Self-reported physical activity and sleep quality is associated with working memory function in middle-aged and older adults during the COVID-19 pandemic.

While previous work has shown a positive relationship between cognitive performance and lifestyle factors in younger adults, evidence for this relationship among middle-aged and older adults has been mixed. The current study aimed to further test the relationship among physical activity, sleep quality, and memory performance in middle-aged and older adults, and to test whether this relationship holds up during the COVID-19 pandemic. Our results showed that physical activity was associated with better sleep quality and better working memory performance, and better sleep quality was associated with better working memory and self-perceptions of everyday memory abilities. Additionally, we found that the effects of physical activity on working memory were partially mediated by sleep quality. While these effects were small and only correlational in nature, they lend further support to the notion that sleep quality and physical activity are beneficial to memory later in life, even during a global pandemic.

Contributions of post-learning REM and NREM sleep to memory retrieval.

It has become clear that sleep after learning has beneficial effects on the later retrieval of newly acquired memories. The neural mechanisms underlying these effects are becoming increasingly clear as well, particularly those of non-REM sleep. However, much is still unknown about the sleep and memory relationship: the sleep state or features of sleep physiology that associate with memory performance often vary by task or experimental design, and the nature of this variability is not entirely clear. This paper describes pertinent features of sleep physiology and provides a detailed review of the scientific literature indicating beneficial effects of post-learning sleep on memory retrieval. This paper additionally introduces a hypothesis which attributes these beneficial effects of post-learning sleep to separable processes of memory reinforcement and memory refinement whereby reinforcement supports one's ability to retrieve a given memory and refinement supports the precision of that memory retrieval in the context of competitive alternatives. It is observed that features of non-REM sleep are involved in a post-learning substantiation of memory representations that benefit memory performance; thus, memory reinforcement is primarily attributed to non-REM sleep. Memory refinement is primarily attributed to REM sleep given evidence of bidirectional synaptic plasticity in REM sleep and findings from studies of selective REM sleep deprivation.

The role of pubertal status and sleep satisfaction in emotion reactivity and regulation in children and adolescents.

Study Objectives: This study investigated the role of pubertal status and hormones in the association between sleep satisfaction and self-reported emotion functioning in 256 children and adolescents aged 8-15. Methods: Self-report data was provided on sleep duration, sleep satisfaction, and emotion reactivity and regulation, and a saliva sample was obtained for hormone measures. A subset of children also wore an Actigraph watch to measure sleep for a week. Results: Latent-class analysis revealed three classes of sleepers: Satisfied, Moderately Satisfied, and Dissatisfied. Dissatisfied sleepers reported more difficulties with emotion regulation and greater emotion reactivity than Satisfied sleepers. High difficulties with emotion regulation was associated with shorter objective sleep duration, and high emotion reactivity was associated with lower sleep efficiency. For girls, Dissatisfied sleepers reported being further through pubertal development than Satisfied sleepers. There were also significant correlations between pubertal development and shorter sleep duration and longer sleep latency in girls, and shorter and more irregular sleep in boys. Finally, pubertal development in girls was a significant moderator in the relationship between sleep satisfaction and difficulties with emotion regulation in Dissatisfied sleepers, such that being further through puberty and having unsatisfactory sleep resulted in the highest emotion regulation difficulties. Conclusions: This study expands on previous literature by considering the role of sleep satisfaction and the interaction with puberty development on emotion function. Specifically, a role for pubertal development was identified in the association between unsatisfactory sleep and emotion regulation in girls.

Hyperarousal Is Associated with Socioemotional Processing in Individuals with Insomnia Symptoms and Good Sleepers.

Despite complaints of difficulties in waking socioemotional functioning by individuals with insomnia, only a few studies have investigated emotion processing performance in this group. Additionally, the role of sleep in socioemotional processing has not been investigated extensively nor using quantitative measures of sleep. Individuals with insomnia symptoms (n = 14) and healthy good sleepers (n = 15) completed two nights of at-home polysomnography, followed by an afternoon of in-lab performance testing on tasks measuring the processing of emotional facial expressions. The insomnia group self-reported less total sleep time, but no other group differences in sleep or task performance were observed. Greater beta EEG power throughout the night was associated with higher intensity ratings of happy, fearful and sad faces for individuals with insomnia, yet blunted sensitivity and lower accuracy for good sleepers. Thus, the presence of hyperarousal differentially impacted socioemotional processing of faces in individuals with insomnia symptoms and good sleepers.

Sleep restriction alters reactive aggressive behavior and its relationship with sex hormones.

Few studies have experimentally manipulated sleep to study its effect on aggressive behavior. The current study examined how reactive aggression was affected by having sleep restricted to 4-hours on a single night, a level of disruption commonly experienced. Both rested and sleep-restricted participants completed the Point Subtraction Aggression Paradigm (PSAP), a laboratory task in which participants seek to earn points, are provoked by a fictitious opponent stealing their points, and may choose to steal points in response. Logistic mixed-effect models were used to investigate the effect of sleep restriction and the role of sex hormones on the odds of choosing to steal. For men, and women in the luteal phase of the menstrual cycle, sleep restriction did not result in significant changes reactive aggression, although the patterns of aggressive behavior appeared less reactive and retaliatory in nature. For women in the follicular phase of the menstrual cycle, sleep restriction was associated with higher levels of reactive aggression. For both men and women in the luteal phase, sleep restriction disrupted an association between hormone change over the task (testosterone and estradiol, respectively) and reactive aggression that was observed in their control participants. In addition, higher testosterone before the PSAP in men was associated with maintaining a high level of stealing over the task. These results indicate a complex dynamic in which sex hormones and sleep interact to predict aggressive behavior in response to provocation.

Changes in EEG multiscale entropy and power-law frequency scaling during the human sleep cycle.

We explored changes in multiscale brain signal complexity and power-law scaling exponents of electroencephalogram (EEG) frequency spectra across several distinct global states of consciousness induced in the natural physiological context of the human sleep cycle. We specifically aimed to link EEG complexity to a statistically unified representation of the neural power spectrum. Further, by utilizing surrogate-based tests of nonlinearity we also examined whether any of the sleep stage-dependent changes in entropy were separable from the linear stochastic effects contained in the power spectrum. Our results indicate that changes of brain signal entropy throughout the sleep cycle are strongly time-scale dependent. Slow wave sleep was characterized by reduced entropy at short time scales and increased entropy at long time scales. Temporal signal complexity (at short time scales) and the slope of EEG power spectra appear, to a large extent, to capture a common phenomenon of neuronal noise, putatively reflecting cortical balance between excitation and inhibition. Nonlinear dynamical properties of brain signals accounted for a smaller portion of entropy changes, especially in stage 2 sleep.

Influence of sleep on developing brain functions and structures in children and adolescents: A systematic review.

This systematic review examined the associations between sleep and brain functions and structures in children and adolescents aged 1-17 ys. Included studies (n = 24) were peer-reviewed and met the a priori determined population (apparently healthy children and adolescents aged 1 y to 17 ys), intervention/exposure/comparator (various sleep characteristics including duration, architecture, quality, timing), and outcome criteria (brain functions and/or brain structures, excluding cognitive function outcomes). Collectively, the reviewed studies report some relationships between inadequate sleep and resultant differences in brain functions or structures. Although the research presented supports and offers more insight into the importance of sleep for the developing brain of children and adolescents, no firm conclusions that apply broadly may be drawn from these results, particularly because of the diversity of the sleep variables and outcomes. However, it is clear that sleeping habits in the pediatric population should be prioritized. Health care providers should continue to recommend healthy sleep practices and adequate time for sleep, as they are essential for overall health, including brain health.

A daytime nap enhances visual working memory performance and alters event-related delay activity.

Working memory (WM) is impaired following sleep loss and may be improved after a nap. The goal of the current study was to better understand sleep-related WM enhancement by: (1) employing a WM task that assesses the ability to hold and report visual representations as well as the fidelity of the reports on a fine scale, (2) investigating neurophysiological properties of sleep and WM capacity as potential predictors or moderators of sleep-related enhancement, and (3) exploring frontal and occipital event-related delay activity to index the neural processing of stimuli in WM. In a within-subjects design, 36 young adults (Mage = 20, 20 men, 16 women) completed a 300-trial, continuous-report task of visual WM following a 90-min nap opportunity and an equivalent period of wakefulness. Mixed-effect models were used to estimate the odds of successful WM reports and the fidelity of those reports. The odds of a successful report were approximately equal between nap and wake conditions for the start of the task, but by the end, the odds of success were 1.26 times greater in the nap condition. Successful WM reports were more accurate after a nap, independent of the time on task. Neither WM capacity nor any of the sleep variables measured were found to significantly moderate the nap effect on WM. Lastly, napping resulted in amplitude changes for frontal and occipital delay activity relative to the wake condition. The findings are discussed in relation to contemporary models of visual WM and the role of sleep in sustained attention.

Sleep physiology predicts memory retention after reactivation.

Both sleep and future relevance influence memory consolidation; however, limited research has investigated their role in memory reconsolidation. We manipulated the future relevance of both stable and labile memories in need of reconsolidation. Two groups learned two blocks of syllable pairs on one evening and were told they would be tested on one of the blocks later. On the second evening, one group (Labile) received reminders designed to return their memories of syllable pairs to a labile state, while a second group (Stable) received reminders designed to leave these memories in a stable state. No significant differences in memory retention were found between blocks or groups the following morning. Frontal delta (0.5-4 Hz) electroencephalographic power during Stage 2 sleep correlated positively with retention of future-relevant material exclusively in the Labile group. Central theta (4-8 Hz) electroencephalographic power during rapid eye movement (REM) sleep correlated positively with the extent to which the Labile group selectively retained future-relevant material. These relationships suggest that sleep-dependent processes are involved in an economical reprocessing of memories beyond the initial stages of consolidation.

Performance monitoring following total sleep deprivation: effects of task type and error rate.

There is a need to understand the neural basis of performance deficits that result from sleep deprivation. Performance monitoring tasks generate response-locked event-related potentials (ERPs), generated from the anterior cingulate cortex (ACC) located in the medial surface of the frontal lobe that reflect error processing. The outcome of previous research on performance monitoring during sleepiness has been mixed. The purpose of this study was to evaluate performance monitoring in a controlled study of experimental sleep deprivation using a traditional Flanker task, and to broaden this examination using a response inhibition task. Forty-nine young adults (24 male) were randomly assigned to a total sleep deprivation or rested control group. The sleep deprivation group was slower on the Flanker task and less accurate on a Go/NoGo task compared to controls. General attentional impairments were evident in stimulus-locked ERPs for the sleep deprived group: P300 was delayed on Flanker trials and smaller to Go-stimuli. Further, N2 was smaller to NoGo stimuli, and the response-locked ERN was smaller on both tasks, reflecting neurocognitive impairment during performance monitoring. In the Flanker task, higher error rate was associated with smaller ERN amplitudes for both groups. Examination of ERN amplitude over time showed that it attenuated in the rested control group as error rate increased, but such habituation was not apparent in the sleep deprived group. Poor performing sleep deprived individuals had a larger Pe response than controls, possibly indicating perseveration of errors. These data provide insight into the neural underpinnings of performance failure during sleepiness and have implications for workplace and driving safety.

Sleep deprivation lowers reactive aggression and testosterone in men.

The role of sleep deprivation in aggressive behavior has not been systematically investigated, despite a great deal of evidence to suggest a relationship. We investigated the impact of 33 h of sleep loss on endocrine function and reactive aggression using the Point Subtraction Aggression Paradigm (PSAP) task. PSAP performance was assessed in 24 young men and 25 women who were randomly assigned to a sleep deprivation or control condition. Sleep deprivation lowered reactive aggression and testosterone (but not cortisol) in men, and disrupted the positive relationship between a pre-post PSAP increase in testosterone and aggression that was evident in rested control men. While women increased aggression following provocation as expected, no influence of sleep deprivation was found. This is the first experimental study to demonstrate that sleep deprivation lowers reactive aggression in men. Testosterone, but not cortisol, played a role in the relationship between sleep and reactive aggression in men.

Resting EEG in alpha and beta bands predicts individual differences in attentional blink magnitude.

Accuracy for a second target (T2) is reduced when it is presented within 500 ms of a first target (T1) in a rapid serial visual presentation (RSVP) - an attentional blink (AB). There are reliable individual differences in the magnitude of the AB. Recent evidence has shown that the attentional approach that an individual typically adopts during a task or in anticipation of a task, as indicated by various measures, predicts individual differences in the AB deficit. It has yet to be observed whether indices of attentional approach when not engaged in a goal-directed task are also relevant to individual differences in the AB. The current studies investigated individual differences in the AB by examining their relationship with attention at rest using quantitative measures of EEG. Greater levels of alpha at rest were associated with larger AB magnitudes, where greater levels of beta at rest were associated with smaller AB magnitudes. Furthermore, individuals with more beta than alpha demonstrated a smaller AB effect than individuals with more alpha than beta. Our results suggest that greater attentional engagement at rest, when not engaged in a goal-directed task, is associated with smaller AB magnitudes.

Event-related potentials during the transition to sleep for individuals with sleep-onset insomnia.

Event-related potentials may be applied to directly measure information-processing deficits associated with the problem of insomnia. This study is a systematic investigation of cortical hyperarousal during the sleep-onset period in participants with sleep-onset insomnia complaints. Thirteen poor sleepers and twelve good sleepers (GS) were administered an oddball task while awake in the morning and evening and during repeated sleep-onset attempts. Participants signaled detection of a higher pitch target tone as they fell asleep. P2 amplitude was significantly smaller for poor sleepers compared to GS, following standard stimuli at all fronto-central sites, in the pre-sleep waking period at sleep onset. Groups did not differ for N1, N350, or P300 in wake, Stage 1, or Stage 2. The smaller P2 indicates that poor sleepers failed to inhibit the irrelevant standard stimuli. This hyper-attentiveness may explain chronic problems with sleep initiation and could be the target of behavioral and pharmaceutical treatment strategies.

Anticipatory attention during the sleep onset period.

To examine whether anticipatory attention or expectancy is a cognitive process that is automatic or requires conscious control, we employed a paired-stimulus event-related potential (ERP) paradigm during the transition to sleep. The slow negative ERP wave observed between two successive stimuli, the Contingent Negative Variation (CNV), reflects attention and expectancy to the second stimulus. Thirteen good sleepers were instructed to respond to the second stimulus in a pair during waking sessions. In a non-response paradigm modified for sleep, participants then fell asleep while tones played. As expected, N1 decreased and P2 increased in amplitude systematically with the loss of consciousness at sleep onset; the CNV was increasingly more positive. Sleep onset latency was correlated with the amplitude of the CNV. The systematic attenuation of the CNV waveform at sleep onset and its absence in sleep indicates that anticipatory attention requires endogenous conscious control.

Benefits of napping in healthy adults: impact of nap length, time of day, age, and experience with napping.

Napping is a cross-cultural phenomenon which occurs across the lifespan. People vary widely in the frequency with which they nap as well as the improvements in alertness and well-being experienced. The systematic study of daytime napping is important to understand the benefits in alertness and performance that may be accrued from napping. This review paper investigates factors that affect the benefits of napping such as duration and temporal placement of the nap. In addition, the influence of subject characteristics such as age and experience with napping is examined. The focus of the review is on benefits for healthy individuals with regular sleep/wake schedules rather than for people with sleep or medical disorders. The goal of the review is to summarize the type of performance improvements that result from napping, critique the existing studies, and make recommendations for future research.

CNS arousal and neurobehavioral performance in a short-term sleep restriction paradigm.

Few studies have investigated waking electrophysiological measures of arousal during sleep restriction. This study examined electroencephalogram (EEG) activity and performance during a 96-hour laboratory protocol where participants slept a baseline night (8 h), were randomly assigned to 3-, 5-, or 8-hour sleep groups for the next two nights sleep restriction (SR1, SR2), and then slept a recovery night (8 h). There were dose-dependent deficits on measures of mood, sleepiness, and reaction time that were apparent during this short-term bout of sleep restriction. The ratio of alpha to theta EEG recorded at rest indicated dose-dependent changes in CNS arousal. At 9:00 hours, both the 3- and 5-hour groups showed EEG slowing (sleepiness) during restriction, with the 3-hour group exhibiting greater deficits. Later in the day at 13:00 hours, the 5-hour group no longer exhibited EEG slowing, but the extent of slowing was more widespread across the scalp for the 3-hour group. High-frequency EEG, a measure of effort, was greater on the mornings following sleep restriction. The 5-hour group had increased beta EEG at central-parietal sites following both nights of restriction, whereas the 3-hour group had increased beta and gamma EEG at occipital regions following the first night only. Short-term sleep restriction leads to deficits in performance as well as EEG slowing that correspond to the amount and duration of sleep loss. High-frequency EEG may be a marker of effort or compensation.

Sensory gating impairments in poor sleepers during presleep wakefulness.

The neurocognitive model of insomnia predicts information processing deficits in poor sleepers. There is some evidence for deficits in later cognitive processing, but earlier sensory processing remains to be investigated. Paired-click stimuli were delivered to good and poor sleepers in a single night. P50 amplitude to stimuli provided an index of sensory gating in presleep wake, rapid eye movement sleep and stage 2 sleep. Poor sleepers exhibited sensory gating impairments during wake. For both groups, gating was intact in rapid eye movement sleep but absent in stage 2 sleep. These data show that poor sleepers experience enhanced sensory processing in the waking period before sleep. Further study is needed to explore sensory gating in chronic primary insomnia, sleep maintenance insomnia, and across multiple recording nights.

Physiological arousal and attention during a week of continuous sleep restriction.

Waking brain physiology underlying deficits from continuous sleep restriction (CSR) is not well understood. Fourteen good sleepers participated in a 21-day protocol where they slept their usual amount in a baseline week, had their time in bed restricted by 33% in a CSR week, and slept the desired amount in a recovery week. Participants slept at home, completing diaries and wearing activity monitors to verify compliance. Each day participants completed an RT task and mood and sleepiness ratings every 3 h. Laboratory assessment of electrophysiology and performance took place at the end of baseline, three times throughout the CSR week, and at the beginning of recovery. Participants reported less sleep during CSR which was confirmed by activity monitors. Correspondingly, well-being and neurobehavioural performance was impaired. Quantitative EEG analysis revealed significantly reduced arousal between the 1st and 7th days of restriction and linear effects at anterior sites (Fp2, Fz, F8, T8). At posterior sites (P4, P8), reductions occurred only later in the week between the 4th and 7th nights of restriction. Both the immediate linear decline in arousal and precipitous drop later in the week were apparent at central sites (C4, Cz). Thus, frontal regions were affected immediately, while parietal regions showed maintenance of function until restriction was more severe. The P300 ERP component showed evidence of reduced attention by the 7th day of restriction (at Pz, P4). EEG and ERPs deficits were more robust in the right-hemisphere, which may reflect greater vulnerability to sleep loss in the non-dominant hemisphere.