Scott Coussens

Sleep Spindle Activity and Cognitive Performance in Healthy Children

STUDY OBJECTIVES To investigate the association between indices of sleep spindle activity and cognitive performance in a sample of healthy children. DESIGN Correlational. Intelligence (Stanford-Binet) and neurocognitive functioning (NEPSY) were assessed, with sleep variables being measured during overnight polysomnography. SETTING Hospital sleep laboratory. PARTICIPANTS Twenty-seven healthy children (mean age 8.19 y; 14 female, 13 male). INTERVENTIONS N/A. MEASUREMENTS AND RESULTS Participants underwent a single night of overnight polysomnography after completing measures of intelligence and neurocognitive functioning. Sleep spindles were visually identified by an experienced sleep scoring technician and separated algorithmically into fast (> 13 Hz) and slow spindle (< 13 Hz) categories. The number of fast spindles was significantly correlated with narrative memory (r(s) = 0.38) and sensorimotor functioning (-0.43). Mean central frequency of spindles was also significantly correlated with sensorimotor functioning (-0.41), planning ability (-0.41), and working memory (-0.54). CONCLUSIONS Basal sleep spindle activity is associated with different aspects of cognitive performance in children. To the extent that these associations in a pediatric population are different from what is known in adult sleep may play an important role in development.

An experimental study of adolescent sleep restriction during a simulated school week: changes in phase, sleep staging, performance and sleepiness

This laboratory study investigated the impact of restricted sleep during a simulated school week on circadian phase, sleep stages and daytime functioning. Changes were examined across and within days and during a simulated weekend recovery. Participants were 12 healthy secondary school students (six male) aged 15–17 years [mean = 16.1 years, standard deviation (SD) = 0.9]. After 2 nights with 10 h (21:30–07:30 hours), time in bed was restricted to 5 h for 5 nights (02:30–07:30 hours), then returned to 10 h time in bed for 2 nights (21:30–07:30 hours). Saliva was collected in dim light on the first and last sleep restriction nights to measure melatonin onset phase. Sleep was recorded polysomnographically, and the Psychomotor Vigilance Task (PVT) and Karolinska Sleepiness Scale were undertaken 3‐hourly while awake. Average phase delay measured by melatonin was 3 h (SD = 50 min). Compared to baseline, sleep during the restriction period contained a smaller percentage of Stages 1 and 2 and rapid eye movement (REM) and a greater percentage of Stage 4. PVT lapses increased significantly during sleep restriction and did not return to baseline levels during recovery. Subjective sleepiness showed a similar pattern during restriction, but returned to baseline levels during recovery. Results suggest that sustained attention in adolescents is affected negatively by sleep restriction, particularly in the early morning, and that a weekend of recovery sleep is insufficient to restore performance. The discrepancy between sleepiness ratings and performance may indicate a lack of perception of this residual impairment.

Resiliency as a mediator of the impact of sleep on child and adolescent behavior

Background Disturbed sleep is detrimental to child behavior; however, the precise means by which this association occurs is unclear. Sleep and resilience can theoretically share an underlying neural mechanism and therefore influence one another. However, the role of resilience in the association between sleep and behavior is not known. The associations between sleep, resilience, and problematic behavior in children and adolescents aged 7–18 years were investigated in this study. Methods A correlational design was used to determine the relationships between total sleep problems, indices of resilience, and internalizing and externalizing behaviors. Results Sleep problems and resiliency variables were strongly correlated, and further, sleep problems were found to be predictive of resiliency scores. Resiliency significantly mediated the relationship between increased sleep problems and both overall internalizing and externalizing behavior problems, and specifically, measures of depression and anxiety. Conclusion Sleep impacted levels of resilience such that greater sleep disturbance reduced resilience and consequently increased problematic behavior, potentially predisposing individuals to psychopathology.

Cognition and objectively measured sleep duration in children: a systematic review and meta-analysis

BACKGROUND Sleep recommendations are widely used to guide communities on childrens sleep needs. Following recent adjustments to guidelines by the National Sleep Foundation and the subsequent consensus statement by the American Academy of Sleep Medicine, we undertook a systematic literature search to evaluate the current evidence regarding relationships between objectively measured sleep duration and cognitive function in children aged 5 to 13 years. METHODS Cognitive function included measures of memory, attention, processing speed, and intelligence in children aged 5 to 13 years. Keyword searches of 7 databases to December 2016 found 23 meeting inclusion criteria from 137 full articles reviewed, 19 of which were suitable for meta-analysis. RESULTS A significant effect (r = .06) was found between sleep duration and cognition, suggesting that longer sleep durations were associated with better cognitive functioning. Analyses of different cognitive domains revealed that full/verbal IQ was significantly associated with sleep loss, but memory, fluid IQ, processing speed and attention were not. Comparison of study sleep durations with current sleep recommendations showed that most children studied had sleep durations that were not within the range of recommended sleep. As such, the true effect of sleep loss on cognitive function may be obscured in these samples, as most children were sleep restricted. CONCLUSIONS Future research using more rigorous experimental methodologies is needed to properly elucidate the relationship between sleep duration and cognition in this age group.

Establishing normal values for pediatric nighttime sleep measured by actigraphy: a systematic review and meta-analysis

Background Despite the widespread use of actigraphy in pediatric sleep studies, there are currently no age-related normative data. Objectives To systematically review the literature, calculate pooled mean estimates of actigraphy-derived pediatric nighttime sleep variables and to examine the magnitude of change with age. Methods A systematic search was performed across eight databases of studies that included at least one actigraphy sleep variable from healthy children aged 0-18 years. Data suitable for meta-analysis were confined to ages 3-18 years with seven actigraphy variables analyzed using random effects meta-analysis and meta-regression performed using age as a covariate. Results In total, 1334 articles did not meet inclusion criteria; 87 had data suitable for review and 79 were suitable for meta-analysis. Pooled mean estimates for overnight sleep duration declined from 9.68 hours (3-5 years age band) to 8.98, 8.85, 8.05, and 7.4 for age bands 6-8, 9-11, 12-14, and 15-18 years, respectively. For continuous data, the best-fit (R2 = 0.74) equation for hours over the 0-18 years age range was 9.02 - 1.04 × [(age/10)^2 - 0.83]. There was a significant curvilinear association between both sleep onset and offset with age (p < .001). Sleep latency was stable at 19.4 min per night. There were significant differences among the older age groups between weekday and weekend/nonschool days (18 studies). Total sleep time in 15-18 years old was 56 min longer, and sleep onset and offset almost 1 and 2 hours later, respectively, on weekend or nonschool days. Conclusion These normative values have potential application to assist the interpretation of actigraphy measures from nighttime recordings across the pediatric age range, and aid future research.

Evidence for spatiotemporally distinct effects of image repetition and perceptual expectations as measured by event-related potentials

ABSTRACT Repeated stimulus presentation leads to reductions in responses of cortical neurons, known as repetition suppression or stimulus‐specific adaptation. Circuit‐based models of repetition suppression provide a framework for investigating patterns of repetition effects that propagate through cortical hierarchies. To further develop such models it is critical to determine whether (and if so, when) repetition effects are modulated by factors such as expectation and attention. We investigated whether repetition effects are influenced by perceptual expectations, and whether the time courses of each effect are similar or distinct, by presenting pairs of repeated and alternating face images and orthogonally manipulating expectations regarding the likelihood of stimulus repetition. Event‐related potentials (ERPs) were recorded from n = 39 healthy adults, to map the spatiotemporal progression of stimulus repetition and stimulus expectation effects, and interactions between these, using mass univariate analyses. We also tested for another expectation effect that may contribute to repetition effects in many previous experiments: that repeated stimulus identities are predictable after seeing the first stimulus in a trial, but unrepeated stimulus identities cannot be predicted. Separate blocks were presented with predictable and unpredictable alternating face identities. Multiple repetition and expectation effects were identified between 99 and 800ms from stimulus onset, which did not statistically interact at any point and exhibited distinct spatiotemporal patterns of effects. Repetition effects in blocks with predictable alternating faces were smaller than in unpredictable alternating face blocks between 117‐179 ms and 506–652ms, and larger between 246 and 428ms. The distinct spatiotemporal patterns of repetition and expectation effects support separable mechanisms underlying these phenomena. However, previous studies of repetition effects, in which the repeated (but not unrepeated) stimulus was predictable, are likely to have conflated repetition and stimulus predictability effects. HighlightsERP face image repetition effects were apparent between 99 and 800ms from stimulus onset.Expectations of stimulus image properties did not modulate face repetition effects.The predictability of unrepeated stimuli influenced repetition effect magnitudes.

Perceptual Expectations Do Not Modulate Image Repetition Effects As Measured By Event-Related Potentials

Repeated stimulus presentation leads to complex changes in cortical neuron response properties, commonly known as repetition suppression or stimulus-specific adaptation. Circuit-based models of repetition suppression provide a framework for investigating patterns of repetition effects that propagate through cortical hierarchies. To further develop such models it is critical to determine whether (and if so, when) repetition effects are modulated by top-down influences, such as those related to perceptual expectation. We investigated this by presenting pairs of repeated and alternating face images, and orthogonally manipulating expectations regarding the likelihood of stimulus repetition. Event-related potentials (ERPs) were recorded from n=39 healthy adults, to map the spatiotemporal progression of stimulus repetition and expectation effects, and interactions between these factors, using mass univariate analyses. We also tested whether the ability to predict unrepeated (compared to repeated) face identities could influence the magnitude of observed repetition effects, by presenting separate blocks with predictable and unpredictable alternating faces. Multiple repetition and expectation effects were identified between 99-800ms from stimulus onset, which did not statistically interact at any point. Repetition effects in blocks with predictable alternating faces were smaller than in unpredictable alternating face blocks between 117-179ms and 506-652ms, and larger between 246-428ms. ERP repetition effects appear not to be modulated by perceptual expectations, supporting separate mechanisms for repetition and expectation suppression. However, previous studies that aimed to test for repetition effects, in which the repeated (but not unrepeated) stimulus was predictable, are likely to have conflated repetition and stimulus predictability effects. Highlights - ERP face image repetition effects were apparent between 99-800ms from stimulus onset - Expectations of stimulus image properties did not modulate face repetition effects - The predictability of unrepeated stimuli influenced repetition effect magnitudes

Temporal expectations modulate face image repetition suppression as indexed by event-related potentials

Repeated exposure to a stimulus leads to reduced responses of stimulus-selective sensory neurons, an effect known as repetition suppression or stimulus-specific adaptation. Several influential models have been proposed to explain repetition suppression within hierarchically-organised sensory systems, with each specifying different mechanisms underlying repetition effects. We manipulated temporal expectations within a face repetition experiment to test a critical prediction of the predictive coding model of repetition suppression: that repetition effects will be larger following stimuli that appear at expected times compared to stimuli that appear at unexpected times. We recorded event-related potentials from 18 participants and mapped the spatiotemporal progression of repetition effects using mass univariate analyses. We then assessed whether the magnitudes of observed face image repetition effects were influenced by temporal expectations. In each trial participants saw an adapter face, followed by a 500ms or 1000ms interstimulus interval (ISI), and then a test face, which was the same or a different face identity to the adapter. Participants’ expectations for whether the test face would appear after a 500ms ISI were cued by the sex of the adapter face. Our analyses revealed multiple repetition effects with distinct scalp topographies, extending until at least 800ms from stimulus onset. An early (158-203ms) repetition effect was larger for stimuli following surprising, rather than expected, 500ms ISI durations, contrary to the model predictions of the predictive coding model of repetition suppression. Later (230-609ms) repetition effects tended to be larger following expected stimulus onset times, in line with predictive coding models. Our results indicate that the relationship between repetition suppression and temporal expectation differs across the time course of the stimulus-evoked response, suggesting multiple distinct mechanisms driving repetition suppression that operate at different latencies within the visual hierarchy. Highlights - Multiple face image repetition effects identified from 162-800ms post stimulus onset - Temporal expectations influenced the magnitudes of repetition effects - Temporal expectation effects differed for early and late stimulus-evoked responses

Alpha Oscillations Prior to Encoding Preferentially Modulate Memory Consolidation during Wake Relative to Sleep

Sleep promotes memory consolidation through unique neuromodulatory activity. However, little is known about the impact of attention during pre-sleep memory encoding on later memory performance. The current study aimed to address the question of whether attentional state prior to encoding, as indexed by alpha oscillatory activity, modulates the consolidation of images across periods of sleep and wake. 22 participants aged 18 – 41 years (mean age = 27.3) viewed 120 emotionally valenced images (positive, negative, neutral) before a 2hr afternoon sleep opportunity and an equivalent period of wake. Following the sleep and wake conditions, participants were required to distinguish between 120 previously seen (target) images and 120 new (distractor) images. Relative alpha power – adjusted according to participants’ individual alpha frequency — was computed to index attentional state prior to the learning phase. Generalised linear mixed effects modelling revealed memory performance was modulated by attention, such that greater pre-encoding alpha synchronisation promoted memory consolidation after wake, but not sleep. There was no difference in memory performance between positive, negative and neutral stimuli. Modulations in alpha oscillatory activity may help coordinate the flow of information between task-relevant cortical regions and a thalamo-cortical loop that subserves the formation of memory during times of wake but not sleep.

T-O-136 THE EFFECTS OF A HIGH SUGAR DIET ON SLEEP QUALITY AND ATTENTIONAL CAPACITY IN PREPUBESCENT GIRLS: A PRELIMINARY STUDY

Results: The overall fibromyalgia sample (N=2196) had a mean age of 53.32 (SD=12.63). Patients experiencing severe or general sleep difficulties were significantly more likely to be on disability (severe=28.01% vs. general=23.17% vs. none=14.87%; p<0.05) and less likely to possess insurance coverage (87.09% vs. 90.07% vs. 93.68%; p<0.05) compared with patients without sleep difficulties. After adjustment for demographic and health characteristics, patients experiencing severe or general sleep difficulties reported higher mean direct costs (