States of rest and activity in the Commerson's dolphin <Emphasis Type="Italic">Cephalorhynchus commersonii</Emphasis>

The unihemispheric slow-wave sleep, the ability to sleep during swimming with one open eye and the absence of paradoxical sleep in its form observed in all terrestrial mammals are unique features of sleep in cetaceans. Visual observation supplement electrophysiological studies and allow obtaining novel data about sleep of cetaceans. In the present study we examined behavior of 3 adult Commerson's dolphins Cephalorhynchus commersonii kept in the oceanarium Sea World (San Diego, CA, USA). The behavior of the dolphins can be subdivided into 5 swimming types: (1) active swimming marked by variable and irregular trajectory of movement (for 3 dolphins, on average, 35.1 ± 2.7% of the 24-h period) was the active wakefulness; (2) circular swimming was divided into the slow and fast swimming and occupied, on average, 44.4 ± 3.8 and 9.7 ± 0.8% of the 24-h period, respectively; during the circular swimming, dolphins performed from 1 to 6 circular swimming during one respiration pause; (3) quiet chaotic swimming (3.9 ± 1.2%) that occurred at the bottom and was not accompanied by signs of activity; (4) hanging, and (5) slow swimming at the surface (4.1 ± 0.5 and 2.8 ± 0.4%) respectively; the latter two swimming types were accompanied by frequent respiration (hyperventilation). We suggest that the sleep state in Commerson's dolphins occurs predominantly during the circular and quiet swimming. From time to time the dolphins decreased the speed, up to complete stop. Such episodes appeared to be the deepest sleep episodes. In all dolphins, muscle jerks as well erection in male are observed. Most jerks and erections occurred during the circular and quiet chaotic swimming. Thus, Commerson's dolphins, like other studied small cetaceans, are swimming for 24 h per day and they sleep during the swimming. Some muscle jerks that were observed in the dolphins in this study might have been brief episodes of paradoxical sleep.     

Asynchronous Eye Closure as an Anti-Predator Behavior in the Western Fence Lizard (Sceloporus occidentalis)

Asynchronous eye closure (ASEC), one eye open while the other is closed, is a behavior observed in birds, some aquatic mammals, and reptiles. In birds and aquatic mammals, ASEC is associated with unihemispheric sleep wherein the cerebral hemisphere contralateral to (i.e. neurologically connected to) the closed eye sleeps while the other cerebral hemisphere remains awake with its associated eye open and functional. Evidence from birds suggests that ASEC is an important anti‐predator adaptation to mediate the trade‐off between the need to remain vigilant and the need to sleep. However, the anti‐predator correlates of ASEC remain largely unstudied in other animals. Here, we present behavioral evidence that ASEC in reptiles is also an anti‐predator adaptation used in response to an increase in the risk of predation. ASEC was measured in captive western fence lizards (Sceloporus occidentalis) individually exposed to three experimental treatments: (1) an empty terrarium, (2) a terrarium housing a novel moving object, and (3) a terrarium housing a live predator (snake). Predator exposure elicited significantly higher levels of vigilance, mostly due to an increase in ASEC. This increase in ASEC came largely at the expense of synchronous eye closure (both eyes closed). Lizards in ASEC also showed a strong tendency to orient their open eye in the direction of the predator. We suggest that lizards engaged in ASEC are sleeping unihemispherically and are thus able to maintain a level of vigilance concurrent with sleep.     

NONLINEAR BEHAVIOR OF HUMAN RESPIRATORY MOVEMENT DURING DIFFERENT SLEEP STAGES

To investigate the nonlinear properties of respiratory movement during different sleep stages, we applied an algorithm proposed by Grassberger and Procaccia to calculate the correlation dimension in rapid eye movement and non-rapid eye movement sleep. We also tested for nonlinearity in respiratory movement by comparing the correlation dimension for the original data with that for surrogate data. The study population included eight healthy volunteers. We recorded respiratory movement and the sleep electroencephalogram for 8 h. The correlation dimension for respiratory movement was 3.28 ± 0.19 (mean ± SD) during rapid eye movement sleep, 2.31 ± 0.21 during light sleep (stage I) and 1.64 ± 0.25 during deep slow-wave sleep (stage IV). Thus, the correlation dimension differed significantly by sleep stage (p < 0.001): it was least during stage IV sleep and greatest during REM. The correlation dimension for the original data also differed from that for surrogate data, confirming nonlinearity in original data. The results suggest that the nonlinear dynamics of respiratory movement in sleep changes with sleep stage, presumably due to the information processing by the cerebral cortex. The increased correlation dimension for respiratory movement in REM sleep may be related to increased cortical information processing associated with dreaming. (Chronobiology International, 18(1), 71–83, 2001)     

Bullying,sleep/wake patterns and subjective sleep disorders: Findings from a cross-sectional survey

The aim of this study was to explore: (a) sleep patterns and disorders possibly associated with adolescent bullying profiles (pure bully, pure victim, bully/victim and neutral) and (b) the effect of sleep on psychosocial problems (externalized and internalized) related to bullying. The sample consisted of 1422 students aged 10–18 (mean?=?14.3, SD?=?2.7; 57% male) from five socioeconomically diverse schools in France. Bullying profiles were obtained using the revised Bully–Victim Questionnaire. Subjective sleep disorders were assessed using the Athens Insomnia Scale. School-week and weekend sleep/wake patterns were recorded. Internalizing problems were investigated using a Perceived Social Disintegration Scale and a Psychological Distress Scale. Externalizing behaviors were assessed using a General Aggressiveness Scale and an Antisocial Behavior Scale. These questionnaires were administered during individual interviews at school. After controlling for effects of gender and age, victims of bullying showed significantly more subjective sleep disturbances than the pure-bully or neutral groups (p?<?0.001). Bullies’ sleep schedules were more irregular (p?<?0.001 for bedtime irregularity and p<0.01 for wake-up time irregularity) and their sleep duration was shorter than their schoolmates (p?<?0.001 for the school week and p?<?0.05 for the weekend). There was an effect of sleep on psychosocial problems related to bullying, and our results indicate that sleep has a moderating effect on aggression in bullies (p?<?0.001). This would suggest a higher vulnerability of bullies to sleep deprivation. These results show differences in sleep problems and patterns in school-bullying profiles. Findings of this study open up new perspectives for understanding and preventing bullying in schools, with implications for research and clinical applications.     

Why do birds sleep with one eye open? Light exposure of the chick embryo as a determinant of monocular sleep.

Together with some aquatic mammals, birds exhibit a unique behavioral and electrophysiological state called "unihemispheric sleep," in which one cerebral hemisphere is awake and the other is sleeping. Slow-wave sleep in one hemisphere is associated with closure of the contralateral eye, while the eye contralateral to the awake hemisphere is open; closure of both eyes, in contrast, is associated with bihemispheric slow-wave sleep or with REM sleep. During the last few days of incubation, the chick's embryo is turned in the egg so that it occludes its left eye, whereas light entering through the shell can stimulate the right eye. Here we show that in the first two days after hatching, chicks coming from eggs incubated in the light prevalently slept with their right eye open, whereas those coming from eggs incubated in the dark prevalently slept with their left eye open. Thus, asymmetric light stimulation in the embryo can modulate the left-right direction of eye opening during post-hatching monocular sleep.     

Uncertain call likelihood negatively affects sleep and next-day cognitive performance while on-call in a laboratory environment

ABSTRACT

On-call working arrangements are employed in a number of industries to manage unpredictable events, and often involve tasks that are safety- or time-critical. This study investigated the effects of call likelihood during an overnight on-call shift on self-reported pre-bed anxiety, sleep and next-day cognitive performance. A four-night laboratory-based protocol was employed, with an adaptation, a control and two counterbalanced on-call nights. On one on-call night, participants were instructed that they would definitely be called during the night, while on the other on-call night they were told they may be called. The State-Trait Anxiety Inventory form x-1 was used to investigate pre-bed anxiety, and sleep was assessed using polysomnography and power spectral analysis of the sleep electroencephalographic analysis. Cognitive performance was assessed four times daily using a 10-min psychomotor vigilance task. Participants felt more anxious before bed when they were definitely going to be called, compared with the control and maybe conditions. Conversely, participants experienced significantly less non-rapid eye movement and stage two sleep and poorer cognitive performance when told they may be called. Further, participants had significantly more rapid eye movement sleep in the maybe condition, which may be an adaptive response to the stress associated with this on-call condition. It appears that self-reported anxiety may not be linked with sleep outcomes while on-call. However, this research indicates that it is important to take call likelihood into consideration when constructing rosters and risk-management systems for on-call workers.     

Effects of a sleep education program with self-help treatment on sleeping patterns and daytime sleepiness in Japanese adolescents: A cluster randomized trial

Subjective insufficient sleep and delayed sleep–wake patterns have been reported as the primary causes for daytime sleepiness, a reasonably significant and prevalent problem for adolescents worldwide. Systematic reviews have indicated that the success of sleep education programs has thus far been inconsistent, due to the lack of a tailored approach that allows for evaluation of individual differences in behavior patterns. One way to resolve this problem is to assess the individual sleep behaviors of adolescents by using a checklist containing the recommended behaviors for promoting sleep health. Such self-help education programs have already been implemented for elementary school children, school nurses and the elderly. The present study aimed to verify the effects of a sleep education program with supplementary self-help treatment, based on a checklist of sleep-promoting behaviors, in addition to evaluation of changes in sleeping patterns, sleep-promoting behaviors and daytime sleepiness in adolescents. A cluster randomized controlled trial involving 5 Japanese junior high schools was conducted, and 243 students (sleep education: n = 122; waiting list: n = 121; 50.6% female; 7th grade) were included in the final analysis. The sleep education group was provided with information on proper sleep health and sleep-promoting behaviors. The students in this group were asked to practice one sleep-promoting behavior as a goal for 2 weeks and to monitor their practice using sleep diaries. Both pre- and post-treatment questionnaires were administered to students in order to assess knowledge of sleep-promoting behaviors, sleeping patterns and daytime functioning. Students in the sleep education group showed significant improvement in their knowledge of sleep health (F_1,121 = 648.05, p < 0.001) and in their sleep-promoting behaviors (F_1,121 = 55.66, p < 0.001). Bedtime on both school nights (F_1,121 = 50.86, p < 0.001) and weekends (F_1,121 = 15.03, p < 0.001), sleep-onset latency (F_1,121 = 10.26, p = 0.002), total sleep time on school nights (F_1,121 = 12.45, p = 0.001), subjective experience of insufficient sleep (McNemar χ²(1) = 4.03, p = 0.045) and daytime sleepiness (McNemar χ²(1) = 4.23, p = 0.040) were also improved in the sleep education group. In contrast, no significant improvement in these variables was observed for students in the waiting-list group. In conclusion, the sleep education program with self-help treatment was effective not only in increasing sleep knowledge but also in improving sleep-promoting behavior and sleeping patterns/reducing daytime sleepiness for students in the sleep education group, in comparison with the waiting-list group.     

Changes in growth and sleep across school nights,weekends and a winter holiday period in two Australian schools

Studies suggest that there may be an association between sleep and growth; however, the relationship is not well understood. Changes in biology and external factors such as school schedule heavily impact the sleep of adolescents, during a critical phase for growth. This study assessed the changes in sleep across school days, weekends and school holidays, while also measuring height and weight changes, and self-reported alterations in food intake and physical activity. The impact of morningness–eveningness (M-E) on height change and weight gain was also investigated. In a sample of 63 adolescents (mean age = 13.13, SD = 0.33, 31 males) from two independent schools in South Australia, height and weight were measured weekly for 4 weeks prior to the school holidays and 4 weeks after the school holidays. Participants also completed a Morningness/Eveningness Scale and 7-day sleep, diet and physical activity diaries prior to, during and after the school holidays. Participants at one school had earlier wake times during the weekends than participants attending the other school, leading to a significantly shorter sleep duration on weekends for those participants. Regardless of school, sleep was significantly later and longer during the holidays (p < 0.001) and those with a stronger morning preference fell asleep (F_18,36 = 3.4, p = 0.001) and woke (F_18,44 = 2.0, p = 0.027) earlier than evening types. Growth rate was lower during the holiday weeks. For those attending the school with limited sleep in opportunities, growth after the holidays was lower for those with greater evening preference, whereas for those at the other school, growth was greater for those with greater evening preference. The increase in average weight from pre- to post-holidays was greater for those attending the school with limited opportunities to sleep longer. Participants reported greater food intake during the holidays compared to school days and greater physical activity levels on weekends compared to school days, and school days compared to holidays. Results suggest that time of day preference may impact growth, with evening types who cannot sleep in growing at a slower rate than evening types who can or morning types. This may be related to sleep restriction. Despite sleep being both later and longer during the school holidays, participants’ growth slowed during the holiday period. It is possible that this may be a reflection of other behavioural changes in the holidays (increased food intake and reduced physical activity), as sleep timing during the school period was related to growth.     

Melatonin Treatment Effects on Adolescent Students' Sleep Timing and Sleepiness in a Placebo-Controlled Crossover Study

During the last few decades, the incidence of sleep-onset insomnia, due to delay of circadian phase, has increased substantially among adolescents all over the world. We wanted to investigate whether a small dose of melatonin given daily, administered in the afternoon, could advance the sleep timing in teenagers. Twenty-one students, aged 14–19 yrs, with sleep-onset difficulties during school weeks were recruited. The study was a randomized, double blind, placebo (PL)-controlled crossover trial, lasting 5 wks. During the first 6 d in wks 2 and 4, the students received either PL or melatonin (1 mg) capsules between 16:30 and 18:00 h. During the first 6 d of wk 5, all students received melatonin. Wks 1 and 3 were capsule-free. In the last evening of each week and the following morning, the students produced saliva samples at home for later melatonin analysis. The samples were produced the same time each week, as late as possible in the evening and as early as possible in the morning. Both the student and one parent received automatic mobile text messages 15 min before saliva sampling times and capsule intake at agreed times. Diaries with registration of presumed sleep, subjective sleepiness during the day (Karolinska Sleepiness Scale, KSS) and times for capsule intake and saliva samplings were completed each day. Primary analysis over 5 wks gave significant results for melatonin, sleep and KSS. Post hoc analysis showed that reported sleep-onset times were advanced after melatonin school weeks compared with PL school weeks (p < .005) and that sleep length was longer (p < .05). After the last melatonin school week, the students fell asleep 68 min earlier and slept 62 min longer each night compared with the baseline week. Morning melatonin values in saliva diminished compared with PL (p < .001) and evening values increased (p < .001), indicating a possible sleep phase advance. Compared with PL school weeks, the students reported less wake up (p < .05), less school daytime sleepiness (p < .05) and increased evening sleepiness (p < .005) during melatonin weeks. We conclude that a small dose of melatonin given daily, administered in the afternoon, could advance the sleep timing and make the students more alert during school days even if they continued their often irregular sleep habits during weekends. (Author correspondence: arne.lowden@stress.su.se)     

Recovery of Cognitive Performance from Sleep Debt: Do a Short Rest Pause and a Single Recovery Night Help?

We studied the recovery of multitask performance and sleepiness from acute partial sleep deprivation through rest pauses embedded in performance sessions and an 8 h recovery sleep opportunity the following night. Sixteen healthy men, aged 19–22 yrs, participated in normal sleep (two successive nights with 8 h sleep) and sleep debt (one 2 h night sleep followed by an 8 h sleep the following night) conditions. In both conditions, the participants performed four 70 min multitask sessions, with every other one containing a 10 min rest pause with light neck‐shoulder exercise. The multitask consisted of four simultaneously active subtasks, with the level of difficulty set in relation to each participant's ability. Physiological sleepiness was assessed with continuous electroencephalography/electro‐oculography recordings during the multitask sessions, and subjective sleepiness was self‐rated with the Karolinska Sleepiness Scale. Results showed that multitask performance and physiological and subjective sleepiness were impaired by the sleep debt (p>.001). The rest pause improved performance and subjective sleepiness for about 15 min, regardless of the amount of prior sleep (p>.01–.05). Following recovery sleep, all outcome measures showed marked improvement (p<.001), but they failed to reach the levels observed in the control condition (p<.001–.05). A correlation analysis showed the participants whose multitask performance deteriorated the most following the night of sleep loss tended to be the same persons whose performance was most impaired following the night of the recovery sleep (p<.001). Taken together, our results suggest that a short rest pause with light exercise is not an effective countermeasure in itself for sleep debt‐induced impairments when long‐term effects are sought. In addition, it seems that shift arrangements that lead to at least a moderate sleep debt should be followed by more than one recovery night to ensure full recovery. Persons whose cognitive performance is most affected by sleep debt are likely to require the most sleep to recover.     

Orangutans (Pongo spp.) have deeper,more efficient sleep than baboons (Papio papio) in captivity

The nightly construction of arboreal sleeping platforms or “nests” has been observed among every great ape population studied to date. However, this behavior has never been reported in any other nonhuman primate and comparisons between ape and monkey sleep illuminate the link between sleeping substrates, positional behavior, and sleep efficiency. Here, we compare sleep depth and efficiency and night‐time positional behavior between a large‐bodied cercopithecoid (Papio papio) and a large‐bodied hominoid (Pongo spp.) at the Indianapolis Zoo. We used infrared videography to assess nightly sleep and awake behavioral states, gross body movements, and postures in baboons (N = 45 nights) and orangutans (N = 128 nights). We calculated the total waking time, total sleep time, sleep fragmentation (the number of brief awakenings ≥2 min/h), sleep motor activity (number of motor activity bouts per hour), sleep efficiency (sleep duration/time in bed), and percentage of time spent in each posture. By every measure, orangutans experienced overall deeper, more efficient sleep. Baboons were more likely to sleep in guarded, upright positions (weight bearing on their ischial callosities) and never opted to use additional materials to augment sleep environments, whereas orangutans slept in insouciant, relaxed positions on constructed sleeping materials. Our results suggest that relaxed sleeping postures may have been enabled by sleeping platforms as a behavioral facilitator to sleep, which could have allowed for greater sleep depth and next‐day cognitive capacities in both great apes and hominins. Am J Phys Anthropol 157:421–427, 2015. © 2015 Wiley Periodicals, Inc.     

Relationship between sleep and eye state in Cetaceans and Pinnipeds

We recorded EEG from both hemispheres and documented the state of the two eyes in two species of Cetaceans (one beluga and one bottlenose dolphin) and one species of Pinnipeds (two northern fur seals). In the dolphin and beluga we found that episodes of unihemispheric slow wave sleep (USWS) were associated with asymmetry in eye state. During USWS and asymmetrical SWS the eye contralateral to the sleeping hemisphere was mostly closed or in an intermediate state while the eye contralateral to the waking hemisphere was more often open or in an intermediate state. Bilateral eye opening indicated waking in about 80% cases and unilateral eye closure indicated USWS with an accuracy of about 75%. Bilateral eye closure was rare (< 2% of the observation time) and was not necessarily associated with high amplitude SWS. In fur seals, episodes of one eye briefly opening usually occurred in the beginning of sleep episodes and lasted several minutes. Those episodes were frequently associated with lower amplitude EEG slow waves in the contralateral brain hemisphere. During most of their sleep on land, fur seals had both eyes tightly closed. No EEG asymmetry was recorded at this time. Although eye state and EEG stage are correlated in the bottlenose dolphin, beluga and fur seals, short episodes of EEG synchrony (less then 1 min) occur contralateral to an open eye and waking (a more activated EEG) activity can be present contralateral to a closed eye. The available data suggest that two functions of USWS/EEG asymmetry during SWS in Cetaceans and fur seals are multisensory control of the environment and maintenance of motion and postures of sleep. The adaptive advantages of USWS throughout the evolution of Cetaceans and Pinnipeds from terrestrial mammals to present forms could include 1) the avoidance of predators and maintenance of contact with other animals of the same species; 2) continuance of regular breathing; 3) and effective thermoregulation in the water environment.     

Social jet lag,chronotype and body mass index in 14–17-year-old adolescents

The relationship between sleep duration and obesity in adolescents is inconclusive. This may stem from a more complex relationship between sleep and obesity than previously considered. Shifts toward evening preferences, later sleep–wake times and irregular sleep–wake patterns are typical during adolescence but their relationship to body mass index (BMI) has been relatively unexplored. This cross-sectional study examined associations between sleep duration, midpoint of sleep and social jet lag (estimated from 7 days of continuous actigraphy monitoring), and morningness/eveningness with BMIs (BMI z-scores) and waist-to-height ratios in 14–17-year-old adolescents. Seventy participants were recruited from ninth and tenth grades at a public high school. Participants’ characteristics were as follows: 74% female, 75% post-pubertal, 36% Hispanic, 38% White, 22% Black, 4% Asian and 64% free/reduced lunch participants with a mean age of 15.5 (SD, 0.7). Forty-one percent of the participants were obese (BMI ≥ 95th percentile); 54% were abdominally obese (waist-to-height ratio ≥ 0.5). Multivariable general linear models were used to estimate the association between the independent variables (school night sleep duration, free night sleep duration, midpoint of sleep (corrected), social jet lag and morningness/eveningness) and the dependent variables (BMI z-scores and waist-to-height ratios). Social jet lag is positively associated with BMI z-scores (p < 0.01) and waist-to-height ratios (p = 0.01). Midpoint of sleep (corrected) is positively associated with waist-to-height ratios (p = 0.01). After adjusting for social jet lag, school night sleep duration was not associated with waist-to-height ratios or BMI z-scores. Morningness/eveningness did not moderate the association between sleep duration and BMI z-scores. Findings from this study suggest that chronobiological approaches to preventing and treating obesity may be important for accelerating progress in reducing obesity rates in adolescents.     

Sleep duration and social jetlag are independently associated with anxious symptoms in adolescents

Although short total sleep time (TST) is associated with increased anxious symptoms in adolescents, it is unknown whether social jetlag, a misalignment between sleep timing on the weekend and school week, is independently associated with anxious symptoms. In the current study, sleep timing, anxious symptoms, and demographic information were assessed from 3097 adolescents (48% female, mean ± SD age 15.59 ± .77 years) from the age 15 wave of the Fragile Families and Child Wellbeing Study. Social jetlag was calculated as the absolute value of the midpoint of sleep on the weekend minus the midpoint of sleep during the school week. Anxious symptoms were measured through the 6-item anxiety subscale of the Brief Symptom Inventory 18. We assessed associations between sleep variables and anxious symptoms using multiple linear regression. Adjusted analyses controlled for sex, race/ethnicity, age in years, body mass index percentile, number of other children below the age of 18 in the household, and primary caregiver (PCG) married/cohabiting with youth’s biological parent, PCG employment status, PCG household income and PCG education level. In fully adjusted models (R² = .034), school night TST (b = ?.04, ?R² = .005, p < .001) was negatively associated with anxiety symptoms, while social jetlag (b = .04, ?R² = .009, p < .001) was positively and independently associated with anxiety symptoms. Findings indicate small associations of school night TST and social jetlag with anxious symptoms. Thus, maintenance of optimal emotional health in adolescents may require both sufficient sleep duration and regularity of sleep timing across the week.     

Sleep Patterns of Day-Working,Evening High-Schooled Adolescents of São Paulo,Brazil

Children who grow up in developing countries of the world must work to help financially support their families, and they must also attend school. We investigated the impact of work on the sleep of working vs. nonworking high school students. Twenty-seven São Paulo, Brazil, public high school students (eight male and eight female working students plus six nonworking female and five nonworking male students) 14–18 yrs of age who attended school Monday–Friday between 19:00 to 22:30 h participated. A comprehensive questionnaire about work and living conditions, health status, and diseases and their symptoms was also answered. The activity level and rest pattern (sleep at night and napping during the day) were continuously assessed by wrist actigraphy (Ambulatory Monitoring, USA). The main variables were analyzed by a two-factor ANOVA with application of the Tukey HSD test for multiple comparisons, and the length of sleep during weekdays vs. weekends was compared by Student t-test. Working students went to sleep earlier weekends [F_(1,23) = 6.1; p = 0.02] and woke up earlier work days than nonworking students [F_(1,23) = 17.3; p = 0.001]. The length of nighttime sleep during weekdays was shorter among all the working [F_(1,23) = 16.7; p < 0.001] than all the nonworking students. The sleep duration of boys was shorter than of girls during weekends [F_(1,23) = 10.8; p < 0.001]. During weekdays, the duration of napping by working and nonworking male students was shorter than nonworking female students. During weekdays, working girls took the shortest naps [F_(1,23) = 5.6; p = 0.03]. The most commonly reported sleep complaint during weekdays was difficulty waking up in the morning [F_(1,23) = 6.5; p = 0.02]. During weekdays, the self-perceived sleep quality of working students was worse than nonworking students [F_(1,23) = 6.2; p = 0.02]. The findings of this study show that work has negative effects on the sleep of adolescents, with the possible build-up of a chronic sleep debt with potential consequent impact on quality of life and school learning.     

An EEG study of different behavioral states of freely moving dolphins]

ECoG and EMG of neck and eye muscles of four free moving dolphins were recorded during sleep-wakefulness cycle through chronically implanted electrodes. Wakefulness is accompanied by desynchronized ECoG, and slow sleep by synchronized ECoG, including the sleep spindles and theta- and delta-waves. The standard EMG criteria do not allow the discrimination between fast sleep and wakefulness in dolphins. Behavioral observations alone do not inform about dolphin's sleep or wakefulness. The respiration of dolphins may be observed during bilateral ECoG synchronization in slow sleep without arousal. ECoG synchronization as well as desynchronization may be observed when the contralateral eye is open.     

miR-155 deletion modulates lipopolysaccharide-induced sleep in female mice

Immune signaling is known to regulate sleep. miR-155 is a microRNA that regulates immune responses. We hypothesized that miR-155 would alter sleep regulation. Thus, we investigated the potential effects of miR-155 deletion on sleep-wake behavior in adult female homozygous miR-155 knockout (miR-155^KO) mice and littermate controls (WT). Mice were implanted with biotelemetry units and EEG/EMG biopotentials were recorded continuously for three baseline days. miR-155^KO mice had decreased bouts of NREM and REM sleep compared with WT mice, but no differences were observed in the length of sleep bouts or total time spent in sleep-wake states. Locomotor activity and subcutaneous temperature did not differ between WT and miR-155^KO mice. Following baseline recordings, mice were sleep-deprived during the first six hours of the rest phase (light phase; ZT 0–6) followed by an 18 h recovery period. There were no differences between groups in sleep rebound (% sleep and NREM δ power) after sleep deprivation. Following recovery from sleep deprivation, mice were challenged with a somnogen (viz., lipopolysaccharide (LPS)) one hour prior to the initiation of the dark (active) phase. Biopotentials were continuously recorded for the following 24 h, and miR-155^KO mice displayed increased wakefulness and decreased NREM sleep during the dark phase following LPS injection. Additionally, miR-155^KO mice had reduced EEG slow-wave responses (0.5–4 Hz) compared to WT mice. Together, our findings indicate that miR-155 deletion attenuates the somnogenic and EEG delta-enhancing effects of LPS.

Abbreviations: ANOVA: analysis of variance; EEG: electroencephalogram; EMG: electromyogram; h: hour; IL-1: interleukin-1; IL-6: interleukin-6; IP: intra-peritoneal; LPS: lipopolysaccharide; miR/miRNA: microRNA; miR-155^KO: miR-155 knockout; NREM: non-rapid eye movement; REM: rapid eye movement; TNF: tumor necrosis factor; SWS: slow-wave sleep; WT: wild-type.     

Sleep duration varies as a function of glutamate and GABA in rat pontine reticular formation

The oral part of the pontine reticular formation (PnO) is a component of the ascending reticular activating system and plays a role in the regulation of sleep and wakefulness. The PnO receives glutamatergic and GABAergic projections from many brain regions that regulate behavioral state. Indirect, pharmacological evidence has suggested that glutamatergic and GABAergic signaling within the PnO alters traits that characterize wakefulness and sleep. No previous studies have simultaneously measured endogenous glutamate and GABA from rat PnO in relation to sleep and wakefulness. The present study utilized in vivo microdialysis coupled on-line to capillary electrophoresis with laser-induced fluorescence to test the hypothesis that concentrations of glutamate and GABA in the PnO vary across the sleep/wake cycle. Concentrations of glutamate and GABA were significantly higher during wakefulness than during non-rapid eye movement sleep and rapid eye movement sleep. Regression analysis revealed that decreases in glutamate and GABA accounted for a significant portion of the variance in the duration of non-rapid eye movement sleep and rapid eye movement sleep episodes. These data provide novel support for the hypothesis that endogenous glutamate and GABA in the PnO contribute to the regulation of sleep duration.     

EEG Correlates of Dream Recall in Depressed Outpatients and Healthy Controls

The present study explored EEG correlates of dream recall in 17 symptomatic, unmedicated depressed patients and in 19 healthy adults. EEG segments from the last 30 minutes of sleep, from the five minutes following morning awakening, and the absolute difference between sleep and waking EEG were contrasted between the two groups of participants during successful dream recall and during no recall. Period amplitude analysis was used to quantify EEG frequencies. Increased high-frequency beta incidence in the right hemisphere and amplitude in both hemispheres during sleep were associated with dream recall in both patient and control groups. Depressed patients also showed higher delta amplitude in both hemispheres during sleep associated with recall, but this effect did not reach significance. With regard to the changes between sleep and wakefiilness, a smaller change in right hemisphere beta and delta incidence characterized successful recall in healthy controls. By contrast, those with depression showed recall success when the sleep/wake shifts in right hemisphere beta and delta incidence were larger. Recall failure was characterized by small EEG shifts from sleep to wakefulness in the depressed group. The same effects were observed for beta and delta amplitude measures, except that healthy controls showed a large shift in delta amplitude in the sleep-wake transition during successful recall but not during recall failure. Recall in those with depression was associated with a dramatic shift in left hemisphere delta amplitude. These findings provide support for Koukkou and Lehmann's (1983, 1993) state-shift hypothesis of dream recall in healthy controls (except for left hemisphere delta amplitude) but not in the depressed. It appears that in order to recall a dream, depressed patients must undergo larger shifts in brain activity and perhaps a different pattern of reorganization of EEG frequencies than controls. This finding may account for the low rates of recall reported previously in this clinical group.     

Efficient and Regular Patterns of Nighttime Sleep are Related to Increased Vulnerability to Microsleeps Following a Single Night of Sleep Restriction

Sleep-deprived people, or those performing extended monotonous tasks, can exhibit brief episodes in which they suspend performance and appear to fall asleep momentarily—behavioral microsleeps (“microsleeps”). In this study, microsleeps were identified using eye video and tracking response during a 20-min continuous tracking task undertaken by 16 healthy volunteers (mean age 24.9?yrs; 8 females, 8 males) in the early afternoon following a normally rested night and a night of restricted sleep (time-in-bed restricted to 4?h). Sessions were 1 wk apart and counterbalanced. Wrist actigraphy, self-reported sleepiness, and sleep quality were also recorded. We hypothesized that high microsleep rates when normally rested or after a night of sleep restriction would be related to poor sleep quality, sleep disturbance, circadian type, irregular sleep patterns, low daily sleep duration, or poor sleep efficiency. We also hypothesized that prior performance on a 10-min psychomotor vigilance task (PVT) (mean reaction time or number of PVT lapses) would be related to the number of microsleeps during the tracking task and that PVT performance could, therefore, be used as a fitness-for-duty indicator. The number of microsleeps during the tracking task increased following sleep restriction (mean 11.4 versus 27.9; p?=?0.03). There were no correlations between the number of microsleeps in the normally rested session and any of the actigraphically measured or self-reported sleep measures. However, the number of microsleeps following sleep restriction was correlated with sleep efficiency (r?=?0.73, p?=?0.001), sleep onset latency (r?=??0.57, p?=?0.02), and sleep onset time-of-day standard deviation (r?=??0.54, p?=?0.03) over 11 normally rested nights. There was no correlation between PVT performance and the subsequent number of microsleeps during the tracking task in either session. Attributes usually associated with beneficial nighttime sleep patterns—going to sleep at a similar time each night, falling asleep quickly, and infrequent arousals—were related to greater vulnerability to microsleeps following sleep restriction. There were intercorrelations between all the sleep measures associated with microsleep rate following sleep restriction, indicating that the measures form a pattern of behaviors and are not independently related to microsleep rate. Perhaps some people maintain a regular sleep pattern because they experience sleepiness the following day when their pattern is disrupted. Conversely, people with more variation in their sleep pattern may do so because this does not substantially increase sleepiness the following day. We conclude that people with consistent sleep patterns and efficient sleep may be more prone to microsleeps than other people when their usual regular pattern is disrupted by sleep restriction.