a small performance benefit at baseline. The effect of genotype on resilience persisted when controlling for between-subjects differences in age, gender, race/ethnicity, and baseline sleep duration. The TNFα G308A polymorphism predicted less than 10% of the overall between-subjects variance in performance impairment during sleep deprivation. Nonetheless, the differential effect of the polymorphism at the peak of performance impairment was more than 50% of median performance impairment at that time, which is sizeable compared to the effects of other genotypes reported in the literature. Our findings provided evidence for a role of TNFα in the effects of sleep deprivation on psychomotor vigilance performance. Furthermore, the TNFα G308A polymorphism may have predictive potential in a biomarker panel for the assessment of resilience to psychomotor vigilance performance impairment due to sleep deprivation.     

Effects of menstrual cycle phase and oral contraceptives on alertness, cognitive performance, and circadian rhythms during sleep deprivation.

The influence of menstrual cycle phase and oral contraceptive use on neurobehavioral function and circadian rhythms were studied in healthy young women (n = 25) using a modified constant routine procedure during 24 h of sleep deprivation. Alertness and performance worsened across sleep deprivation and also varied with circadian phase. Entrained circadian rhythms of melatonin and body temperature were evident in women regardless of menstrual phase or oral contraceptive use. No significant difference in melatonin levels, duration, or phase was observed between women in the luteal and follicular phases, whereas oral contraceptives appeared to increase melatonin levels. Temperature levels were higher in the luteal phase and in oral contraceptive users compared to women in the follicular phase. Alertness on the maintenance of wakefulness test and some tests of cognitive performance were poorest for women in the follicular phase especially near the circadian trough of body temperature. These observations suggest that hormonal changes associated with the menstrual cycle and the use of oral contraceptives contribute to changes in nighttime waking neurobehavioral function and temperature level whereas these factors do not appear to affect circadian phase.     

Melatonin treatment for circadian rhythm sleep disorders

Abstract We administered 1–3 mg melatonin to 11 patients (eight men, three women, aged 16–46 years) with circadian rhythm sleep disorders; nine with delayed sleep phase syndrome and two with non-24-hour sleep-wake syndrome. Sleep logs were recorded throughout the study periods and actigraph and rectal temperature were monitored during treatment periods. Melatonin was administered 1–2 h before the desirable bedtime for expected phase-shifting, or 0.5-1 h before habitual bedtime for gradual advance expecting an hypnotic effect of the melatonin. Melatonin treatments were successful in 6/11 patients. Timing and dose of melatonin administration, together with its pharmacological properties for circadian rhythm sleep disorders, should be further studied.     

Aging of core and optional sleep.

Two consecutive 24-hr ambulatory recordings of 14 healthy elderly persons (7 women, 7 men, ages 88-102) and of 19 healthy young adults (10 women, 9 men, ages 25-35) were evaluated. In addition to the classical sleep parameter analysis, sleep structure was also analyzed in terms of a proposed distinction between "core" and "optional" sleep (Horne 1989). Core sleep is the essential part of the sleep and is mainly slow wave sleep. This type of sleep is composed of stages 3 and 4 on non-REM sleep (NREM 3-4). Core sleep is obtained during the first three sleep cycles and the remainder of the night sleep is considered optional sleep. Optional sleep is more altered than core sleep. However, in both optional and core sleep, NREM sleep and REM are reduced. There is also an increase in drowsiness and in the time spent awake after sleep onset; however, the extent of these effects are more obvious in elderly men. Aging effects of slow wave sleep probably represent an amplification of the changes as observed in awake electroencephalic (EEG) patterns in healthy seniors. The decrease in slow wave sleep (stages NREM 3-4) is gender related and prevails in elderly men. REM sleep diminishes with increasing age. In the elderly, most REM sleep occurs at the beginning of the night. This contrasts to younger persons where the duration of REM sleep is longer at the end of the night. Furthermore, a decrease in REM sleep latency is particularly obvious in elderly men and probably secondary to the curtailment of slow wave sleep. The ultradian NREM-REM cycle rhythm (as defined by the periodic occurrence of REM sleep) shows a monophasic trend suggesting a diminished adaptive function of aged sleep. The informative value of true, continuous ambulatory recordings in the assessment of sleep-wakefulness patterns in normal and pathological aging is stressed.     

Associations of the 24-h activity rhythm and sleep with cognition: a population-based study of middle-aged and elderly persons

BackgroundCognitive functioning changes with age, sleep, and the circadian rhythm. We investigated whether these factors are independently associated with different cognitive domains assessed in middle-aged and elderly persons.MethodsIn 1723 middle-aged and elderly persons (age 62 ± 9.4 years, mean ± standard deviation, SD) of the Rotterdam Study, we collected actigraphy recordings of on average 138 h. Actigraphy was used to quantify 24-h rhythms by calculating the stability of the rhythm over days and the fragmentation of the rhythm. Sleep parameters including total sleep time, sleep-onset latency, and wake after sleep onset were also estimated from actigraphy. Cognitive functioning was assessed with the word learning test (WLT), word fluency test (WFT), letter digit substitution task (LDST), and Stroop color word test (Stroop).ResultsPersons with less stable 24-h rhythms performed worse on the LDST (B = 0.42 per SD increase, p = 0.004) and the Stroop interference trial (B = −1.04 per SD increase, p = 0.003) after full adjustment. Similarly, persons with more fragmented rhythms performed worse on the LDST (B = −0.47 per SD increase, p = 0.002) and the Stroop (B = 1.47 per SD increase, p <0.001). By contrast, longer observed sleep-onset latencies were related to worse performance on the WLT delayed recall (B = −0.19 per SD increase, p = 0.027) and the WFT (B = −0.45 per SD increase, p = 0.007).ConclusionsDisturbances of sleep and the 24-h activity rhythm were independently related to cognition; while persons with longer sleep-onset latencies had worse performance on memory and verbal tasks, persons with 24-h rhythm disturbances performed less on executive functioning and perceptual speed tasks.     

Sleep-stage-specific regulation of plasma catecholamine concentration

The catecholaminergic system is critically involved in the regulation of sleep, wake and arousal states. In the central nervous system, sleep is characterized by low levels of norepinephrine compared to wakefulness, reaching minimum levels during rapid eye movement (REM) sleep. It is not yet clear whether blood catecholamine concentrations (as a measure of sympathetic activity in the body periphery) show a similar sleep stage-dependent decline or depend mainly on a circadian rhythm. Here, we show that during sleep in humans, plasma concentrations of norepinephrine (NE) and epinephrine (E) exhibit a progressive decline associated with the stage of sleep, irrespective of the circadian time of sleep. In a within-subject design, healthy men (n=12) slept for 7h either during daytime or nighttime. Sleep was framed by 3-h periods of wakefulness during which subjects rested in a supine position. We sampled blood at a fast rate (1/10 min) and monitored blood pressure and heart rate continuously. Plasma catecholamine concentrations distinctly declined in a linear fashion as sleep deepened, reaching a minimum during REM sleep both during daytime and nighttime sleep. Diverging from this pattern, cardiovascular parameters indicated lowest blood pressure and heart rate during slow wave sleep (SWS), whereas during REM sleep activity increased almost to waking levels. Because the changes observed here in human blood catecholamine levels closely mimic the changes in brain catecholamine activity, as well-documented in animals, we suggest that the organism's overall catecholamine activity during sleep is well represented by measures of plasma catecholamine concentrations.     

Limbic thalamus and state-dependent behavior: The paraventricular nucleus of the thalamic midline as a node in circadian timing and sleep/wake-regulatory networks

The paraventricular thalamic nucleus (PVT), the main component of the dorsal thalamic midline, receives multiple inputs from the brain stem and hypothalamus, and targets the medial prefrontal cortex, nucleus accumbens and amygdala. PVT has been implicated in several functions, especially adaptation to chronic stress, addiction behaviors and reward, mood, emotion. We here focus on the wiring and neuronal properties linking PVT with circadian timing and sleep/wake regulation, and their behavioral implications. PVT is interconnected with the master circadian pacemaker, the hypothalamic suprachiasmatic nucleus, receives direct and indirect photic input, is densely innervated by orexinergic neurons which play a key role in arousal and state transitions. Endowed with prominent wake-related Fos expression which is suppressed by sleep, and with intrinsic neuronal properties showing a diurnal oscillation unique in the thalamus, PVT could represent a station of interaction of thalamic and hypothalamic sleep/wake-regulatory mechanisms. PVT could thus play a strategic task by funneling into limbic and limbic-related targets circadian timing and state-dependent behavior information, tailoring it for cognitive performance and motivated behaviors.     

Homeostatic sleep regulation is preserved in mPer1 and mPer2 mutant mice

A limited set of genes, Clock, Bmal1, mPer1, mPer2, mCry1 and mCry2, has been shown to be essential for the generation of circadian rhythms in mammals. It has been recently suggested that circadian genes might be involved in sleep regulation. We investigated the role of mPer1 and mPer2 genes in the homeostatic regulation of sleep by comparing sleep of mice lacking mPER1 (mPer1 mutants) or a functional mPER2 (mPer2 mutants), and wild-type controls (WT) after 6 h of sleep deprivation (SD). Our main result showed that after SD, all mice displayed the typical increase of slow-wave activity (SWA; EEG power density between 0.75 and 4 Hz) in nonREM sleep, reflecting the homeostatic response to SD. This increase was more prominent over the frontal cortex as compared to the occipital cortex. The genotypes did not differ in the effect of SD on the occipital EEG, while the effect on the frontal EEG was initially diminished in both mPer mutants. Differences between the genotypes were seen in the 24-h distribution of sleep, reflecting especially the phase advance of motor activity onset observed in mPer2 mutants. While the daily distribution of sleep was modulated by mPer1 and mPer2 genes, sleep homeostasis reflected by the SWA increase after 6-h SD was preserved in the mPer mutants. The results provide further evidence for the independence of the circadian and the homeostatic components underlying sleep regulation.