The Cognitive Social Network in Dreams: Transitivity,Assortativity, and Giant Component Proportion Are Monotonic

For five individuals, a social network was constructed from a series of his or her dreams. Three important network measures were calculated for each network: transitivity, assortativity, and giant component proportion. These were monotonically related; over the five networks as transitivity increased, assortativity increased and giant component proportion decreased. The relations indicate that characters appear in dreams systematically. Systematicity likely arises from the dreamer's memory of people and their relations, which is from the dreamer's cognitive social network. But the dream social network is not a copy of the cognitive social network. Waking life social networks tend to have positive assortativity; that is, people tend to be connected to others with similar connectivity. Instead, in our sample of dream social networks assortativity is more often negative or near 0, as in online social networks. We show that if characters appear via a random walk, negative assortativity can result, particularly if the random walk is biased as suggested by remote associations.     

Differential effects of driver sleepiness and sleep inertia on driving behavior

ObjectivesDriver sleepiness is one of the major safety issues in conventional driving and sleep inertia emerges as a driver state in automated driving. The aim of the present study was to assess the differential impacts of sleepiness and sleep inertia on driving behavior.Method61 participants completed a 10-min manual driving task during an otherwise automated drive. They completed the task (a) under an alert state, (b) under a sleepy state, and (c) after EEG-confirmed sleep. Driving performance was assessed with the parameters lane-keeping, speed choice, and speed-keeping. The eye-blink-based sleepiness measure PERCLOS (the proportion of time with eyes closed) was compared for the three driver states.ResultsLane- and speed-keeping performance were impaired under the sleepy state and after sleep, relative to the alert state. After sleep, lane-keeping behavior recovered rapidly and speed-keeping recovered by trend. Under the sleepy state, performance deteriorated. After sleep, the mean speed was lower than in the sleepy state and in the alert state. PERCLOS was increased after sleep and under the sleepy state, relative to the alert state.ConclusionsAlthough sleep inertia had detrimental effects on driving parameters similar to sleepiness, this effect rapidly vanished. Hence, while brief naps might be suitable to restore alertness in general, the minimal time needed to regain full capacity after napping should be a focus of future research.     

Culture and the organization of infant sleep: A study in the Netherlands and the U.S.A.

This study investigates differences in the amount and structure of infant sleep in two cultural places with previously documented, divergent parental beliefs and practices. Eight-month-old infants (n = 24 per site) were recruited from towns in the Netherlands and the eastern U.S.A. To evaluate sleep, infants’ physical activity was recorded at home for 24 h using a miniature actigraph, while parents kept a diary of infant activities. Measures derived from actigraphy include total sleep, longest sleep episode, longest wake episode, number of sleep episodes, and percent of sleep during nighttime, as well as time in the stages of Quiet and Active Sleep. Measures based on the parental diaries include most of these aspects as well, except those related to sleep stages. Results based on the more precise actigraphy method indicate that (1) the Dutch infants averaged 13.65 h of sleep per 24 h, 1.67 h more than the U.S. infants; this difference was mostly due to daytime sleep; (2) The Dutch infants’ longest wake episode averaged less than that of the U.S. infants, while their longest sleep episode appeared slightly longer. (3) The Dutch infants, compared to the U.S. sample, spent more time in the Quiet, rather than the Active phase of sleep; (4) They began their Quiet sleep earlier in the evening than did their U.S. counterparts. Measures derived from parental diaries are largely in agreement with the actigraph findings. These results are consistent with reported and observed practices and beliefs in the two communities. The pattern of differences – less apparent maturity among the Dutch in the amount of sleep, but greater apparent maturity in the structure of sleep -- illustrates that behavioral and neurological maturity can be assessed only in the context of the developing child’s adaptation to the specific demands and affordances of the culturally structured developmental niche.     

Temperament and sleep behaviors in infants and toddlers living in low-income homes

Temperament is a dynamic trait that can be shaped by maturity and environmental experiences. In this study, we sought to determine whether and the extent to which temperament was predicted by sleeping behaviors in an understudied sample of primarily Black and White infants and toddlers living in low-income homes (N = 150). Sleeping behaviors were assessed at 15–19 months of age with caregiver report of the Tayside Children’s Sleep Questionnaire. Temperament was examined as effortful control, negativity, and surgency with the Infant Behavior Questionnaire Very Short Form at 9–12 months of age and with the Early Childhood Behavior Questionnaire Short Form at 20–24 months of age. Covariates were maternal education, household income, and child sex and race. Continuous variables were standardized, then missing data from independent variables were multiply imputed in 20 datasets. Regression analyses showed that about 1 SD improvement in toddler sleep behaviors significantly predicted about 1/5 SD better toddler effortful control. However, sleep behaviors did not significantly predict toddler surgency or negative affect. This study shows that for a sample of infants and toddlers in low-income homes, how a child learns to regulate sleeping behaviors may influence the development of overall effortful control about six months later.     

Effects of daily maladaptive coping on nightly sleep in mothers

Objective: We examined effects of daily rumination and suppression in response to stressors on objective and subjective sleep among mothers.

Design: Participants were 183 mothers, including chronically stressed mothers of children with an autism spectrum disorder (M-ASD; n = 92) and age-matched mothers of neurotypical children (M-NT; n = 91). In an intensive longitudinal design, participants provided reports of daily rumination and suppression, nightly objective actigraphy-defined sleep and nightly subjective sleep quality for seven consecutive days at baseline, 9 months and 18 months.

Main Outcome Measures: Total sleep time, sleep fragmentation, sleep onset latency, and subjective sleep quality.

Results: Among M-NT with above average depressive symptoms, higher daily rumination was associated with shorter total sleep time. Rumination was associated with more sleep fragmentation among M-NT at the trend level. Rumination was not associated with sleep onset latency among M-NT, or with any sleep outcomes among M-ASD. Suppression was not associated with any sleep outcomes.

Conclusion: We provide novel evidence of the effect of rumination on objectively measured sleep duration among M-NT. Coping was not related to sleep among M-ASD. Given the prevalence of poor sleep among mothers, future work should examine modifiable factors perpetuating sleep disturbance.     

Sleep interventions for performance,mood and sleep outcomes in athletes: A systematic review and meta-analysis

Sleep is fundamental to sports performance and other health outcomes such as mental wellbeing. This systematic review explored the effects of sleep interventions implemented among athletes on performance, sleep, and mood outcomes. Five databases were searched, returning 5996 records for screening. Of these, 27 articles met the inclusion criteria (16 controlled deigns, 11 uncontrolled; athletes n = 617; male n = 432, female n = 93, non-binary/other n = 0 or not reported n = 92). Narrative synthesis of all studies based on intervention type suggested that sleep hygiene, assisted sleep, and sleep extension interventions may be associated with improved sleep, performance, and mood outcomes. Twelve controlled trials were eligible for quantitative meta-analysis, investigating the effect of sleep interventions on athlete sleep, performance, and negative affect, compared to controls post-intervention. Utilizing random-effects meta-analyses, sleep interventions improved subjective sleep quality (g = 0.62, 95% CI [0.21, 1.02]), reduced sleepiness (g = 0.81, 95% CI [0.32, 1.30]) and decreased negative affect (g = 0.63, 95% CI [0.27, 0.98]), but did not appear to influence subjective sleep duration. No effects were identified for objective sleep measures (e.g., actigraphy), or aerobic/anaerobic performance indices. While sleep interventions may offer some benefit to athletes, caution is warranted given limitations of the extant research relating to small, non-representative studies with methodological concerns.     

The effect of a delayed weekend sleep pattern on sleep and morning functioning

Abstract

It is a common practice for young adults to delay their weekend sleep schedule. The present study was designed to assess the effect of this sleep pattern on the sleep of Sunday night and the functioning of Monday morning. The sleep schedules of 30 young adults were manipulated for 2 consecutive weeks. In the Habitual-Sleep (HS) week, subjects followed their habitual sleep schedule throughout the week; in the Delayed-Sleep (DS) week, subjects' sleep schedule on Friday and Saturday nights were delayed by two hours. Compared to the HS week, subjects showed significantly lower subjective sleepiness near bedtime and trends of longer sleep onset latency on Sunday night in the DS week. In addition, there was both lowered cognitive performance and overall mood rating on Monday morning in the DS week. The delayed weekend sleep pattern contributes to Sunday night insomnia and the Monday morning “blues”.