Oscillatory and Aperiodic Neural Activity Jointly Predict Language Learning.

Memory formation involves the synchronous firing of neurons in task-relevant networks, with recent models postulating that a decrease in low-frequency oscillatory activity underlies successful memory encoding and retrieval. However, to date, this relationship has been investigated primarily with face and image stimuli; considerably less is known about the oscillatory correlates of complex rule learning, as in language. Furthermore, recent work has shown that nonoscillatory (1/ƒ) activity is functionally relevant to cognition, yet its interaction with oscillatory activity during complex rule learning remains unknown. Using spectral decomposition and power-law exponent estimation of human EEG data (17 women, 18 men), we show for the first time that 1/ƒ and oscillatory activity jointly influence the learning of word order rules of a miniature artificial language system. Flexible word-order rules were associated with a steeper 1/ƒ slope, whereas fixed word-order rules were associated with a shallower slope. We also show that increased theta and alpha power predicts fixed relative to flexible word-order rule learning and behavioral performance. Together, these results suggest that 1/ƒ activity plays an important role in higher-order cognition, including language processing, and that grammar learning is modulated by different word-order permutations, which manifest in distinct oscillatory profiles.

Consolidation and generalisation across sleep depend on individual EEG factors and sleep spindle density.

Sleep is involved in both the consolidation of discrete episodes, as well as the generalisation of acquired memories into schemata. Here, we have isolated early versus late periods of sleep in order to replicate previous behavioural findings and to demonstrate: i) that distinct sleep and sleep electroencephalography (EEG) factors influence the generalisation of learned information, and; ii) that the consolidation and generalisation of memory across sleep depends on individual alpha frequency (IAF) and strength of initial encoding. Subjects underwent a night-half protocol with polysomnography (PSG), and completed a Chinese character-English paired associates learning task. Recognition accuracy of learned word-pairs, the extent to which the subject was able to generalise this knowledge, and the extent of explicit transfer of knowledge were measured. Results demonstrate that quality of initial learning determined the relationship between sleep neurophysiology and outcome, with IAF modulating this effect. We also note an effect of IAF in modulating the effect of sleep spindles in determining generalisation of learned materials. Finally, we note a complex relationship between initial learning, IAF and sleep spindle density in determining when information will reach explicit awareness across sleep. Together, these data implicate encoding factors in subsequent offline processing, demonstrate a potential role for individual differences in the EEG and subsequently add to our understanding of the the conditions in which sleep may benefit both memory and learning.

A Systematic Review of Cognitive Functioning After Traumatic Brain Injury in Individuals Aged 10-30 Years.

Given the importance of the period of life from 10 to 30 years in terms of cognitive development and education, combined with the high incidence of traumatic brain injury (TBI) during this period, and limited consensus as to the pattern and degree of cognitive impairment post TBI during this period, we conducted a systematic review to investigate cognitive performance across a range of domains among individuals between the ages of 10 and 30 years who had sustained a TBI. We searched five databases and identified 799 unique records; 52 met our inclusion criteria. These studies reported cognitive function for intelligence, attention, memory, processing speed, and executive function. The majority of the studies reported significant effects, suggesting that TBI is associated with cognitive impairments in these domains. Nine of the studies used physiological tests (EEG and fMRI), the outcomes of which supported behaviorally demonstrated cognitive deficits. In the studies we reviewed, individuals aged 10-30 years who had experienced a TBI performed worse than healthy controls on cognitive function measures-specifically for attention, memory, processing speed, and executive function. In the studies that subjected the individuals with TBI to EEG and fMRI, atypical activation in associated brain regions was demonstrated while the individuals were undergoing cognitive tasks. However, caution should be taken when interpreting the overall results due to the high risk of bias across the majority of the studies. The broader implications of reduced cognitive performance after TBI across this age range are yet to be fully understood.

What Box: A task for assessing language lateralization in young children.

The assessment of active language lateralization in infants and toddlers is challenging. It requires an imaging tool that is unintimidating, quick to setup, and robust to movement, in addition to an engaging and cognitively simple language processing task. Functional Transcranial Doppler Ultrasound (fTCD) offers a suitable technique and here we report on a suitable method to elicit active language production in young children. The 34-second "What Box" trial presents an animated face "searching" for an object. The face "finds" a box that opens to reveal a to-be-labelled object. In a sample of 95 children (1 to 5 years of age), 81% completed the task-32% with ≥10 trials. The task was validated (ρ = 0.4) against the gold standard Word Generation task in a group of older adults (n = 65, 60-85 years of age), though was less likely to categorize lateralization as left or right, indicative of greater measurement variability. Existing methods for active language production have been used with 2-year-old children while passive listening has been conducted with sleeping 6-month-olds. This is the first active method to be successfully employed with infants through to pre-schoolers, forming a useful tool for populations in which complex instructions are problematic.

The effects of sleep restriction and sleep deprivation in producing false memories.

False memory has been claimed to be the result of an associative process of generalisation, as well as to be representative of memory errors. These can occur at any stage of memory encoding, consolidation, or retrieval, albeit through varied mechanisms. The aim of this paper is to experimentally determine: (i) if cognitive dysfunction brought about by sleep loss at the time of stimulus encoding can influence false memory production; and (ii) whether this relationship holds across sensory modalities. Subjects undertook both the Deese-Roedigger-McDermott (DRM) false memory task and a visual task designed to produce false memories. Performance was measured while subjects were well-rested (9h Time in Bed or TIB), and then again when subjects were either sleep restricted (4h TIB for 4 nights) or sleep deprived (30h total SD). Results indicate (1) that partial and total sleep loss produced equivalent effects in terms of false and veridical verbal memory, (2) that subjects performed worse after sleep loss (regardless of whether this was partial or total sleep loss) on cued recognition-based false and veridical verbal memory tasks, and that sleep loss interfered with subjects' ability to recall veridical, but not false memories under free recall conditions, and (3) that there were no effects of sleep loss on a visual false memory task. This is argued to represent the dysfunction and slow repair of an online verbal associative process in the brain following inadequate sleep.

Parent versus teacher report of daytime behavior in snoring children.

PURPOSE: Problematic behavior is widely reported in children with sleep-disordered breathing (SDB). Daytime behavior is an important component in the evaluation of clinical history in SDB; however, there is a reliance on parental report alone, and it is unclear whether reports by teachers will aid diagnosis. METHODS: We assessed sleep and behavior reported by both parents and teachers in 19 children with SDB and 27 non-snoring controls. All children were screened for prior diagnoses of other medical and/or behavior and learning disorders and underwent polysomnography and both parental and teacher assessment of behavior. RESULTS: Both parents and teachers report greater problematic behavior in SDB children, predominantly of an internalizing nature. Despite this consistency and moderate correlation between informants, the agreement between parent and teacher reports of individual child behavior was poor when assessed using Bland-Altman plots. CONCLUSIONS: Clinicians should be mindful that the behavioral history of a child being evaluated for SDB may vary depending on whether parent or teacher report is being discussed as this may influence clinical decision making.

Instantaneous effects of mindfulness meditation on tennis return performance in elite junior athletes completing an implicitly sequenced serve return task.

Single-session meditation augmentation of sport-specific skill performance was tested with elite junior tennis athletes. Athletes completed one of two styles of mindfulness meditation (focused-attention or open-monitoring) or a control listening condition prior to performing an implicitly sequenced tennis serve return task involving the goal of hitting a target area placed on the service court. Unbeknownst to athletes, six distinct serves followed a repeating second-order conditional sequence for two task blocks before the sequence was altered in a third transfer block. Task performance was operationalized as serve return outcome and analyzed using beta regression modeling. Models analyzed group by block differences in the proportion of returned serves (i.e., non-aces), returns placed in the service court, and target hits. Contrary to previous laboratory findings, results did not support meditation-related augmentation of performance and/or sequence learning. In fact, compared to control, meditation may have impaired performance improvements and acquisition of serve sequence information. It is possible that the effects of single-session meditation seen in laboratory research may not extend to more complex motor tasks, at least in highly-trained adolescents completing a well-learned skill. Further research is required to elucidate the participant, task, and meditation-related characteristics that might promote single-session meditation performance enhancement.

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.

Is there a clear link between overweight/obesity and sleep disordered breathing in children?

The proportion of children who are overweight or obese has risen steadily in recent decades and approaches a quarter of all children in Western countries. This global epidemic of excess weight and adiposity in humans is associated with increased morbidity and mortality, especially related to diabetes and poor cardiovascular health. It would appear that obesity is also generally accepted to be an important risk factor in the development of sleep disordered breathing (SDB), in children as well as adults. The article, "The prevalence, anatomical correlates and treatment of sleep-disordered breathing in obese children and adolescents", by Verhulst et al., also in this issue, reviews evidence supporting the view that obese children are at higher risk of developing SDB. We believe, however, that the available studies do not support a straightforward association of overweight or obesity with increased prevalence of SDB. Rather, the available data is clearly equivocal mainly due to methodological differences between the previous studies. This review nonetheless examines the factors which may modulate the relationship between overweight or obesity and prevalence of SDB, particularly ethnicity and age.

Sleep-Dependent Memory Consolidation and Incremental Sentence Comprehension: Computational Dependencies during Language Learning as Revealed by Neuronal Oscillations.

We hypothesize a beneficial influence of sleep on the consolidation of the combinatorial mechanisms underlying incremental sentence comprehension. These predictions are grounded in recent work examining the effect of sleep on the consolidation of linguistic information, which demonstrate that sleep-dependent neurophysiological activity consolidates the meaning of novel words and simple grammatical rules. However, the sleep-dependent consolidation of sentence-level combinatorics has not been studied to date. Here, we propose that dissociable aspects of sleep neurophysiology consolidate two different types of combinatory mechanisms in human language: sequence-based (order-sensitive) and dependency-based (order-insensitive) combinatorics. The distinction between the two types of combinatorics is motivated both by cross-linguistic considerations and the neurobiological underpinnings of human language. Unifying this perspective with principles of sleep-dependent memory consolidation, we posit that a function of sleep is to optimize the consolidation of sequence-based knowledge (the when) and the establishment of semantic schemas of unordered items (the what) that underpin cross-linguistic variations in sentence comprehension. This hypothesis builds on the proposal that sleep is involved in the construction of predictive codes, a unified principle of brain function that supports incremental sentence comprehension. Finally, we discuss neurophysiological measures (EEG/MEG) that could be used to test these claims, such as the quantification of neuronal oscillations, which reflect basic mechanisms of information processing in the brain.

The Relationship Between Caffeine, Sleep, and Behavior in Children.

STUDY OBJECTIVES: To examine caffeine consumption from various dietary sources in a cohort of Australian children and the relationship between caffeine consumption, sleep, and daytime behavior. METHODS: Children aged 8 to 12 years and their parents/guardians completed a battery of questionnaires. Children completed a caffeine questionnaire while parents completed questionnaires regarding demographics, sleep, and behavior. RESULTS: The final sample consisted of 309 children (mean ± standard deviation [SD] age 10.6 ± 1.3 years, male = 48%) and corresponding parent reports. On average a mean ± SD 10.2 ± 17.4 mg/day of caffeine was consumed with a range of zero to 151 mg/day. Of the children who consumed caffeine (87% of the sample), the largest contributor was coffee and tea; making up 41% of total caffeine intake, and sodas (soft drinks) contributed to 40% of caffeine intake. Total caffeine consumption was significantly associated with sleep routine (r = 0.152); morning tiredness (r = 0.129); restless sleep (r = 0.113); and internalizing behavioral problems (r = 0.128). Using path analysis, caffeine consumption was positively associated with morning tiredness (ß = 0.111, P = .050) which was positively associated with internalizing behaviors (ß = 0.432, P < .001). The addition of sleep routine and restless sleep to the model led to a complete mediation of caffeine consumption on morning tiredness, as well as a partial mediation of the association between morning tiredness and internal behaviors. CONCLUSIONS: In 8- to 12-year-olds the primary sources of caffeine are coffee/tea and sodas. Overall mean caffeine consumption is small by adult standards but has an effect on behavior and sleep in children. The effect on behavior is mediated by disrupted sleep, indicating that caffeine is a contributor to sleep problems and related behavior in children.

Cognition, temperament, and cerebral blood flow velocity in toddlers and preschool children with sleep-disordered breathing or behavioral insomnia of childhood.

BACKGROUND: Cognitive decrements, problematic behaviors, and increased cerebral blood flow velocities (CBFVs) have been reported in children aged 3-7 years with sleep-disordered breathing (SDB). Whether similar impairments exist in younger children or those with behavioral insomnia of childhood (BIC) remains unclear. This study aimed to compare cognition and temperament in children aged 1-5 years with SDB or BIC to healthy control children, and to investigate whether cognitive or behavioral deficits associated with sleep problems are related to changes in CBFV. METHOD: Toddlers and preschool-aged children (12-67 months) who had been referred for the clinical evaluation of SDB (n = 20) or BIC (n = 13) and a comparative sample of non-snoring healthy sleepers (controls; n = 77) were recruited from the community. Children underwent cognitive assessment (Mullen's Scale of Early Learning) and measurement of resting bilateral CBFV in the middle cerebral artery (MCA) using Transcranial Doppler. Parents completed temperament scales (Early Childhood or Childhood Behavior Questionnaire), a sleep problem questionnaire (Pediatric Sleep Problem Survey Instrument) and performed home-based pediatric sleep monitoring (Actigraphy and Sleep Diary). RESULTS: SDB children demonstrated impaired receptive skills, more hyperactive and energetic temperaments, and higher bilateral CBFV than controls and children with BIC. Logistic regression analyses indicated that impaired cognition, temperamental difficulties, and increased CBFV are independently associated with SDB. CONCLUSIONS: During early childhood, problematic temperaments, cognitive deficits, and altered cerebrovascular functioning are associated with SDB but not BIC. CBFV does not appear to mediate these daytime deficits and instead may be an independent outcome of SDB. The findings support the need for an early intervention in pediatric SDB.

Complex associative memory processing and sleep: a systematic review and meta-analysis of behavioural evidence and underlying EEG mechanisms.

The beneficial influence of sleep on memory consolidation is well established; however, the mechanisms by which sleep can dynamically consolidate new memories into existing networks for the continued environmental adaptation of the individual are unclear. The role of sleep in complex associative memory is an emerging field and the literature has not yet been systematically reviewed. Here, we systematically review the published literature on the role of sleep in complex associative memory processing to determine (i) if there is reasonable published evidence to support an active role for sleep facilitating complex associative processes such rule and gist extraction and false memory; (ii) to determine which sleep physiological events and states impact these processes, and to quantify the strength of these relationships through meta-analysis. Twenty-seven studies in healthy adults were identified which combined indicate a moderate effect of sleep in facilitating associative memory as tested behaviourally. Studies which have measured sleep physiology have reported mixed findings. Significant associations between sleep electrophysiology and outcome appear to be based largely on mode of acquisition. We interpret these findings as supporting reactivation based models of associative processing.

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.

Neurocognitive performance and behavior before and after treatment for sleep-disordered breathing in children.

Neurocognitive and behavioral problems are increasingly reported in children with sleep-disordered breathing (SDB). The impact of treatment for SDB on neurocognition and behavior is, therefore, an issue of increasing importance. To date, there has been little consideration given to the quality of studies when reviewing associated neurocognitive and behavioral problems in children with SDB, and furthermore, there has been little systematic review of treatment outcomes. The aim of this review was to provide an up-to-date and critical review of the current literature. Findings indicate a specific pattern of neurocognitive problems in children with SDB; however, the pattern of behavioral problems is less clear. Very few studies were found to provide a rigorous investigation of posttreatment neurocognitive and behavior outcomes. Despite this, relatively consistent improvements in global intelligence, attention, and visual spatial ability are shown; however, persistent deficits in other domains are also evident. For behavior, problems of hyperactivity, aggression or conduct problems, and somatic complaints improve following treatment. In contrast, symptoms of anxiety and social problems less consistently improve. These findings should aid in the development of more targeted investigations and well-designed studies exploring both the causative mechanisms and the treatment response for neurocognitive and behavior problems in children with SDB.

Adenotonsillectomy and neurocognitive deficits in children with Sleep Disordered Breathing.

BACKGROUND: Sleep Disordered Breathing (SDB) is a common childhood disorder that encompasses a range of sleep-related upper airway obstruction. Children with SDB demonstrate significant neurocognitive deficits. Adenotonsillectomy is the first line of treatment for SDB and whilst this improves respiratory disturbance, it remains to be established whether neurocognitive gains also result. METHODS: A total of 44 healthy snoring children aged 3-12 years awaiting adenotonsillectomy (SDB group), and 48 age and gender matched non-snoring controls from the general community, completed the study. All children underwent polysomnography and neurocognitive assessment at baseline and after a 6-month follow-up (after surgery in the snoring group). Our primary aim was to determine whether neurocognitive deficits in snoring children were significantly improved following adenotonsillectomy. RESULTS: Wide ranging neurocognitive deficits were found at baseline in SDB children compared to controls, most notably a 10 point IQ difference (P<.001) and similar deficits in language and executive function. Whilst adenotonsillectomy improved respiratory parameters and snoring frequency at 6 months post surgery, neurocognitive performance did not improve relative to controls. CONCLUSION: Adenotonsillectomy successfully treated the respiratory effects of SDB in children. However, neurocognitive deficits did not improve 6-months post-operatively.

Differences in the association between obesity and obstructive sleep apnea among children and adolescents.

STUDY OBJECTIVES: Overweight and obesity are thought to increase the risk of obstructive sleep apnea syndrome (OSAS) among children. However, previous results have been inconsistent and appear to be confounded by both ethnicity and the different ages of children studied. To determine whether the association between excess weight and OSAS varies with age across childhood, we assessed polysomnographic data from a series of Caucasian children and adolescents referred for clinical evaluation of snoring. METHODS: Sleep and OSAS severity were assessed using polysomnography in 234 children aged 2.0 to 18.0 years. All children were referred for overnight evaluation of suspected OSAS. Severity of OSAS as a function of body mass and age were then evaluated. RESULTS: Risk of OSAS among adolescents (age > or =12 years) was increased 3.5 fold with each standard-deviation increase in body mass index z-score. Risk of OSAS was not significantly increased with increasing body mass among younger children. CONCLUSIONS: Similar to adults, adolescent children show an increased risk for having OSAS in association with overweight and obesity. For Caucasian children, overweight and obesity should be considered a significant risk for OSAS among adolescents or from age 12 years, especially when in combination with other established risk factors, including snoring and adenotonsillar hypertrophy.