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.     

Baseline odor identification ability predicts degradation of psychomotor vigilance during 77 hours of sleep deprivation

Scores on the University of Pennsylvania Smell Identification Test, a measure of the functional integrity of the orbitofrontal cortex, were used to predict the vulnerability to cognitive declines during 77 hr of sleep deprivation. Twenty-one healthy volunteers completed the Smell Identification Test at rested baseline followed by repeated psychomotor vigilance testing throughout each night. Participants with better smell identification abilities sustained faster speeds and fewer lapses on the second and third nights of sleep deprivation than participants with lower scores. Individual differences in trait-like functioning of the orbitofrontal cortex are predictive of the ability to sustain alertness and vigilance during continuous wakefulness.     

Gender and age differences in psychomotor vigilance performance under differential sleep pressure conditions

The effects of sleep pressure and circadian phase on neurobehavioral function can be sensitively measured with the psychomotor vigilance task (PVT). We compared PVT performance in 16 young (8 men and 8 women, 20-31 years) and 16 elderly healthy subjects (8 men and 8 women, 57-74 years) during a 40-h sleep deprivation (SD, high sleep pressure) and a 40-h multiple nap protocol (NAP, low sleep pressure) under dim light and constant posture conditions in a balanced crossover design. Independent of age and sleep pressure conditions, women exhibited significantly slower reaction times (RTs) than men. This effect became more apparent with increasing time elapsed into both the 40-h NAP and SD protocol. However, women tended to have fewer premature key presses than men. Independent of gender, the elderly showed slower RTs than the young in the NAP protocol during the biological day (8-24 h) but not during the biological night (24-8 h). In the SD protocol, they had also significantly slower RTs but only during the first 16 h under low to moderate levels of sleep pressure conditions. The relative PVT performance decline after SD was significantly less pronounced in the elderly than in the young, so that both age groups exhibited similar performance decrements after 16 h into the SD protocol. Thus, nighttime- and sleep pressure-related RT slowing in the young "makes them old", or the elderly are less susceptible to circadian and wake-dependent PVT performance decrements. We interpret the gender effect as a different strategy in women when performing the PVT, although the instructions to be 'as fast as possible' were identical. Not only sleepiness and circadian phase, but also age and gender are major factors that may contribute to attentional failures in extended work shifts and during nighttime work shifts.     

Body posture affects electroencephalographic activity and psychomotor vigilance task performance in sleep-deprived subjects.

OBJECTIVE: This study examined the effects of posture on electroencephalographic (EEG) activity and psychomotor vigilance task (PVT) performance in 16 sleep-deprived volunteers. METHODS: EEG data were collected while participants completed 10 min PVTs under two counterbalanced sitting/standing conditions during 28 h of continuous wakefulness. RESULTS: In both the sitting and standing conditions, theta activity progressively increased as a function of sleep loss, but standing upright significantly attenuated this effect, suggesting that alertness was improved by the more upright posture. The PVT results showed that cognitive psychomotor performance was maintained at nearly well-rested levels by standing upright, whereas reaction time and attention noticeably deteriorated when participants were seated. CONCLUSIONS: These results suggest that an upright posture increases EEG arousal and sustained attention, indicating that postural manipulations can be useful for counteracting fatigue in sleep-deprived individuals.     

Compensatory recruitment after sleep deprivation and the relationship with performance

This study examined the effects of total sleep deprivation (TSD) on cerebral responses to a verbal learning task with two levels of word difficulty. A total of 32 subjects were studied with functional magnetic resonance imaging (FMRI) after normal sleep and following 36 h of TSD. Cerebral responses to EASY words were identical on both nights, but several brain regions showed increased activation to HARD words following TSD compared with following a normal night of sleep (NORM). These regions included bilateral inferior frontal gyrus, bilateral dorsolateral prefrontal cortex, and bilateral inferior parietal lobe. Better free recall performance on the HARD words after TSD was related to increased cerebral responses within the left inferior and superior parietal lobes and left inferior frontal gyrus. Recall was negatively related to activation within the right inferior frontal gyrus. Overall, the findings support the predictions of the compensatory recruitment hypothesis that task demands influence both the likelihood and location of increased cerebral activation during task performance following TSD, and refine that hypothesis by identifying a specific task demand that plays a role. The performance relationships suggest increased activation may be both beneficial (compensatory) and interfere with task performance, depending on the brain regions involved.     

Impaired neurobehavioral alertness quantified by the psychomotor vigilance task is associated with depression in the Wisconsin Sleep Cohort study

BackgroundExcessive daytime sleepiness plays an important role in the presentation and course of mood disorders. Standard objective measures of daytime sleep propensity are of little to no value in depressive illness. This study examined the psychomotor vigilance task (PVT), an objective measure of neurobehavioral alertness, and its cross-sectional and longitudinal associations with depressive symptomatology in the Wisconsin Sleep Cohort Study.MethodsThe sample consisted of 1569 separate 10-min PVT assessments conducted in 942 unique individuals. Cross-sectional and longitudinal conditional logistic regression models were used to estimate associations between the primary outcome of depression symptomatology (adjusted Zung scale≥50) and six separate PVT variables: mean reciprocal reaction time (1/RT); total lapses (RTs≥500 msec; LAPSE); total false responses (FALSE); reciprocal of the mean of the 10% fastest (FAST) and 10% slowest (SLOW) RTs; and slope of the linear regression line for all transformed 1/RTs (SLOPE).ResultsIn fully-adjusted cross-sectional models, 1/RT, LAPSE, FAST, and SLOW were each significantly associated with depression, such that worse neurobehavioral alertness was associated with higher odds of depressive symptomatology. Similar, though attenuated, findings were observed in fully-adjusted conditional longitudinal models that examined within-subject changes in depression status in the subset of participants with repeated PVT assessments. FALSE and SLOPE were not associated with depression in either cross-sectional or conditional longitudinal models.ConclusionsThese findings suggest components of the PVT are associated with depressive symptomatology. Further research is indicated to clarify the role of the PVT in the assessment of hypersomnolence in mood disorders.     

Meditation acutely improves psychomotor vigilance,and may decrease sleep need

Background  

A number of benefits from meditation have been claimed by those who practice various traditions, but few have been well tested in scientifically controlled studies. Among these claims are improved performance and decreased sleep need. Therefore, in these studies we assess whether meditation leads to an immediate performance improvement on a well validated psychomotor vigilance task (PVT), and second, whether longer bouts of meditation may alter sleep need.     

EEG and behavioural correlates of mild sleep deprivation and vigilance

ObjectiveThe current study investigated the behavioral, cognitive, and electrophysiological impact of mild (only a few hours) and acute (one night) sleep loss via simultaneously recorded behavioural and physiological measures of vigilance.MethodsParticipants (N = 23) came into the lab for two testing days where their brain activity and vigilance were recorded and assessed. The night before the testing session, participants either slept from 12am to 9am (Normally Rested), or from 1am to 6am (Sleep Restriction).ResultsVigilance was reduced and sleepiness was increased in the Sleep Restricted vs. Normally Rested condition, and this was exacerbated over the course of performing the vigilance task. As well, sleep restriction resulted in more intense alpha bursts. Lastly, EEG spectral power differed in Sleep Restricted vs. Normally Rested conditions as sleep onset progressed, particularly for frequencies reflecting arousal (e.g., delta, alpha, beta).ConclusionsThe findings of this study suggest that only one night of mild sleep loss significantly increases sleepiness and, importantly, reduces vigilance. In addition, this sleep loss has a clear impact on the physiology of the brain in ways that reflect reduced arousal.SignificanceUnderstanding the neural correlates and cognitive processes associated with loss of sleep may lead to important advancements in identifying and preventing deleterious or potentially dangerous, sleep-related lapses in vigilance.     

Sleep-related intermittent hypoxia is associated with decreased psychomotor vigilance in Japanese community residents

BackgroundSleep disordered breathing (SDB) is associated with decreased psychomotor vigilance (hereafter “vigilance”) in clinical settings, but this association has yet to be confirmed in the general population. The aim of this study is to determine the associations between SDB and vigilance in a large sample of community-based participants.MethodsThe study sample consisted of 1508 community-dwelling Japanese persons (age: 30–79 years, women: 62.7%, mean body mass index [BMI]: 23.1 kg/m²). Vigilance was measured by the psychomotor vigilance task (PVT), and SDB was measured by overnight pulse oximetry. We investigated odds ratios for “high mean reaction time (RT)” and “high number of lapses,” which we defined as the 75th percentile of each value, across categories of oximetry values (three percent oxygen desaturation index [ODI], 4% ODI, average oxygen saturation, minimum oxygen saturation).ResultsMultivariable-adjusted odds ratios of high mean RT and high number of lapses in severe SDB (3% ODI ≥ 30.0 events/h) were 3.0 (95% confidence interval: 1.0–8.9; P for trend = 0.03) and 3.3 (95% confidence interval: 1.2–9.2, P for trend = 0.03), respectively, compared to participants without SDB. Similar associations were observed between PVT metrics and four percent ODI. No significant associations between average oxygen saturation and PVT metrics were observed. Minimum oxygen saturation was significantly associated with the trend of high number of lapses (P for trend = 0.007), but not with high mean RT.ConclusionsThe present study provides evidence that the intermittent hypoxia in SDB is significantly associated with the deterioration of PVT outcome metrics.     

The relationships between improvements in daytime sleepiness,fatigue and depression and psychomotor vigilance task testing with CPAP use in patients with obstructive sleep apnea

ObjectiveThe purpose of this study was to determine if the subjective improvements in daytime sleepiness, fatigue and depression experienced by patients with obstructive sleep apnea (OSA) with continuous positive airway pressure (CPAP) therapy predict an objective improvement in vigilance, and whether patients with mild-to-moderate OSA differ from patients with severe OSA in this regard.MethodsA total of 182 patients underwent psychomotor vigilance task (PVT) testing and measurements of subjective daytime sleepiness, fatigue and depression at baseline and after a minimum of one month of adherent CPAP use at an adequate pressure.ResultsPatients with both mild-to-moderate (n = 92) and severe (n = 90) OSA experienced improvements in subjective daytime sleepiness, fatigue and depression, but objective improvement in vigilance was only seen in patients with severe OSA. In patients with severe OSA, while a correlation was found between improvements in daytime sleepiness and some PVT parameters, changes in subjective daytime sleepiness, fatigue and depression scores were not predictive of objective improvement in vigilance while controlling for all these subjective symptoms and for age, gender, body mass index, apnea-hypopnea index/respiratory event index and total sleep time/total recording time with pulse oximetry below 90%.ConclusionsWe found no predictive relationship between subjective improvements in daytime sleepiness, fatigue and depression and objective vigilance with CPAP use in patients with OSA. These results suggest that subjective complaints of daytime impairment and objective measures of vigilance in patients with OSA should be assessed separately while evaluating the efficacy of CPAP therapy on daytime functioning.     

fMRI activation during failures to respond key to understanding performance changes with sleep deprivation

The reticulon-4 receptor, encoded by RTN4R, limits axonal sprouting and neural plasticity by inhibiting the outgrowth of neurites. Human association studies have implicated mutations in RTN4R in the development of schizophrenia, including the identification of several rare nonconservative missense mutations of RTN4R in schizophrenia patients. To investigate the effects of missense mutation of the reticulon-4 receptor on phenotypes relevant to schizophrenia, we behaviourally characterized a novel Rtn4r mutant mouse line with an amino acid substitution (R189H) in the Nogo-66 binding site. Behavioural assays included prepulse inhibition of acoustic startle, locomotor activity, social interaction and spatial cognition. When compared with wildtype littermates, Rtn4r mutant mice exhibited greater social preference, which may reflect a social-anxyolitic effect, and a mild impairment in spatial cognition. Given the mild effect of the R189H mutation of Rtn4r on behavioural phenotypes relevant to schizophrenia, our results do not support missense mutation of RTN4R as a strong risk factor in the pathogenesis of schizophrenia.     

Human sleep spindle characteristics after sleep deprivation

OBJECTIVE: Sleep spindles (12-15 Hz oscillations) are one of the hallmarks of the electroencephalogram (EEG) during human non-rapid eye movement (non-REM) sleep. The effect of a 40 h sleep deprivation (SD) on spindle characteristics along the antero-posterior axis was investigated. METHODS: EEGs during non-REM sleep in healthy young volunteers were analyzed with a new method for instantaneous spectral analysis, based on the fast time frequency transform (FTFT), which yields high-resolution spindle parameters in the combined time and frequency domain. RESULTS: FTFT revealed that after SD, mean spindle amplitude was enhanced, while spindle density was reduced. The reduction in spindle density was most prominent in the frontal derivation (Fz), while spindle amplitude was increased in all derivations except in Fz. Mean spindle frequency and its variability within a spindle were reduced after SD. When analyzed per 0.25 Hz frequency bin, amplitude was increased in the lower spindle frequency range (12-13.75 Hz), whereas density was reduced in the high spindle frequency range (13.5-14.75 Hz). CONCLUSIONS: The observed reduction in spindle density after SD confirms the inverse homeostatic relationship between sleep spindles and slow waves whereas the increase in spindle amplitude and the reduction in intra-spindle frequency variability support the hypothesis of a higher level of synchronization in thalamocortical cells when homeostatic sleep pressure is enhanced.     

Cardiac autonomic changes after 40 hours of total sleep deprivation in women

ObjectivesThe effect of total sleep deprivation on heart rate variability (HRV) in groups of postmenopausal women on oral hormone therapy (HT) (on-HT, n = 10, 64.2 (1.4) years), postmenopausal women without HT (off-HT, n = 10, 64.6 (1.4) years) and young women (n = 11, 23.1 (0.5) years) was studied using a prospective case–control setup.MethodsPolysomnography was performed over an adaptation night, a baseline night, and a recovery night after 40 h of total sleep deprivation. Time and frequency domain and nonlinear HRV from overnight electrocardiogram recordings were compared between groups during baseline and recovery nights. Further, the changes in HRV from baseline to recovery were analysed and compared between groups. Finally, correlations of HRV to percentages of sleep stages and measures of sleep fragmentation were analysed during baseline and recovery.ResultsYoung women had higher HRV than older women; the most marked difference was between young and on-HT postmenopausal women. Sleep deprivation induced a decrease in frequency domain HRV in young and in off-HT women, an increase in α2 in off-HT women, and an increase in mean heart rate in on-HT women. The sleep deprivation effect was mainly uncorrelated to changes in sleep parameters.ConclusionsAcute total sleep deprivation has a deleterious effect on the autonomic nervous system in young women, but an even more pronounced effect in postmenopausal women. Hormone therapy use in late postmenopause does not give protection against these changes. These harmful effects may partly explain the increased cardiovascular morbidity and overall mortality associated with sleep loss.     

An event-related fMRI study of the neurobehavioral impact of sleep deprivation on performance of a delayed-match-to-sample task

Eighteen subjects (ages 18-35) underwent event-related functional magnetic resonance imaging (efMRI) while performing a delayed-match-to-sample (DMS) task before and immediately after 48 h of sustained wakefulness. The DMS trial events were: a 3-s study period of either a one-, three-, or six-letter visual array; a 7-s retention interval; and a 3-s probe period, where a button press indicated whether the probe letter was in the study array. Ordinal Trend Canonical Variates Analysis (OrT CVA) was applied to the data from the probe period for trials with six-letter study lists prior to and immediately following sleep deprivation to find an activation pattern whose expression decreased with sleep deprivation in as many subjects as possible, while being present in both conditions. The first principal component of the OrT analysis identified a covariance pattern whose expression decreased as a function of sleep deprivation in 17 of 18 subjects (p<0.001). While overall expression of the pattern showed a systematic decrease with sleep deprivation, the brain regions that make up the pattern show covarying increases and decreases in activation. Regions that decreased their activation were noted in the parietal (BA 7 and 40), temporal (BA 37, 38 and 39) and occipital (BA 18 and 19) lobes; regions that increased their activation were noted in the cerebellum, basal ganglia, thalamus and the anterior cingulate gyrus (BA 32). The reduction in pattern expression with sleep deprivation for each subject was related to the change in performance on the DMS task. Subject decreases in pattern expression were correlated with reductions in recognition accuracy (p<0.05), increased intra-individual variability in reaction time (p<0.005) and increased lapsing (p<0.005).     

Poor recovery sleep after sleep deprivation in delayed sleep phase syndrome

To clarify disturbances in sleep regulation in patients with delayed sleep phase syndrome (DSPS), we studied three patients with DSPS and seven healthy controls. Sleep propensity and melatonin rhythms after 24-h sleep deprivation were investigated under dim light condition by using the ultra-short sleep-wake schedule. The sleep propensity curves displayed clear differences between DSPS patients and the controls. During the subjective day when melatonin was not produced, recovery sleep after the sleep deprivation did not occur in DSPS patients, while recovery sleep occurred during the subjective day in controls. This suggests that DSPS may involve problems related to the homeostatic regulation of sleep after sleep deprivation.