Font disfluency and reading performance in children: An event-related potential study.

Expert adult readers process fluent and disfluent fonts differently, at both early perceptual and late higher-order processing stages. This finding has been interpreted as reflecting the more difficult to read disfluent fonts requiring greater neural resources. We aimed to investigate whether neural activity is affected by font disfluency in pre-adolescent readers, and to determine if neural responses are related to reading performance. Thirty-three participants between 8 and 12 years old completed two one-back tasks using letter and word stimuli, where font was manipulated (fluent versus disfluent stimuli), during which electroencephalography was recorded. Event related potentials (ERPs) were calculated relative to non-target stimuli for both tasks. The Woodcock Johnson III Tests of Achievement reading specific tests, and the Castles and Coltheart Test 2 were also collected. Font (fluent versus disfluent stimuli) did not consistently affect neural activity during both the letter and word tasks. Fluent stimuli elicited greater late activity (450-600 ms) than disfluent stimuli during the word task, suggesting easy-to-read fonts may enhance the maintenance of words in visual working memory and facilitate the retrieval of semantic information. However, reading performance was not associated with neural disfluency effects, suggesting that pre-adolescents are still at an early developmental reading period. Font manipulation may be a useful way to track developmental reading trajectories in the brain.

Neural indices of associative learning in pre-adolescents: An event-related potential study.

This study investigated electroencephalography (EEG) correlates of prediction error during probabilistic learning in pre-adolescents. The detection of prediction errors, the discrepancies between experienced and anticipated outcomes, is thought to be a critical mechanism that drives new learning. Thirty-three typically developing pre-adolescents (mean age = 10.62 years) participated in an associative learning task in which they learned the probabilistic relationships between cues and outcome stimuli in the absence of explicit feedback. We investigated whether three outcome-locked event-related potentials (ERPs) could reflect prediction error processing: the P3, the late positive potential (LPP), and the feedback-related negativity (FRN). All ERP components investigated were sensitive to the magnitude of hypothetical prediction errors that were estimated based on each individual's learning performance. Higher estimated prediction errors generated larger P3 and LPP components, and a more negative FRN. These findings indicate that pre-adolescents are capable of undergoing probabilistic learning in the absence of explicit feedback, much in the same way as adults, and that prediction error processing is physiologically indexed via the FRN, P3 and LPP following outcome stimuli.

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

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.

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.

Investigating letter recognition in the brain by varying typeface: an event-related potential study.

We aimed to investigate the contributions of visual letter form and abstract letter identity to the time course of letter recognition, by manipulating the typeface (i.e. font) in which letters were presented. Twenty-six adult participants completed a modified one-back task, where letters where presented in easy-to-read typefaces ("fluent" letter stimuli) or difficult-to-read typefaces ("disfluent" letter stimuli). Task instructions necessitated that participant's focus on letter identity not visual letter form. Electroencephalography was collected and event-related potentials (ERPs) were calculated relative to letter stimuli. It was found that typeface affected both early-mid (N1 amplitude and P2-N2 amplitude and latency) and late processing (450-600ms), thereby including time points whereby it is theorised that abstract identity is extracted from visual letter form (that is, 300ms post-stimulus). Visual features of the letter therefore affect its processing well beyond the currently theorised point at which abstract information is extracted; which could be explained by a feedback loop between abstract letter representations and lower-level visual form processing units, which is not included in current cognitive reading models.

Investigating self-report and neuropsychological assessments of cognitive flexibility in people with and without persistent pain: An online, cross-sectional, observational study.

Introduction: People with persistent pain experience problems modifying their cognition and behaviours when task or environmental demands change - abilities otherwise known as cognitive flexibility. However, limitations and inconsistent results of previous studies raise concerns over the quality of that evidence. We aimed to determine whether people with and without persistent pain differ on two assessments that are commonly used to assess cognitive flexibility. We also examined the relationship between the two assessments and explored whether people with and without persistent pain are distinguishable based on their scores on these assessments. Methods: Participant demographics and symptoms of anxiety and depression were assessed. Participants completed the Cognitive Flexibility Inventory (CFI) and the Wisconsin Card Sorting Test (WCST). Multiple linear regression on the two outcome variables: CFI (total score) and WCST (% perseverative responses) was applied using backward stepwise selection. Both outcomes were calculated as a standardised proportion of the outcome scale and log-odds transformed to meet the model assumptions. Correlation analysis and logistic regression were used to investigate our secondary and exploratory aims. Results: Data were available from 128 participants with persistent pain and 68 pain-free controls. After adjusting for covariates, no differences were found between people with and without persistent pain on either assessment of cognitive flexibility. No significant correlations were detected between the two assessments in either group. The probability of having persistent pain was also not associated with scores on either or both assessments. Conclusion: 'Cognitive flexibility' appears similar in people with and without persistent pain.

The effect of age-related macular degeneration on cognitive test performance.

The reliable assessment of cognitive functioning is critical to the study of brain-behaviour relationships. Yet conditions that are synchronous which ageing, including visual decline, are easily overlooked when interpreting cognitive test scores. The purpose of this study was to demonstrate the negative consequences of visual impairments on cognitive tests performance. Moderate to severe levels of age-related macular degeneration were simulated, with a set of goggles, in a sample of twenty-four normally sighted participants while they completed two cognitive tasks: a vision-dependent reaction time task and a vision-independent verbal fluency test. Performance on the reaction time task significantly decreased (p < 0.001) in the simulated age-related macular degeneration condition, by as much as 25 percentile ranks. In contrast, performance on the verbal fluency test were not statistically different between the simulated and normal vision conditions (p = 0.78). The findings highlight the importance of considering visual functioning when assessing cognitive function. When vision is not accounted for, low test scores may inaccurately indicate poor cognition. Such false attributions may have significant ramification for diagnosis and research on cognitive functioning.

The psychological impact of instrumental activities of daily living on people with simulated age-related macular degeneration.

BACKGROUND: People with age-related macular degeneration (AMD) can report reduced mental health. There is also evidence that they struggle with daily tasks because of vision loss. AIMS: The purpose of this study was to assess the psychological impact of instrumental activities of daily living on people with simulated AMD. METHOD: Twenty-four normally sighted participants completed 12 household tasks, in a simulated home environment, under a moderate-to-severe AMD simulation. Participants' psychological state was measured through self-report questionnaires and physiological measurements related to anxiety and stress. Tasks were completed twice, under counterbalanced vision conditions (normal and simulated AMD). RESULTS: Linear mixed models on vision condition (normal versus simulated AMD) and trial order (trial 1 versus trial 2) revealed a significant large negative effect of the AMD simulation on time to complete tasks, and the anxiety, task engagement and distress self-reports (all P < 0.024, all ω2 > 0.177). There were also significant medium-large effects of trial order on time, task incompletion, task errors, and the anxiety and task engagement self-reports (all P < 0.047, all ω2 > 0.130), whereby the results improved during the second attempt at the tasks. No physiological measures were significant (all P > 0.05). CONCLUSIONS: Completing instrumental activities of daily living under an AMD simulation had a negative impact on participants' self-reported mental state. The observed trial order effects also illuminated how practice with tasks could ease anxiety and stress over time.

Homeostatic response to sleep restriction in adolescents.

The high prevalence of chronic sleep restriction in adolescents underscores the importance of understanding how adolescent sleep is regulated under such conditions. One component of sleep regulation is a homeostatic process: if sleep is restricted, then sleep intensity increases. Our knowledge of this process is primarily informed by total sleep deprivation studies and has been incorporated in mathematical models of human sleep regulation. Several animal studies, however, suggest that adaptation occurs in chronic sleep restriction conditions, showing an attenuated or even decreased homeostatic response. We investigated the homeostatic response of adolescents to different sleep opportunities. Thirty-four participants were allocated to one of three groups with 5, 7.5, or 10 h of sleep opportunity per night for five nights. Each group underwent a protocol of nine nights designed to mimic a school week between two weekends: two baseline nights (10 h sleep opportunity), five condition nights (5, 7.5, or 10 h), and two recovery nights (10 h). Measures of sleep homeostasis (slow-wave activity and slow-wave energy) were calculated from frontal and central EEG derivations and compared to predictions derived from simulations of the homeostatic process of the two-process model of sleep regulation. Only minor differences were found between empirical data and model predictions, indicating that sleep homeostasis is preserved under chronic sleep restriction in adolescents. These findings improve our understanding of effects of repetitive short sleep in adolescents.

Investigating how electroencephalogram measures associate with delirium: A systematic review.

Delirium is a common neurocognitive disorder in hospital settings, characterised by fluctuating impairments in attention and arousal following an acute precipitant. Electroencephalography (EEG) is a useful method to understand delirium pathophysiology. We performed a systematic review to investigate associations between delirium and EEG measures recorded prior, during, and after delirium. A total of 1,655 articles were identified using PsycINFO, Embase and MEDLINE, 31 of which satisfied inclusion criteria. Methodological quality assessment was undertaken, resulting in a mean quality score of 4 out of a maximum of 5. Qualitative synthesis revealed EEG slowing and reduced functional connectivity discriminated between those with and without delirium (i.e. EEG during delirium); the opposite pattern was apparent in children, with cortical hyperexcitability. EEG appears to have utility in differentiating those with and without delirium, but delirium vulnerability and the long-term effects on brain function require further investigation. Findings provide empirical support for the theory that delirium is a disorder of reduced functional brain integration.

EEG and behavioral correlates of attentional processing while walking and navigating naturalistic environments.

The capacity to regulate one's attention in accordance with fluctuating task demands and environmental contexts is an essential feature of adaptive behavior. Although the electrophysiological correlates of attentional processing have been extensively studied in the laboratory, relatively little is known about the way they unfold under more variable, ecologically-valid conditions. Accordingly, this study employed a 'real-world' EEG design to investigate how attentional processing varies under increasing cognitive, motor, and environmental demands. Forty-four participants were exposed to an auditory oddball task while (1) sitting in a quiet room inside the lab, (2) walking around a sports field, and (3) wayfinding across a university campus. In each condition, participants were instructed to either count or ignore oddball stimuli. While behavioral performance was similar across the lab and field conditions, oddball count accuracy was significantly reduced in the campus condition. Moreover, event-related potential components (mismatch negativity and P3) elicited in both 'real-world' settings differed significantly from those obtained under laboratory conditions. These findings demonstrate the impact of environmental factors on attentional processing during simultaneously-performed motor and cognitive tasks, highlighting the value of incorporating dynamic and unpredictable contexts within naturalistic designs.

DelIrium VULnerability in GEriatrics (DIVULGE) study: a protocol for a prospective observational study of electroencephalogram associations with incident postoperative delirium.

INTRODUCTION: Delirium is a neurocognitive disorder common in older adults in acute care settings. Those who develop delirium are at an increased risk of dementia, cognitive decline and death. Electroencephalography (EEG) during delirium in older adults is characterised by slowing and reduced functional connectivity, but markers of vulnerability are poorly described. We aim to identify EEG spectral power and event-related potential (ERP) markers of incident delirium in older adults to understand neural mechanisms of delirium vulnerability. Characterising delirium vulnerability will provide substantial theoretical advances and outcomes have the potential to be translated into delirium risk assessment tools. METHODS AND ANALYSIS: We will record EEG in 90 participants over 65 years of age prior to elective coronary artery bypass grafting (CABG) or transcatheter aortic valve implantation (TAVI). We will record 4-minutes of resting state (eyes open and eyes closed) and a 5-minute frequency auditory oddball paradigm. Outcome measures will include frequency band power, 1/f offset and slope, and ERP amplitude measures. Participants will undergo cognitive and EEG testing before their elective procedures and daily postoperative delirium assessments. Group allocation will be done retrospectively by linking preoperative EEG data according to postoperative delirium status (presence, severity, duration and subtype). ETHICS AND DISSEMINATION: This study is approved by the Human Research Ethics Committee of the Royal Adelaide Hospital, Central Adelaide Local Health Network and the University of South Australia Human Ethics Committee. Findings will be disseminated through peer-reviewed journal articles and presentations at national and international conferences. TRIAL REGISTRATION NUMBER: ACTRN12618001114235 and ACTRN12618000799257.

A pilot study investigating the impact of a caffeine-nap on alertness during a simulated night shift.

Consuming coffee immediately prior to a nap, known as a caffeine-nap, has been shown to improve alertness during the day, but it is unknown whether a caffeine-nap is effective at reducing sleep inertia during the night. A simulated shiftwork cross-over laboratory study was conducted whereby participants (N = 6, 4 F, 21-36y) consumed 200 mg of caffeine, or decaffeinated coffee (placebo), immediately prior to a 30 min nap opportunity at 03:30 h. Compared to placebo, the caffeine-nap resulted in improved vigilant attention and subjective fatigue in the 45 min post-nap opportunity. The caffeine-nap may be useful in reducing sleep inertia in shift workers who nap on nightshift.

Acute aerobic exercise and neuroplasticity of the motor cortex: A systematic review.

OBJECTIVES: To synthesise the existing literature investigating if acute aerobic exercise enhances the response to experimentally-induced neuroplasticity paradigms. METHODS: A systematic search of electronic databases Medline, PsycInfo and Embase was undertaken on 26 April 2018 and updated on 17 May 2019. Studies were included if they involved a bout of aerobic exercise; prescribed a bout of rest as a control condition; utilized a non-invasive brain stimulation paradigm to induce neuroplasticity; used TMS to assess neuroplasticity outcomes; participants were healthy 18-65year old males and females with no diagnosed neurological/psychological impairments. RESULTS: Eight papers (containing 12 experiments) met inclusion criteria. All studies utilized cycling or treadmill exercise as their exercise modality, and exercise intensity ranged from low intensity continuous exercise to high-intensity interval exercise. Four neuroplasticity paradigms were employed including paired associative stimulation (PAS) (n=3), continuous theta-burst stimulation (cTBS) (n=2), intermittent theta-burst stimulation (iTBS) (n=2) and transcranial direct current stimulation (n=1). Aerobic exercise enhanced neuroplastic responses (compared to rest) in seven of the 12 experiments. CONCLUSIONS: This review provides emerging evidence that acute aerobic exercise can enhance the response to experimentally-induced neuroplasticity paradigms. However, there remains great variability in the study design and reporting of effects in these studies and thus a more standardized approach is encouraged to better understand the relationship between acute aerobic exercise and neuroplasticity. Future studies should consider optimizing intensity, paradigms and duration of both exercise and neuroplasticity paradigms employed.

Individual alpha frequency modulates sleep-related emotional memory consolidation.

Alpha-band oscillatory activity is involved in modulating memory and attention. However, few studies have investigated individual differences in oscillatory activity during the encoding of emotional memory, particularly in sleep paradigms where sleep is thought to play an active role in memory consolidation. The current study aimed to address the question of whether individual alpha frequency (IAF) modulates the consolidation of declarative memory across periods of sleep and wake. 22 participants aged 18-41 years (mean age = 25.77) viewed 120 emotionally valenced images (positive, negative, neutral) and completed a baseline memory task 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 learned (target) images and 120 new (distractor) images. This method allowed us to delineate the role of different oscillatory components of sleep and wake states in the emotional modulation of memory. Linear mixed-effects models revealed interactions between IAF, rapid eye movement sleep theta power, and slow-wave sleep slow oscillatory density on memory outcomes. These results highlight the importance of individual factors in the EEG in modulating oscillatory-related memory consolidation and subsequent behavioural outcomes and test predictions proposed by models of sleep-based memory consolidation.

Increasing Objective Cardiometabolic Burden Associated With Attenuations in the P3b Event-Related Potential Component in Older Adults.

Cardiometabolic diseases and risk factors increase the risk of late-life cognitive impairment and dementia and have also been associated with detrimental gray and white matter changes. However, the functional brain changes associated with cardiometabolic health in late-life are unclear. We sought to characterize these functional changes by recording event-related potentials (ERPs) during an n-back working memory task (0, 1, and 2 back) in 85 adults (60% female) between 50 and 80 years of age. Due to a stratified recruitment approach, participants varied widely in relation to cognitive function and cardiometabolic health. Standard and objective cut-offs for high blood glucose, waist to hip ratio (i.e., obesity), high blood cholesterol, and hypertension were employed to generate a summative score for cardiometabolic burden (none, one, or two or more above cut-off). Mixed effects modeling (covarying for age and gender) revealed no statistically significant associations between cardiometabolic burden and visual P1 and N1 component amplitudes. There was a significant effect for the P3b component: as cardiometabolic burden increased, P3b amplitude decreased. We show that cardiometabolic factors related to the development of cognitive impairment and dementia in late-life associate with brain activity, as recorded via ERPs. Findings have relevance for the monitoring of lifestyle interventions (typically targeting cardiometabolic factors) in aging, as ERPs may provide a more sensitive measure of change than cognitive performance. Further, our results raise questions related to the findings of a broad range of ERP studies where the groups compared may differ in their cardiometabolic health status (not only in psychological symptomatology).

Temporal expectations modulate face image repetition suppression of early stimulus evoked 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 500 ms or 1000 ms 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 500 ms ISI were cued by the sex of the adapter face. Our analyses revealed multiple repetition effects with distinct scalp topographies, extending until at least 800 ms from stimulus onset. An early (158-203 ms) repetition effect was larger for stimuli following surprising, rather than expected, 500 ms ISI durations, contrary to the model predictions of the predictive coding model of repetition suppression. During this time window temporal expectation effects were larger for alternating, compared to repeated, test stimuli. Statistically significant temporal expectation by stimulus repetition interactions were not found for later (230-609 ms) time windows. Our results provide further evidence that repetition suppression can reduce neural effects of expectation and surprise, indicating that there are multiple interactive mechanisms supporting sensory predictions within the visual hierarchy.

Sleep spindles in adolescence: a comparison across sleep restriction and sleep extension.

BACKGROUND: The tendency for adolescents to have restricted sleep has been examined in numerous studies; however, the impact of sleep restriction on adolescents' neural activity during sleep (measured by electroencephalography (EEG)) is less extensively researched, particularly regarding sleep spindles. METHODS: In this experimental study, 34 adolescents attended a 10-day laboratory study where they received five consecutive nights of either 5 h, 7.5 h or 10 h of sleep opportunity, with one adaptation, one baseline and two recovery nights of 10 h of sleep opportunity before and after the experimental phase. RESULTS: Both within- and between-subjects effects were observed for fast sleep spindle characteristics of density, duration and amplitude. Overall, when experiencing severe sleep restriction, fast spindles in adolescents were lower in amplitude and longer in duration. Sex differences were also seen for fast spindle amplitude. CONCLUSIONS: This investigation adds to the knowledge in this field by investigating specific sleep spindle characteristics in the context of experimentally manipulated sleep. Sleep restriction is highly prevalent among adolescents. These findings indicate that chronic sleep restriction has an impact on brain activity related to sleep spindles.

Estimating adolescent sleep need using dose-response modeling.

Study Objectives: This study will (1) estimate the nightly sleep need of human adolescents, (2) determine the time course and severity of sleep-related deficits when sleep is reduced below this optimal quantity, and (3) determine whether sleep restriction perturbs the circadian system as well as the sleep homeostat. Methods: Thirty-four adolescents aged 15 to 17 years spent 10 days and nine nights in the sleep laboratory. Between two baseline nights and two recovery nights with 10 hours' time in bed (TIB) per night, participants experienced either severe sleep restriction (5-hour TIB), moderate sleep restriction (7.5-hour TIB), or no sleep restriction (10-hour TIB) for five nights. A 10-minute psychomotor vigilance task (PVT; lapse = response after 500 ms) and the Karolinska Sleepiness Scale were administered every 3 hours during wake. Salivary dim-light melatonin onset was calculated at baseline and after four nights of each sleep dose to estimate circadian phase. Results: Dose-dependent deficits to sleep duration, circadian phase timing, lapses of attention, and subjective sleepiness occurred. Less TIB resulted in less sleep, more lapses of attention, greater subjective sleepiness, and larger circadian phase delays. Sleep need estimated from 10-hour TIB sleep opportunities was approximately 9 hours, while modeling PVT lapse data suggested that 9.35 hours of sleep is needed to maintain optimal sustained attention performance. Conclusions: Sleep restriction perturbs homeostatic and circadian systems, leading to dose-dependent deficits to sustained attention and sleepiness. Adolescents require more sleep for optimal functioning than typically obtained.

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

BACKGROUND: Sleep recommendations are widely used to guide communities on children's 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.