Time as a Measure of Consciousness. Subjective Time in Waking and Different Sleep Phases

Neuroscience and Behavioral Physiology - This review presents results from studies addressing the problem of the experience of time in waking and sleep. The adaptive value of the sensation of time...     

Sustaining Executive Functions During Sleep Deprivation: A Comparison of Caffeine,Dextroamphetamine, and Modafinil

Objectives:

Stimulant medications appear effective at restoring simple alertness and psychomotor vigilance in sleep deprived individuals, but it is not clear whether these medications are effective at restoring higher order complex cognitive capacities such as planning, sequencing, and decision making.

Design:

After 44 hours awake, participants received a double-blind dose of one of 3 stimulant medications or placebo. After 45–50 hours awake, participants were tested on computerized versions of the 5-Ring Tower of Hanoi (TOH), the Tower of London (TOL), and the Wisconsin Card Sorting Test (WCST).

Setting:

In-residence sleep-laboratory facility at the Walter Reed Army Institute of Research.

Participants:

Fifty-four healthy adults (29 men, 25 women), ranging in age from 18 to 36 years.

Interventions:

Participants were randomly assigned to 1 of 3 stimulant medication groups, including caffeine, 600 mg (n = 12), modafinil, 400 mg (n = 12), dextroamphetamine, 20 mg (n = 16), or placebo (n = 14).

Measurements and Results:

At the doses tested, modafinil and dextroamphetamine groups completed the TOL task in significantly fewer moves than the placebo group, and the modafinil group demonstrated greater deliberation before making moves. In contrast, subjects receiving caffeine completed the TOH in fewer moves than all 3 of the other groups, although speed of completion was not influenced by the stimulants. Finally, the modafinil group outperformed all other groups on indices of perseverative responding and perseverative errors from the WCST.

Conclusions:

Although comparisons across tasks cannot be made due to the different times of administration, within-task comparisons suggest that, at the doses tested here, each stimulant may produce differential advantages depending on the cognitive demands of the task.

Citation:

Killgore WDS; Kahn-Greene ET; Grugle NL; Killgore DB; Balkin TJ. Sustaining Executive Functions During Sleep Deprivation: A Comparison of Caffeine, Dextroamphetamine, and Modafinil. SLEEP 2009;32(2):205–216.     

Discrepancies Between Self-Reported Usual Sleep Duration and Objective Measures of Total Sleep Time in Treatment-Seeking Overweight and Obese Individuals

To examine the agreement between actigraphy-estimated and self-reported sleep duration in obese individuals, we had 63 treatment seeking overweight/obese participants complete the Pittsburgh Sleep Quality Index (PSQI) and report sleep duration for weekends and weekdays, and compared their reports to 7 days of actigraphy. Actigraph total sleep time correlated r = .20-.31 with self-report and the absolute discrepancy averaged 51-54 minutes. Only 20 of the 32 subjects (62.5%) classified as short sleepers (<7 hours/night) by actigraphy were similarly classified by self-report. Poor sleep quality was associated with greater absolute discrepancy between actigraphy and self-report. The weak correlations between self-report and actigraph should be considered in future efforts to increase sleep duration to promote weight loss in obese individuals.     

Long Sleepers Sleep More and Short Sleepers Sleep Less: A Comparison of Older Adults Who Sleep Well

To determine some of the risks and benefits of being a long or short sleeper, psychological adjustment, lifestyle, and sleep parameters were investigated in 239 older adults. Responses of people who slept well and who were either long or short sleepers were studied on 48 variables investigating sleep parameters and sleep-related affect and beliefs; daytime fatigue and sleepiness; demographic factors, including age, sex, and income satisfaction; sleep lifestyle factors, including naps, bedtimes, arising times, and the regularity of these; general lifestyle factors, including regularity of mealtimes, overall daytime pleasantness, perceived busyness, diversity and valence of daily activities, and potentially stressful major life events. In addition, 14 variables evaluated aspects of psychological adjustment, including cognitive and somatic arousal, nocturnal tension, anxious, negative, unpleasant and worrying self-talk, depression, anxiety, overall psychopathology, neuroticism, and life satisfaction. Overall, the results indicate that short sleepers get up earlier, spend less time in bed, and have lower sleep efficiencies than their long sleeper counterparts. They eat breakfast earlier, and of course, they sleep less. Only one of the 14 psychological adjustment variables was significant. In view of the many differences between short and long sleepers described in prior research, the lack of differences observed between long and short sleepers is noteworthy.     

不同海拔健康青年男性心率变异性对比分析

应用短程心率变异性（HRV）时域、频域和非线性分析法，对比进入三个不同海拔高度自主神经系统（ANS）调节功能的特点。发现：与进入海拔1856m相比．海拔2800m平均正常RR间期的标准差（SDNN）、相邻RR间期差的均方根（rMSSD）、相差〉50ms的相邻RR间期占RR间期总数的百分比（PNNS0）、低频成分（LF）、高频成分（HF）以及总功率（TP）均有轻度升高，但无统计学差异；与进入海拔1856m和海拔2800m相比．海拔3040mSDNN、rMSSD、LF和HF显著降低。这表明进入海拔3040m副交感神经活动显著减弱、自主神经系统调节功能显著受抑。自主神经的这种变化有助于进一步阐明进入高海拔机体发生的病理生理学改变。     

Sleep and the Transition to Adolescence: A Longitudinal Study

Study Objectives:

To assess the links between sleep and pubertal development using a longitudinal design.

Design:

Three consecutive annual assessments of sleep and pubertal development. Sleep was assessed using a week of home actigraphy.

Setting:

Naturalistic sleep in the home setting of school children, Tel Aviv Area, Israel.

Participants:

A sample of 94 (41 boys) typically developing healthy school-age children (age range at first assessment: 9.9–11.2 years).

Intervention:

N/A

Measurements and Results:

The Petersen''s Pubertal Development Scale (PDS) and Sexual Maturation Scale (SMS) were used to assess pubertal development, and a week of actigraphy served to assess naturalistic sleep patterns. The results reflect expected developmental trends: an increase in signs of pubertal maturation, delayed sleep onset, and shorter sleep time. After controlling for age, significant relationships were found between sleep onset time, true sleep time, and number of night wakings at Time 1 and pubertal ratings at Time 2, and pubertal changes from Time 1 to Time 2. Delayed and disrupted sleep at Time 1 predicted faster pubertal changes from Time 1 to Time 2. These results were supported by structural equation modeling. These findings were similar in boys and girls.

Conclusions:

Based on these longitudinal data, it appears that pubertal changes in sleep (delayed sleep phase and disrupted sleep patterns) antedate bodily changes associated with puberty. The underlying mechanisms explaining these predictive links should be further explored.

Citation:

Sadeh A; Dahl RE; Shahar G; Rosenblat-Stein S. Sleep and the transition to adolescence: a longitudinal study. SLEEP 2009;32(12):1602-1609.     

Standardize and Compare Contrast-enhanced Ultrasonographic Digital Images Obtained with Different Technologies: How to Overcome the Subjectivity

Objective This study was conducted to compare digital images obtained with cadence contrast pulse sequencing (CPS) and coherent contrast imaging (CCI) technologies for contrast-enhanced ultrasonography (CEUS). Methods A CEUS study on 17 focal liver lesions was performed using CPS and CCI technologies with a second-generation contrast media. The lesion/liver ratio and conspicuity index were then calculated and compared with Adobe Photoshop 6.0. Results Lesion/liver ratio and conspicuity index using CCI ranged from 1.3 to 7.1 (mean value, 3) and 19 to 127 (mean value, 58), respectively; by using CPS, we obtained results ranging from 2 to 19.1 (mean value, 8.9) and 57 to 164 (mean value, 109.2). Lesion/liver ratio and the conspicuity index for the lesions using CPS showed significantly (p < 0.0001) superior results than those obtained using CCI. Conclusion The computed analysis with standardization allows an objective evaluation of digital images of CEUS. CPS technology resulted in better lesion conspicuity compared to CCI during CEUS study on focal liver lesions.     

Idiopathic Hypersomnia with and without Long Sleep Time: A Controlled Series of 75 Patients

Objective:

To characterize the clinical, psychological, and sleep pattern of idiopathic hypersomnia with and without long sleep time, and provide normative values for 24-hour polysomnography.

Setting:

University Hospital

Design:

Controlled, prospective cohort

Participants:

75 consecutive patients (aged 34 ± 12 y) with idiopathic hypersomnia and 30 healthy matched controls.

Intervention:

Patients and controls underwent during 48 hours a face-to face interview, questionnaires, human leukocyte antigen genotype, a night polysomnography and multiple sleep latency test (MSLT), followed by 24-h ad libitum sleep monitoring.

Results:

Hypersomniacs had more fatigue, higher anxiety and depression scores, and more frequent hypnagogic hallucinations (24%), sleep paralysis (28%), sleep drunkenness (36%), and unrefreshing naps (46%) than controls. They were more frequently evening types. DQB1*0602 genotype was similarly found in hypersomniacs (24.2%) and controls (19.2%). Hypersomniacs had more frequent slow wave sleep after 06:00 than controls. During 24-h polysomnography, the 95% confidence interval for total sleep time was 493–558 min in controls, versus 672–718 min in hypersomniacs. There were 40 hypersomniacs with and 35 hypersomniacs without long ( > 600 min) sleep time. The hypersomniacs with long sleep time were younger (29 ± 10 vs 40 ± 13 y, P = 0.0002), slimmer (body mass index: 26 ± 5 vs 23 ± 4 kg/m²; P = 0.005), and had lower Horne-Ostberg scores and higher sleep efficiencies than those without long sleep time. MSLT latencies were normal ( > 8 min) in 71% hypersomniacs with long sleep time.

Conclusions:

Hypersomnia, especially with long sleep time, is frequently associated with evening chronotype and young age. It is inadequately diagnosed using MSLT.

Citation:

Vernet C; Arnulf I. Idiopathic Hypersomnia with and without Long Sleep Time: A Controlled Series of 75 Patients. SLEEP 2009;32(6):753-759.     

Auditory Evoked Potential in Stage 2 and REM Sleep During a 30-Day Exposure to Tone Pulses

Ten subjects were exposed to 3.5K Hz tone pulses of 660 msec duration, presented 24-hr-per-day for 30 days. The interstimulus interval was 22 sec. There were 10 days each at 80, 85, and 90 dB in that order. The average evoked potential (AEP) at C₃ referenced to linked mastoids was obtained from contiguous stage 2 and REM sleep segments on the first, second, and last recorded nights of tone-pulse exposure. The AEP was consistently larger in stage 2 than in REM sleep. In both stage 2 and REM sleep, AEP amplitude on the second recorded night bore no consistent relationship to first or last recorded night AEPs. Only the N2–P3 amplitude yielded consistent decreases, with 9 of 10 subjects in both stage 2 and REM sleep having smaller N2–P3 amplitudes on the last than on the first recorded night. There were no changes in latency of any component. During sleep there is little, if any, habituation of the auditory AEP during long-duration exposures to nonmeaningful stimuli, and certainly no extinction of the AEP under these conditions.     

Evidence of Subthalamic PGO-like Waves During REM Sleep in Humans: A Deep Brain Polysomnographic Study

Study Objectives:

The aim of this study was to examine whether the subthalamic nucleus (STN) plays a role in the transmission of PGO-like waves during REM sleep in humans.

Design:

Simultaneous recordings from deep brain electrodes to record local field potentials (LFPs), and standard polysomnography to ascertain sleep/wake states.

Setting:

Main Hospital, department of clinical neurophysiology sleep laboratory.

Participants:

12 individuals with Parkinson''s disease, with electrodes implanted in the STN; and, as a control for localization purposes, 4 cluster headache patients with electrodes implanted in the posterior hypothalamus.

Interventions:

All subjects underwent functional neurosurgery for implantation of deep brain stimulation electrodes.

Results:

Sharp, polarity-reversed LFPs were recorded within the STN during REM sleep in humans. These subthalamic PGO-like waves (2–3 Hz, 80–200 μV, and 300–500 msec) appeared during REM epochs as singlets or in clusters of 3–13 waves. During the pre-REM period, subthalamic PGO-like waves were temporally related to drops in the submental electromyogram and/or onset of muscular atonia. Clusters of PGO-like waves occurred typically before and during the bursts of rapid eye movements and were associated with an enhancement in fast (15–35 Hz) subthalamic oscillatory activity.

Conclusion:

Subthalamic PGO-like waves can be recorded during pre-REM and REM sleep in humans. Our data suggest that the STN may play an active role in an ascending activating network implicated in the transmission of PGO waves during REM sleep in humans.

Citation:

Fernández-Mendoza J; Lozano B; Seijo F; Santamarta-Liébana E; Ramos-Platón MJ; Vela-Bueno A; Fernández-González F. Evidence of subthalamic PGO-like waves during REM sleep in humans: a deep brain polysomnographic study. SLEEP 2009;32(9):1117-1126.     

A Comparison of the Telediagnostic and Medilog Systems for Recording Normal Sleep in the Home Environment

Two home recording systems, the Telediagnostic (TDS) and the Medilog, were used to compare sleep in the home environment with recorded sleep from the laboratory environment in 24 normal subjects (ages 21–42). Each subject was recorded for 4 consecutive nights, 2 each in the home and laboratory environments, in a counterbalanced order. All recorded sleep was manually scored for sleep latency, sleep efficiency, sleep maintenance, sleep stage architecture, REM sleep latency, and REM sleep activity. Complete data on 10 subjects using the TDS (Experiment 1) and 10 subjects using the Medilog System (Experiment 2) were available for statistical analyses. There were no significant differences in any of the nine sleep parameters tested by recording environment or order of recording environments using the Telediagnostic or the Medilog systems. Comparing the sleep parameters recorded across experiments, subjects recorded with the TDS took longer to fall asleep in the home environment than those subjects recorded with the Medilog System. The TDS demonstrated a clear superiority over the Medilog System in its sleep monitoring feasibility and its practical and economic advantages for carrying out home sleep studies.     

Rapid Time to Results and High Sensitivity of the CarbaNP Test on Early Cultures

For rapid results, we adapted the CarbaNP test by using 5-hour-old cultures; the sensitivity and specificity for detection of carbapenemase production were 100% for non-OXA-producing organisms. The sensitivity from early cultures was 94% for detection of carbapenemase production in Enterobacteriaceae strains. Utilizing younger cultures allows the test to be incorporated into a single day''s workflow, facilitating timely patient care and antimicrobial stewardship.     

Sensitivity to Change Following Liver Transplantation: A Comparison of Three Instruments that Measure Quality of Life

There is an increasing focus on the importance of quality-of-life (QOL) factors in evaluating the efficacy of medical and surgical interventions. There are a wide number of instruments currently available, and the aim of the present study was to evaluate the relative sensitivity to change of three widely used QOL measures, the WHOQOL-100, the SF-36 and the Rotterdam Symptom Checklist, focusing on psychological and physical components of life quality. Fifty patients were assessed pre- and 3 months post-liver transplantation. In addition, 21 patients with liver disease but who were not transplanted were assessed twice, separated by a 3-month interval, in order to serve as a comparison group. All QOL measures showed significant improvement following liver transplantation, whereas the control group showed no significant within-subject change on any measure. We employed the Standardised Response Mean (SRM) effect size as our index of clinically meaningful change in QOL measures. Large SRM effect sizes were obtained following liver transplantation for WHOQOL-100 and SF-36 summary measures, and for the Rotterdam physical subscale. In contrast, the traditional SF-36 scale scores and Rotterdam psychological subscale exhibited only moderate sensitivity to change.     

EEG Characteristics and Anxiety Levels in Subjects with Different Levels of Success in Recovering Psychomotor Activity on Waking During Daytime Sleep

Neuroscience and Behavioral Physiology - Studies in healthy adult volunteers with different levels of anxiety addressed the effectiveness of recovery of monotonous activity after brief episodes of...     

Sleep deprivation in the rat: XIV. Comparison of waking hypothalamic and peritoneal temperatures

Earlier studies of rats subjected to total sleep deprivation (TSD) by the disk-over-water method had shown an initial increase in waking peritoneal temperature (T(ip)) followed by an even greater decrease as deprivation proceeded. In the present study, hypothalamic temperature (T(hy)), as well as T(ip), were recorded continuously. As in the earlier studies, TSD rats showed an increase in energy expenditure and an initial increase followed by a decrease in T(ip). Waking T(hy) showed a more prolonged initial rise and a smaller late decline than waking T(ip) Assuming that, as the literature suggests, T(hy) is held closer to temperature setpoint (TSET) than is T(ip), the present results suggest an elevated waking TSET during deprivation. T(ip) became progressively lower than T(hy) over the course of deprivation, indicating a decreased ability to maintain the whole body near TSET. This decreased ability could result from insufficient thermogenesis or excessive heat loss. Because thermogenesis rose progressively throughout deprivation, heat loss must have increased even more than heat production. Thus, the results are consistent with other data which indicate that TSD in the rat produces two opposing effects on waking temperature, an elevation of setpoint and excessive heat loss, which together increase the demand for energy expenditure.