Age and sex effects in the EEG: development of the normal child

Age-Related Differences in Sleep Architecture and Electroencephalogram in Adolescents in the National Consortium on Alcohol and Neurodevelopment in Adolescence Sample

STUDY OBJECTIVES

To investigate age-related differences in polysomnographic and sleep electroencephalographic (EEG) measures, considering sex, pubertal stage, ethnicity, and scalp topography in a large group of adolescents in the National Consortium on Alcohol and NeuroDevelopment in Adolescence (NCANDA).

METHODS

Following an adaptation/clinical screening night, 141 healthy adolescents (12-21 y, 64 girls) had polysomnographic recordings, from which sleep staging and EEG measures were derived. The setting was the SRI International Human Sleep Laboratory and University of Pittsburgh Pediatric Sleep Laboratory.

RESULTS

Older age was associated with a lower percentage of N3 sleep, accompanied by higher percentages of N2, N1, and rapid eye movement (REM) sleep. Older boys compared with younger boys had more frequent awakenings and wakefulness after sleep onset, effects that were absent in girls. Delta (0.3-4 Hz) EEG power in nonrapid eye movement NREM sleep was lower in older than younger adolescents at all electrode sites, with steeper slopes of decline over the occipital scalp. EEG power in higher frequency bands was also lower in older adolescents than younger adolescents, with equal effects across electrodes. Percent delta power in the first NREM period was similar across age. African Americans had lower EEG power across frequency bands (delta to sigma) compared with Caucasians. Finally, replacing age with pubertal status in the models showed similar relationships.

CONCLUSIONS

Substantial differences in sleep architecture and EEG were evident across adolescence in this large group, with sex modifying some relationships. Establishment and follow-up of this cohort allows the investigation of sleep EEG-brain structural relationships and the effect of behaviors, such as alcohol and substance use, on sleep EEG maturation.

A randomized controlled trial into the effects of neurofeedback, methylphenidate, and physical activity on EEG power spectra in children with ADHD

BACKGROUND

The clinical and neurophysiological effects of neurofeedback (NF) as treatment for children with ADHD are still unclear. This randomized controlled trial (RCT) examined electroencephalogram (EEG) power spectra before and after NF compared to methylphenidate (MPH) treatment and physical activity (PA) - as semi-active control group - during resting and active (effortful) task conditions to determine whether NF can induce sustained alterations in brain function.

METHODS

Using a multicentre three-way parallel group RCT design, 112 children with a DSM-IV diagnosis of ADHD, aged between 7 and 13 years, were initially included. NF training consisted of 30 sessions of theta/beta training at Cz over a 10-week period. PA training was a semi-active control group, matched in frequency and duration. Methylphenidate was titrated using a double-blind placebo controlled procedure in 6 weeks, followed by a stable dose for 4 weeks. EEG power spectra measures during eyes open (EO), eyes closed (EC) and task (effortful) conditions were available for 81 children at pre- and postintervention (n = 29 NF, n = 25 MPH, n = 27 PA).

CLINICAL TRIALS REGISTRATION

Train Your Brain? Exercise and Neurofeedback Intervention for ADHD, https://clinicaltrials.gov/show/;NCT01363544, Ref. No. NCT01363544.

RESULTS

Both NF and MPH resulted in comparable reductions in theta power from pre- to postintervention during the EO condition compared to PA (ηp (2)  = .08 and .12). For NF, greater reductions in theta were related to greater reductions in ADHD symptoms. During the task condition, only MPH showed reductions in theta and alpha power compared to PA (ηp (2)  = .10 and .12).

CONCLUSIONS

This study provides evidence for specific neurophysiological effects after theta/beta NF and MPH treatment in children with ADHD. However, for NF these effects did not generalize to an active task condition, potentially explaining reduced behavioural effects of NF in the classroom.

Coherence in children with AD/HD and excess alpha power in their EEG

OBJECTIVE

This study investigated differences in EEG coherence measures between two groups of children with Attention-Deficit/Hyperactivity Disorder (AD/HD) - one with the more common EEG profile (increased theta), and a group with excess alpha activity as the dominant EEG abnormality.

METHODS

26 children (aged 9-13years) with AD/HD were included in each of the excess-theta and excess-alpha groups, and were age- and sex-matched with 26 control subjects. EEG was recorded from 19 electrode sites during an eyes-closed resting condition. Wave-shape coherence was calculated for eight intrahemispheric and eight interhemispheric electrode pairs, for the delta, theta, alpha and beta bands.

RESULTS

In comparison with the controls, the excess-theta AD/HD group had increased theta intrahemispheric coherences at short-medium inter-electrode distances. Frontally, the excess-theta AD/HD group had increased interhemispheric theta and reduced beta coherences. The excess-alpha group primarily showed increased slow wave (delta and theta) intrahemispheric coherence at short-medium inter-electrode distances, and reduced alpha coherence at longer inter-electrode distances, compared with controls. An increase in frontal interhemispheric theta coherence was also found.

CONCLUSIONS

These results suggest that AD/HD children with excess alpha power have an underlying connectivity dysfunction in the frontal lobes, which is found in common with other subjects with the excess-theta EEG profile. However, a number of qualitative differences exist that could be associated with other aspects of the AD/HD diagnosis. The excess-alpha group appeared to have fewer frontal-lobe abnormalities than the excess-theta AD/HD group.

SIGNIFICANCE

This is the first study to investigate coherence in AD/HD children who have the atypical profile of increased alpha power in their EEG.

Posterior alpha oscillations reflect attentional problems in boys with Attention Deficit Hyperactivity Disorder

OBJECTIVE

This study aimed to characterize alpha modulations in children with ADHD in relation to their attentional performance.

METHODS

The posterior alpha activity (8-12Hz) was measured in 30 typically developing children and 30 children with ADHD aged 7-10years, using EEG while they performed a visuospatial covert attention task. We focused the analyses on typically developing boys (N=9) and boys with ADHD (N=17).

RESULTS

Alpha activity in typically developing boys was similar to previous results of healthy adults: it decreased in the hemisphere contralateral to the attended hemifield, whereas it relatively increased in the other hemisphere. However, in boys with ADHD this hemispheric lateralization in the alpha band was not obvious (group contrast, p=.018). A robust relation with behavioral performance was lacking in both groups.

CONCLUSIONS

The ability to modulate alpha oscillations in visual regions with the allocation of spatial attention was clearly present in typically developing boys, but not in boys with ADHD.

SIGNIFICANCE

These results open up the possibility to further study the underlying mechanisms of ADHD by examining how differences in the fronto-striatal network might explain different abilities in modulating the alpha band activity.

Normalization of EEG activity among previously institutionalized children placed into foster care: A 12-year follow-up of the Bucharest Early Intervention Project

Extreme social and cognitive deprivation as a result of institutional care has profound effects on developmental outcomes across multiple domains for many abandoned or orphaned children. The Bucharest Early Intervention Project (BEIP) examines the outcomes for children originally placed in institutions who were assessed comprehensively and then randomized to foster care (FCG) or care as usual (CAUG) and followed longitudinally. Here we report on the brain electrical activity (electroencephalogram: EEG) of 12-year-old children enrolled in the BEIP. Previous reports suggested improvement in resting EEG activity for the group of children placed in the foster care intervention, particularly those placed before 24 months of age compared to children who were randomized to CAUG or those placed into families after this age. At 12 years, differences between those in the FCG and those in the CAUG persist in the alpha band (8-13 Hz), but not in higher frequency bands (i.e. in the beta band; 15-30 Hz), except in those children placed into the FCG who remained in high quality care environments over the course of the study. These findings highlight the importance of maintaining a stable high quality caregiving environment, particularly for children exposed to early psychosocial deprivation, for promoting healthy brain development.

To Stroop or not to Stroop: Sex-related differences in brain-behavior associations during early childhood

Executive functions (EFs) are linked with optimal cognitive and social-emotional development. Despite behavioral evidence of sex differences in early childhood EF, little is known about potential sex differences in corresponding brain-behavior associations. The present study examined changes in 4-year-olds' 6-9 Hz EEG power in response to increased executive processing demands (i.e., "Stroop-like" vs. "non-Stroop" day-night tasks). Although there were no sex differences in task performance, an examination of multiple scalp electrode sites revealed that boys exhibited more widespread changes in EEG power as compared to girls. Further, multiple regression analyses controlling for maternal education and non-EF performance indicated that individual differences in boys' and girls' EF performance were associated with different frontal neural correlates (i.e., different frontal scalp sites and different measures of EEG power). These data reveal valuable information concerning sex differences in the neural systems underlying executive processing during early childhood.

Electrophysiological biomarkers of diagnosis and outcome in neurodevelopmental disorders

PURPOSE OF REVIEW

The heterogeneity in clinical presentation and outcome in neurodevelopmental disorders such as attention deficit hyperactivity disorder (ADHD) autism spectrum disorder (ASD) necessitates the identification and validation of biomarkers that can guide diagnosis, predict developmental outcomes, and monitor treatment response. Electrophysiology holds both practical and theoretical advantages as a clinical biomarker in neurodevelopmental disorders, and considerable effort has been invested in the search for electroencephalography (EEG) biomarkers in ADHD and ASD.

RECENT FINDINGS

Here, we discuss the major themes in the evaluation of biomarkers and then review studies that have applied EEG to better inform diagnosis, focusing on the controversy surrounding the theta:beta ratio in ADHD; prediction of risk, highlighting recent studies of infants at high risk for ASD; and treatment monitoring, presenting new efforts in the redefinition of outcome measures in clinical trials of ASD treatment.

SUMMARY

We conclude that insights gained from EEG studies will contribute significantly to a more mechanistic understanding of these disorders and to the development of biomarkers that can assist with diagnosis, prognosis, and intervention. There is a need, however, to utilize approaches that accommodate, rather than ignore, diagnostic heterogeneity and individual differences.

Deficient Event-Related Theta Oscillations in Individuals at Risk for Alcoholism: A Study of Reward Processing and Impulsivity Features

BACKGROUND

Individuals at high risk to develop alcoholism often manifest neurocognitive deficits as well as increased impulsivity. Event-related oscillations (EROs) have been used to effectively measure brain (dys)function during cognitive tasks in individuals with alcoholism and related disorders and in those at risk to develop these disorders. The current study examines ERO theta power during reward processing as well as impulsivity in adolescent and young adult subjects at high risk for alcoholism.

METHODS

EROs were recorded during a monetary gambling task (MGT) in 12-25 years old participants (N = 1821; males = 48%) from high risk alcoholic families (HR, N = 1534) and comparison low risk community families (LR, N = 287) from the Collaborative Study on the Genetics of Alcoholism (COGA). Impulsivity scores and prevalence of externalizing diagnoses were also compared between LR and HR groups.

RESULTS

HR offspring showed lower theta power and decreased current source density (CSD) activity than LR offspring during loss and gain conditions. Younger males had higher theta power than younger females in both groups, while the older HR females showed more theta power than older HR males. Younger subjects showed higher theta power than older subjects in each comparison. Differences in topography (i.e., frontalization) between groups were also observed. Further, HR subjects across gender had higher impulsivity scores and increased prevalence of externalizing disorders compared to LR subjects.

CONCLUSIONS

As theta power during reward processing is found to be lower not only in alcoholics, but also in HR subjects, it is proposed that reduced reward-related theta power, in addition to impulsivity and externalizing features, may be related in a predisposition to develop alcoholism and related disorders.

Reward processing deficits and impulsivity in high-risk offspring of alcoholics: A study of event-related potentials during a monetary gambling task

BACKGROUND

Individuals at high risk to develop alcoholism often manifest neurocognitive deficits as well as increased impulsivity. The goal of the present study is to elucidate reward processing deficits, externalizing disorders, and impulsivity as elicited by electrophysiological, clinical and behavioral measures in subjects at high risk for alcoholism from families densely affected by alcoholism in the context of brain maturation across age groups and gender.

METHODS

Event-related potentials (ERPs) and current source density (CSD) during a monetary gambling task (MGT) were measured in 12-25 year old offspring (N=1864) of families in the Collaborative Study on the Genetics of Alcoholism (COGA) Prospective study; the high risk (HR, N=1569) subjects were from families densely affected with alcoholism and the low risk (LR, N=295) subjects were from community families. Externalizing disorders and impulsivity scores were also compared between LR and HR groups.

RESULTS

HR offspring from older (16-25 years) male and younger (12-15 years) female subgroups showed lower P3 amplitude than LR subjects. The amplitude decrement was most prominent in HR males during the loss condition. Overall, P3 amplitude increase at anterior sites and decrease at posterior areas were seen in older compared to younger subjects, suggesting frontalization during brain maturation. The HR subgroups also exhibited hypofrontality manifested as weaker CSD activity during both loss and gain conditions at frontal regions. Further, the HR subjects had higher impulsivity scores and increased prevalence of externalizing disorders. P3 amplitudes during the gain condition were negatively correlated with impulsivity scores.

CONCLUSIONS

Older male and younger female HR offspring, compared to their LR counterparts, manifested reward processing deficits as indexed by lower P3 amplitude and weaker CSD activity, along with higher prevalence of externalizing disorders and higher impulsivity scores.

SIGNIFICANCE

Reward related P3 is a valuable measure reflecting neurocognitive dysfunction in subjects at risk for alcoholism, as well as to characterize reward processing and brain maturation across gender and age group.

Heightened Delta Power during Slow-Wave-Sleep in Patients with Rett Syndrome Associated with Poor Sleep Efficiency

Sleep problems are commonly reported in Rett syndrome (RTT); however the electroencephalographic (EEG) biomarkers underlying sleep dysfunction are poorly understood. The aim of this study was to analyze the temporal evolution of quantitative EEG (qEEG) biomarkers in overnight EEGs recorded from girls (2-9 yrs. old) diagnosed with RTT using a non-traditional automated protocol. In this study, EEG spectral analysis identified high delta power cycles representing slow wave sleep (SWS) in 8-9h overnight sleep EEGs from the frontal, central and occipital leads (AP axis), comparing age-matched girls with and without RTT. Automated algorithms quantitated the area under the curve (AUC) within identified SWS cycles for each spectral frequency wave form. Both age-matched RTT and control EEGs showed similar increasing trends for recorded delta wave power in the EEG leads along the antero-posterior (AP). RTT EEGs had significantly fewer numbers of SWS sleep cycles; therefore, the overall time spent in SWS was also significantly lower in RTT. In contrast, the AUC for delta power within each SWS cycle was significantly heightened in RTT and remained heightened over consecutive cycles unlike control EEGs that showed an overnight decrement of delta power in consecutive cycles. Gamma wave power associated with these SWS cycles was similar to controls. However, the negative correlation of gamma power with age (r = -.59; p<0.01) detected in controls (2-5 yrs. vs. 6-9 yrs.) was lost in RTT. Poor % SWS (i.e., time spent in SWS overnight) in RTT was also driven by the younger age-group. Incidence of seizures in RTT was associated with significantly lower number of SWS cycles. Therefore, qEEG biomarkers of SWS in RTT evolved temporally and correlated significantly with clinical severity.

Development of Network Synchronization Predicts Language Abilities

Synchronization of oscillations among brain areas is understood to mediate network communication supporting cognition, perception, and language. How task-dependent synchronization during word production develops throughout childhood and adolescence, as well as how such network coherence is related to the development of language abilities, remains poorly understood. To address this, we recorded magnetoencephalography while 73 participants aged 4-18 years performed a verb generation task. Atlas-guided source reconstruction was performed, and phase synchronization among regions was calculated. Task-dependent increases in synchronization were observed in the theta, alpha, and beta frequency ranges, and network synchronization differences were observed between age groups. Task-dependent synchronization was strongest in the theta band, as were differences between age groups. Network topologies were calculated for brain regions associated with verb generation and were significantly associated with both age and language abilities. These findings establish the maturational trajectory of network synchronization underlying expressive language abilities throughout childhood and adolescence and provide the first evidence for an association between large-scale neurophysiological network synchronization and individual differences in the development of language abilities.

Correlation of EEG with neuropsychological status in children with epilepsy

OBJECTIVE

To determine correlations of the EEG frequency spectrum with neuropsychological status in children with idiopathic epilepsy.

METHODS

Forty-six children ages 8-18 years old with idiopathic epilepsy were retrospectively identified and analyzed for correlations between EEG spectra and neuropsychological status using multivariate linear regression. In addition, the theta/beta ratio, which has been suggested as a clinically useful EEG marker of attention-deficit hyperactivity disorder (ADHD), and an EEG spike count were calculated for each subject.

RESULTS

Neuropsychological status was highly correlated with posterior alpha (8-15 Hz) EEG activity in a complex way, with both positive and negative correlations at lower and higher alpha frequency sub-bands for each cognitive task in a pattern that depends on the specific cognitive task. In addition, the theta/beta ratio was a specific but insensitive indicator of ADHD status in children with epilepsy; most children both with and without epilepsy have normal theta/beta ratios. The spike count showed no correlations with neuropsychological status.

CONCLUSIONS

(1) The alpha rhythm may have at least two sub-bands which serve different purposes. (2) The theta/beta ratio is not a sensitive indicator of ADHD status in children with epilepsy. (3) The EEG frequency spectrum correlates more robustly with neuropsychological status than spike count analysis in children with idiopathic epilepsy.

SIGNIFICANCE

(1) The role of posterior alpha rhythms in cognition is complex and can be overlooked if EEG spectral resolution is too coarse or if neuropsychological status is assessed too narrowly. (2) ADHD in children with idiopathic epilepsy may involve different mechanisms from those in children without epilepsy. (3) Reliable correlations with neuropsychological status require longer EEG samples when using spike count analysis than when using frequency spectra.

Music training alters the course of adolescent auditory development

Fundamental changes in brain structure and function during adolescence are well-characterized, but the extent to which experience modulates adolescent neurodevelopment is not. Musical experience provides an ideal case for examining this question because the influence of music training begun early in life is well-known. We investigated the effects of in-school music training, previously shown to enhance auditory skills, versus another in-school training program that did not focus on development of auditory skills (active control). We tested adolescents on neural responses to sound and language skills before they entered high school (pretraining) and again 3 y later. Here, we show that in-school music training begun in high school prolongs the stability of subcortical sound processing and accelerates maturation of cortical auditory responses. Although phonological processing improved in both the music training and active control groups, the enhancement was greater in adolescents who underwent music training. Thus, music training initiated as late as adolescence can enhance neural processing of sound and confer benefits for language skills. These results establish the potential for experience-driven brain plasticity during adolescence and demonstrate that in-school programs can engender these changes.

EEG activity in children with Asperger's Syndrome

OBJECTIVE

This study investigated differences in the EEG power and coherence of children with Asperger's Syndrome.

METHOD

Twenty boys with Asperger's Syndrome, aged 7-12 years, and an age and sex matched control group, participated in this study. The EEG was recorded during an eyes-closed resting condition from 19 electrode sites, which were clustered into nine regions prior to analysis. One minute of trace was analysed using Fourier transformations to obtain both absolute and relative power estimates in the delta, theta, alpha and beta frequency bands. Wave-shape coherence was calculated for 8 intrahemispheric and 8 interhemispheric electrode pairs.

RESULTS

The Asperger's group had a global increase in absolute delta and an anterior increase in relative delta. Both absolute and relative theta were globally increased and relative alpha was globally decreased. Subjects with Asperger's Syndrome exhibited a broad pattern of reduced hemispheric asymmetry in intrahemispheric coherence. Reduced anterior interhemispheric coherence in the alpha and beta bands was also found in the Asperger's Syndrome group.

CONCLUSIONS

These results suggest the existence of frontal lobe abnormalities in children with Asperger's Syndrome, and possible abnormalities in normal CNS maturational processes.

SIGNIFICANCE

This is the first major study to investigate EEG power and coherence anomalies in children with Asperger's Syndrome.

Neurofeedback, pharmacological treatment and behavioral therapy in hyperactivity: Multilevel analysis of treatment effects on electroencephalography

The purpose of this study was to investigate the efficacy of neurofeedback, pharmacological treatment and behavioral therapy in Attention Deficit Hyperactivity Disorder (ADHD) through a controlled, randomized, multigroup design, with pre-, post- and follow-up treatment phases. The objectives of this study are: a) to analyze individual trajectories over time of each child in treatment, from specific measures of EEG (theta/beta ratio/TBR) considering age and sex and b) to determine the therapeutic effect on attentional and behavioral variables evaluated through the Integrated Visual and Auditory Continuous Performance Test. A total of 57 children (7-14 years) diagnosed with ADHD, were randomly assigned to one of the following experimental conditions: 1) 30 Theta/Beta training sessions, 2) Methylphenidate treatment and, 3) Behavior therapy administered according to a cognitive-behavioral protocol based on manuals. Data were analyzed using a Multilevel Longitudinal Regression Model. Results show that administered treatments are effective and cause similar effects on TBR variable, with no differences between them. However, significant differences were observed in the global attention (p=.002), auditory attention (p=.017) and visual attention (p=.028).

Neurofeedback and its possible relevance for the treatment of Tourette syndrome

Neurofeedback is an increasingly recognized therapeutic option in various neuropsychiatric disorders to treat dysfunctions in cognitive control as well as disorder-specific symptoms. In this review we propose that neurofeedback may also reflect a valuable therapeutic option to treat executive control functions in Gilles-de-la-Tourette syndrome (GTS). Deficits in executive control functions when ADHD symptoms appear in GTS likely reflect pathophysiological processes in cortico-thalamic-striatal circuits and may also underlie the motor symptoms in GTS. Such executive control deficits evident in comorbid GTS/ADHD depend on neurophysiological processes well-known to be modifiable by neurofeedback. However, so far efforts to use neurofeedback to treat cognitive dysfunctions are scarce. We outline why neurofeedback should be considered a promising treatment option, what forms of neurofeedback may prove to be most effective and how neurofeedback may be implemented in existing intervention strategies to treat comorbid GTS/ADHD and associated dysfunctions in cognitive control. As cognitive control deficits in GTS mostly appear in comorbid GTS/ADHD, neurofeedback may be most useful in this frequent combination of disorders.

Transition dynamics of EEG-based network microstates during mental arithmetic and resting wakefulness reflects task-related modulations and developmental changes

We studied how maturation influences the organization of functional brain networks engaged during mental calculations and in resting state. Surface EEG measurements from 20 children (8-12 years) and 25 students (21-26 years) were analyzed. Interregional synchronization of brain activity was quantified by means of Phase Lag Index and for various frequency bands. Based on these pairwise estimates of functional connectivity, we formed graphs which were then characterized in terms of local structure [local efficiency (LE)] and overall integration (global efficiency). The overall data analytic scheme was applied twice, in a static and time-varying mode. Our results showed a characteristic trend: functional segregation dominates the network organization of younger brains. Moreover, in childhood, the overall functional network possesses more prominent small-world network characteristics than in early acorrect in xmldulthood in accordance with the Neural Efficiency Hypothesis. The above trends were intensified by the time-varying approach and identified for the whole set of tested frequency bands (from δ to low γ). By mapping the time-indexed connectivity patterns to multivariate timeseries of nodal LE measurements, we carried out an elaborate study of the functional segregation dynamics and demonstrated that the underlying network undergoes transitions between a restricted number of stable states, that can be thought of as "network-level microstates". The rate of these transitions provided a robust marker of developmental and task-induced alterations, that was found to be insensitive to reference montage and independent component analysis denoising.

Electroencephalography and externalizing behavior: a meta-analysis

Electroencephalography (EEG) has been used to examine the possibility of dysfunctional brain activity in externalizing behavior, but findings across studies have been inconsistent. Furthermore, studies of attention-deficit/hyperactivity disorder (ADHD) versus other externalizing behaviors, such as disruptive behavior disorders or antisocial behavior, have developed parallel literatures. The purpose of the present study was to reconcile these two literatures. A meta-analysis of 62 studies of EEG power at rest in relationship to externalizing behaviors was performed. Results of the meta-analyses showed significantly higher delta (Hedges's g=0.25) and theta power (g=0.40) and lower beta power (g=-0.22) in externalizing participants compared to controls. Alpha (g=-0.26) and gamma power (g=-0.26) were marginally lower in externalizing samples. Results were not moderated by type of externalizing behavior. Overall, the results of the meta-analyses were consistent with the hypoarousal theory of externalizing behavior.

State-related electroencephalographic deviances in attention deficit hyperactivity disorder

This study investigated the stability and state-related characteristics of electroencephalographic (EEG) deviances in attention-deficit/hyperactivity disorder (ADHD). Three minutes resting EEG with eyes closed and eyes open were compared between 21 children with ADHD and 29 typically developing children. Across resting conditions, children with ADHD exhibited divergent topographic distribution for theta, alpha and beta power compared to typically developing children. In addition, less alpha and theta suppression to eye opening was found in children with ADHD, but only in those without comorbid ODD/CD. Findings of the present study refer to a consistent divergence in topographic distribution in ADHD across resting state conditions, yet demonstrate that state-related factors and comorbidity may also contribute to resting EEG deviances in ADHD. The state-related findings are in accord with several theoretical accounts emphasizing the role of contextual and state factors defining deficits in ADHD.

Longitudinal study of EEG frequency maturation and power changes in children on the Russian North

The aim of the study was to reveal longitudinal changes in electroencephalogram spectral power and frequency (percentage frequency composition of EEG and alpha peak frequency) patterns in normal children from northern Russia. Fifteen children (9 girls and 6 boys) participated in the study. The resting state (eyes closed) EEGs were recorded yearly (2005-2013) from age 8 to age 16-17 for each child. EEG frequency patterns were estimated as the percentages of waves with a 1 Hz step revealed by measuring the interval durations between points crossing zero (isoline) by a curve. EEG spectral power changes were analyzed for delta (1.5-4 Hz), theta (4-7.5 Hz), alpha-1 (7.5-9.5 Hz), alpha-2 (9.5-12.5 Hz), beta-1 (12.5-18 Hz) and beta-2 (18-30 Hz) bands. According to the frequency composition of the EEG signals fast synchronous, polymorphous synchronous, polymorphous desynchronous and slow synchronous types of children EEG were revealed. These EEG types were relatively stable during adolescence. In these EEG types, the frequency patterns and spectral power dynamics with age had several common and specific features. Slow wave percentage and spectral power in the delta band remarkably decreased with age in all groups. Starting from the theta band the EEG types were characterized by different EEG spectral power changes with age. In fast synchronous EEG type, the theta and alpha-1 EEG power decreased, and the alpha-2 power increased in the occipital and parietal areas. The polymorphous synchronous type was characterized by increased both the alpha-1 and alpha-2 power with regional peculiarities. In the polymorphous desynchronous type spectral power in all bands decreased with age, and in the slow synchronous type, the alpha-1 power massively increased with age. Obtained results suggest predictive strength of the spatial-frequency patterns in EEG for its following maturation through the years.

Oscillations, networks, and their development: MEG connectivity changes with age

Magnetoencephalographic (MEG) investigations of inter-regional amplitude correlations have yielded new insights into the organization and neurophysiology of resting-state networks (RSNs) first identified using fMRI. Inter-regional MEG amplitude correlations in adult RSNs have been shown to be most prominent in alpha and beta frequency ranges and to express strong congruence with RSN topologies found using fMRI. Despite such advances, little is known about how oscillatory connectivity in RSNs develops throughout childhood and adolescence. This study used a novel fMRI-guided MEG approach to investigate the maturation of resting-state amplitude correlations in physiologically relevant frequency ranges within and among six RSNs in 59 participants, aged 6-34 years. We report age-related increases in inter-regional amplitude correlations that were largest in alpha and beta frequency bands. In contrast to fMRI reports, these changes were observed both within and between the various RSNs analyzed. Our results provide the first evidence of developmental changes in spontaneous neurophysiological connectivity in source-resolved RSNs, which indicate increasing integration within and among intrinsic functional brain networks throughout childhood, adolescence, and early adulthood.

Decreases in energy and increases in phase locking of event-related oscillations to auditory stimuli occur during adolescence in human and rodent brain

Synchrony of phase (phase locking) of event-related oscillations (EROs) within and between different brain areas has been suggested to reflect communication exchange between neural networks and as such may be a sensitive and translational measure of changes in brain remodeling that occur during adolescence. This study sought to investigate developmental changes in EROs using a similar auditory event-related potential (ERP) paradigm in both rats and humans. Energy and phase variability of EROs collected from 38 young adult men (aged 18-25 years), 33 periadolescent boys (aged 10-14 years), 15 male periadolescent rats [at postnatal day (PD) 36] and 19 male adult rats (at PD103) were investigated. Three channels of ERP data (frontal cortex, central cortex and parietal cortex) were collected from the humans using an 'oddball plus noise' paradigm that was presented under passive (no behavioral response required) conditions in the periadolescents and under active conditions (where each subject was instructed to depress a counter each time he detected an infrequent target tone) in adults and adolescents. ERPs were recorded in rats using only the passive paradigm. In order to compare the tasks used in rats to those used in humans, we first studied whether three ERO measures [energy, phase locking index (PLI) within an electrode site and phase difference locking index (PDLI) between different electrode sites] differentiated the 'active' from 'passive' ERP tasks. Secondly, we explored our main question of whether the three ERO measures differentiated adults from periadolescents in a similar manner in both humans and rats. No significant changes were found in measures of ERO energy between the active and passive tasks in the periadolescent human participants. There was a smaller but significant increase in PLI but not PDLI as a function of active task requirements. Developmental differences were found in energy, PLI and PDLI values between the periadolescents and adults in both the rats and the human participants. Neuronal synchrony as indexed by PLI and PDLI was significantly higher to the infrequent (target) tone compared to the frequent (nontarget) tone in all brain sites in all of the regions of interest time-frequency intervals. Significantly higher ERO energy and significantly lower synchrony was seen in the periadolescent humans and rats compared to their adult counterparts. Taken together these findings are consistent with the hypothesis that adolescent remodeling of the brain includes decreases in energy and increases in synchrony over a wide frequency range both within and between neuronal networks and that these effects are conserved over evolution.

Differential resting-state EEG patterns associated with comorbid depression in Internet addiction

OBJECTIVE

Many researchers have reported a relationship between Internet addiction and depression. In the present study, we compared the resting-state quantitative electroencephalography (QEEG) activity of treatment-seeking patients with comorbid Internet addiction and depression with those of treatment-seeking patients with Internet addiction without depression, and healthy controls to investigate the neurobiological markers that differentiate pure Internet addiction from Internet addiction with comorbid depression.

METHOD

Thirty-five patients diagnosed with Internet addiction and 34 age-, sex-, and IQ-matched healthy controls were enrolled in this study. Patients with Internet addiction were divided into two groups according to the presence (N=18) or absence (N=17) of depression. Resting-state, eye-closed QEEG was recorded, and the absolute and relative power of the brain were analyzed.

RESULTS

The Internet addiction group without depression had decreased absolute delta and beta powers in all brain regions, whereas the Internet addiction group with depression had increased relative theta and decreased relative alpha power in all regions. These neurophysiological changes were not related to clinical variables.

CONCLUSION

The current findings reflect differential resting-state QEEG patterns between both groups of participants with Internet addiction and healthy controls and also suggest that decreased absolute delta and beta powers are neurobiological markers of Internet addiction.

The effect of alpha rhythm sleep on EEG activity and individuals' attention

[Purpose] This study examined whether the alpha rhythm sleep alters the EEG activity and response time in the attention and concentration tasks. [Subjects and Methods] The participants were 30 healthy university students, who were randomly and equally divided into two groups, the experimental and control groups. They were treated using the Happy-sleep device or a sham device, respectively. All participants had a one-week training period. Before and after training sessions, a behavioral task test was performed and EEG alpha waves were measured to confirm the effectiveness of training on cognitive function. [Results] In terms of the behavioral task test, reaction time (RT) variations in the experimental group were significantly larger than in the control group for the attention item. Changes in the EEG alpha power in the experimental group were also significantly larger than those of the control group. [Conclusions] These findings suggest that sleep induced using the Happy-sleep device modestly enhances the ability to pay attention and focus during academic learning.

Topological organization of the human brain functional connectome across the lifespan

Human brain function undergoes complex transformations across the lifespan. We employed resting-state functional MRI and graph-theory approaches to systematically chart the lifespan trajectory of the topological organization of human whole-brain functional networks in 126 healthy individuals ranging in age from 7 to 85 years. Brain networks were constructed by computing Pearson's correlations in blood-oxygenation-level-dependent temporal fluctuations among 1024 parcellation units followed by graph-based network analyses. We observed that the human brain functional connectome exhibited highly preserved non-random modular and rich club organization over the entire age range studied. Further quantitative analyses revealed linear decreases in modularity and inverted-U shaped trajectories of local efficiency and rich club architecture. Regionally heterogeneous age effects were mainly located in several hubs (e.g., default network, dorsal attention regions). Finally, we observed inverse trajectories of long- and short-distance functional connections, indicating that the reorganization of connectivity concentrates and distributes the brain's functional networks. Our results demonstrate topological changes in the whole-brain functional connectome across nearly the entire human lifespan, providing insights into the neural substrates underlying individual variations in behavior and cognition. These results have important implications for disease connectomics because they provide a baseline for evaluating network impairments in age-related neuropsychiatric disorders.

Region-Specific Slowing of Alpha Oscillations is Associated with Visual-Perceptual Abilities in Children Born Very Preterm

Children born very preterm (≤32 weeks gestational age) without major intellectual or neurological impairments often express selective deficits in visual-perceptual abilities. The alterations in neurophysiological development underlying these problems, however, remain poorly understood. Recent research has indicated that spontaneous alpha oscillations are slowed in children born very preterm, and that atypical alpha-mediated functional network connectivity may underlie selective developmental difficulties in visual-perceptual ability in this group. The present study provides the first source-resolved analysis of slowing of spontaneous alpha oscillations in very preterm children, indicating alterations in a distributed set of brain regions concentrated in areas of posterior parietal and inferior temporal regions associated with visual perception, as well as prefrontal cortical regions and thalamus. We also uniquely demonstrate that slowing of alpha oscillations is associated with selective difficulties in visual-perceptual ability in very preterm children. These results indicate that region-specific slowing of alpha oscillations contribute to selective developmental difficulties prevalent in this population.

Reduced Theta Connectivity during Set-Shifting in Children with Autism

Autism spectrum disorder (ASD) is a characterized by deficits in social cognition and executive function. An area of particular difficulty for children with ASD is cognitive flexibility, such as the ability to shift between attentional or response sets. The biological basis of such deficits remains poorly understood, although atypical development of structural and functional brain connectivity have been reported in ASD, suggesting that disruptions of normal patterns of inter-regional communication may contribute to cognitive problems in this group. The present magnetoencephalography study measured inter-regional phase synchronization while children with ASD and typically developing matched controls (6–14 years of age) performed a set-shifting task. Reduced theta-band phase synchronization was observed in children with ASD during extradimensional set-shifting. This reduction in task-dependent inter-regional connectivity encompassed numerous areas including multiple frontal lobe regions, and indicates that problems with communication among brain areas may contribute to difficulties with executive function in ASD.

Neonatal pain-related stress, functional cortical activity and visual-perceptual abilities in school-age children born at extremely low gestational age

Children born very prematurely (< or =32 weeks) often exhibit visual-perceptual difficulties at school-age, even in the absence of major neurological impairment. The alterations in functional brain activity that give rise to such problems, as well as the relationship between adverse neonatal experience and neurodevelopment, remain poorly understood. Repeated procedural pain-related stress during neonatal intensive care has been proposed to contribute to altered neurocognitive development in these children. Due to critical periods in the development of thalamocortical systems, the immature brain of infants born at extremely low gestational age (ELGA; < or =28 weeks) may have heightened vulnerability to neonatal pain. In a cohort of school-age children followed since birth we assessed relations between functional brain activity measured using magnetoencephalogragy (MEG), visual-perceptual abilities and cumulative neonatal pain. We demonstrated alterations in the spectral structure of spontaneous cortical oscillatory activity in ELGA children at school-age. Cumulative neonatal pain-related stress was associated with changes in background cortical rhythmicity in these children, and these alterations in spontaneous brain oscillations were negatively correlated with visual-perceptual abilities at school-age, and were not driven by potentially confounding neonatal variables. These findings provide the first evidence linking neonatal pain-related stress, the development of functional brain activity, and school-age cognitive outcome in these vulnerable children.

Developmental change in EEG theta activity in the medial prefrontal cortex during response control

Cognitive control functions continue to improve from infancy until early adulthood, allowing flexible adaptation to a complex environment. However, it remains controversial how this development in cognitive capabilities is mediated by changes in cortical activity: both age-related increases and decreases of mediofrontal neural activity have been observed and interpreted as neural underpinnings of this functional development. To better understand this developmental process, we examined EEG theta activity in the mediofrontal region using a Go/No-go response control task. We found that both pre-stimulus baseline theta-power and theta-power during the response control task, without baseline-correction, decreased with age. Conversely, when task-related theta-power was baseline corrected (using a ratio method), it exhibited a positive developmental trajectory. The age-related theta-power increase was source-localized to the anterior cingulate cortex. This increase in theta activity also partially mediated age-related improvements in response control and was greatest in a condition that demanded greater effort. Theta activity in older children also showed greater temporal reliability across trials as measured by inter-trial phase-coherence. Interestingly, directly subtracting baseline activity from task-related activity did not yield significant developmental effects, which highlights the necessity of separating and contrasting the pre-stimulus baseline with task-related processing in the understanding of neurodevelopmental changes.

On the application of quantitative EEG for characterizing autistic brain: a systematic review

Autism-Spectrum Disorders (ASD) are thought to be associated with abnormalities in neural connectivity at both the global and local levels. Quantitative electroencephalography (QEEG) is a non-invasive technique that allows a highly precise measurement of brain function and connectivity. This review encompasses the key findings of QEEG application in subjects with ASD, in order to assess the relevance of this approach in characterizing brain function and clustering phenotypes. QEEG studies evaluating both the spontaneous brain activity and brain signals under controlled experimental stimuli were examined. Despite conflicting results, literature analysis suggests that QEEG features are sensitive to modification in neuronal regulation dysfunction which characterize autistic brain. QEEG may therefore help in detecting regions of altered brain function and connectivity abnormalities, in linking behavior with brain activity, and subgrouping affected individuals within the wide heterogeneity of ASD. The use of advanced techniques for the increase of the specificity and of spatial localization could allow finding distinctive patterns of QEEG abnormalities in ASD subjects, paving the way for the development of tailored intervention strategies.

Rhythmic cortical neurons increase their oscillations and sculpt basal ganglia signaling during motor learning

The function and modulation of neural circuits underlying motor skill may involve rhythmic oscillations (Feller, 1999; Marder and Goaillard, 2006; Churchland et al., 2012). In the proposed pattern generator for birdsong, the cortical nucleus HVC, the frequency and power of oscillatory bursting during singing increases with development (Crandall et al., 2007; Day et al., 2009). We examined the maturation of cellular activity patterns that underlie these changes. Single unit ensemble recording combined with antidromic identification (Day et al., 2011) was used to study network development in anesthetized zebra finches. Autocovariance quantified oscillations within single units. A subset of neurons oscillated in the theta/alpha/mu/beta range (8-20 Hz), with greater power in adults compared to juveniles. Across the network, the normalized oscillatory power in the 8-20 Hz range was greater in adults than juveniles. In addition, the correlated activity between rhythmic neuron pairs increased with development. We next examined the functional impact of the oscillators on the output neurons of HVC. We found that the firing of oscillatory neurons negatively correlated with the activity of cortico-basal ganglia neurons (HVC(X)s), which project to Area X (the song basal ganglia). If groups of oscillators work together to tonically inhibit and precisely control the spike timing of adult HVC(X)s with coordinated release from inhibition, then the activity of HVC(X)s in juveniles should be decreased relative to adults due to uncorrelated, tonic inhibition. Consistent with this hypothesis, HVC(X)s had lower activity in juveniles. These data reveal network changes that shape cortical-to-basal ganglia signaling during motor learning.

Gender impact on electrophysiological activity of the brain

Gender is presumed to be one of the factors causing interindividual variability in the brain's electrophysiological parameters. Our aim was to characterize the role of gender in visual evoked potentials (VEPs), event-related potentials (ERPs), visual mismatch negativity (vMMN) and the spectral characteristics of the EEG. We examined 42 healthy volunteers (21 women and 21 men, aged 20-29 years). We measured VEPs in response to pattern-reversal and motion-onset stimulation, ERPs in an oddball paradigm and vMMN in response to a combination of motion directions presented in the visual periphery. P100 peak latency for 40' reversal VEPs was significantly shorter in women than in men as determined using a non-parametric Wilcoxon signed-rank test. In addition, women showed higher relative EEG spectral power in the alpha band (p=0.023) and lower power in the theta band (p=0.004). Our results in this small but homogeneous group of subjects confirm previously reported gender influences on pattern-reversal VEPs and the EEG frequency spectrum. Gender should be taken into consideration in establishing norms on these measures. We found no statistically significant differences between women and men for any of the other stimuli presented.

Resting state brain oscillations and symptom profiles in attention deficit/hyperactivity disorder

Our perspective on resting-state electroencephalogram (EEG) is that it provides a window into the substrate of cognitive and perceptual processing, reflecting the dynamic potential of the brain's current functional state. In an extended research program into the electrophysiology of attention deficit/hyperactivity disorder (AD/HD), we have examined resting-state EEG power and coherence, and event-related potentials (ERPs), in children, adolescents, and adults with the disorder. We sought initially to identify consistent AD/HD anomalies in these measures, relative to normal control subjects, and then to understand how these differences related to existing models of AD/HD. An emergent strand in this program has been to clarify the EEG correlates of "arousal" and to understand the role of arousal dysfunction as a core anomaly in AD/HD. To date, findings in this strand serve to rule out a commonly held dictum in the AD/HD field: that elevated theta/beta ratio is an indicator of hypo-arousal. In turn, this requires further work to elucidate the ratio's functional significance in the disorder. Our brain dynamics studies relating prestimulus EEG amplitude and phase states to ERP outcomes are expected to help in this regard, but we are still at a relatively early stage, currently examining these relationships in control children, in order to better understand normal aspects of brain dynamics before turning to children with AD/HD. This range of studies provides a framework for our recent work relating resting-state EEG anomalies, in individuals with AD/HD, to their symptom profile. This has had promising results, indicating links between increased inattention scores and reduced resting EEG gamma power. With resting-state EEG coherence, reduced left lateralized coherences across several bands have correlated negatively with inattention scores, while reduced frontal interhemispheric coherence has been correlated negatively with hyperactivity/impulsivity scores. Such linkages appear to provide encouraging leads for future EEG research in AD/HD.

Spectral characteristics of the newborn rhesus macaque EEG reflect functional cortical activity

Brain electrical activity is one means of assessing neural development in awake, reactive infants. The development of the electroencephalogram (EEG) in the first week of infant rhesus macaque life is poorly understood though recent work has demonstrated the utility of using this measure to assess neural responses to biologically meaningful stimuli. Here we report on the emergence of EEG rhythms in one-week-old infant rhesus macaques under both light and dark conditions. Our data show that the 5-7Hz frequency band responds reliably to changes in illumination. As well, we found EEG in higher frequencies (12-20Hz) that significantly increase between dark and light conditions similar to the increase in the beta band of humans during cognitive tasks. These findings demonstrate similarities between infant human and infant monkey EEG and suggest approaches for future translational research in developmental psychobiology.

EEG characteristics and visual cognitive function of children with attention deficit hyperactivity disorder (ADHD)

Using visual and auditory continuous performance tests (CPT) and EEG, cognitive function and EEG power were investigated in patients with attention deficit hyperactivity disorder (ADHD). CPT and EEG were conducted for 44 ADHD children and 44 healthy controls of comparable age and sex. The EEG power tests include relative power of theta, alpha, and beta, and theta/beta and theta/alpha ratios. ADHD patients showed significantly higher theta relative power, lower beta relative power, and higher theta/beta ratio (p<0.05). ADHD patients showed a significantly lower score of auditory CPT (p<0.05). The EEG power characteristics were correlated significantly with the visual attention function in ADHD children (p<0.01). Higher-order level cognitive dysfunction affects ADHD pathogenesis. Cortical hypoarousal effects on several mechanisms including the fronto-striatal circuitry may be implicated in the inhibition of prepotent and premature responses.

Narrow band quantitative and multivariate electroencephalogram analysis of peri-adolescent period

Background

The peri-adolescent period is a crucial developmental moment of transition from childhood to emergent adulthood. The present report analyses the differences in Power Spectrum (PS) of the Electroencephalogram (EEG) between late childhood (24 children between 8 and 13 years old) and young adulthood (24 young adults between 18 and 23 years old).

Results

The narrow band analysis of the Electroencephalogram was computed in the frequency range of 0–20 Hz. The analysis of mean and variance suggested that six frequency ranges presented a different rate of maturation at these ages, namely: low delta, delta-theta, low alpha, high alpha, low beta and high beta. For most of these bands the maturation seems to occur later in anterior sites than posterior sites. Correlational analysis showed a lower pattern of correlation between different frequencies in children than in young adults, suggesting a certain asynchrony in the maturation of different rhythms. The topographical analysis revealed similar topographies of the different rhythms in children and young adults. Principal Component Analysis (PCA) demonstrated the same internal structure for the Electroencephalogram of both age groups. Principal Component Analysis allowed to separate four subcomponents in the alpha range. All these subcomponents peaked at a lower frequency in children than in young adults.

Conclusions

The present approaches complement and solve some of the incertitudes when the classical brain broad rhythm analysis is applied. Children have a higher absolute power than young adults for frequency ranges between 0-20 Hz, the correlation of Power Spectrum (PS) with age and the variance age comparison showed that there are six ranges of frequencies that can distinguish the level of EEG maturation in children and adults. The establishment of maturational order of different frequencies and its possible maturational interdependence would require a complete series including all the different ages.

Developmental trajectories of resting EEG power: an endophenotype of autism spectrum disorder

Current research suggests that autism spectrum disorder (ASD) is characterized by asynchronous neural oscillations. However, it is unclear whether changes in neural oscillations represent an index of the disorder or are shared more broadly among both affected and unaffected family members. Additionally, it remains unclear how early these differences emerge in development and whether they remain constant or change over time. In this study we examined developmental trajectories in spectral power in infants at high- or low-risk for ASD. Spectral power was extracted from resting EEG recorded over frontal regions of the scalp when infants were 6, 9, 12, 18 and 24 months of age. We used multilevel modeling to assess change over time between risk groups in the delta, theta, low alpha, high alpha, beta, and gamma frequency bands. The results indicated that across all bands, spectral power was lower in high-risk infants as compared to low-risk infants at 6-months of age. Furthermore high-risk infants showed different trajectories of change in spectral power in the subsequent developmental window indicating that not only are the patterns of change different, but that group differences are dynamic within the first two years of life. These findings remained the same after removing data from a subset of participants who displayed ASD related behaviors at 24 or 36 months. These differences in the nature of the trajectories of EEG power represent important endophenotypes of ASD.

Brain oscillatory complexity across the life span

OBJECTIVE

Considering the increasing use of complexity estimates in neuropsychiatric populations, a normative study is critical to define the 'normal' behaviour of brain oscillatory complexity across the life span.

METHOD

This study examines changes in resting-state magnetoencephalogram (MEG) complexity - quantified with the Lempel-Ziv complexity (LZC) algorithm - due to age and gender in a large sample of 222 (100 males/122 females) healthy participants with ages ranging from 7 to 84 years.

RESULTS

A significant quadratic (curvilinear) relationship (p<0.05) between age and complexity was found, with LZC maxima being reached by the sixth decade of life. Once that peak was crossed, complexity values slowly decreased until late senescence. Females exhibited higher LZC values than males, with significant differences in the anterior, central and posterior regions (p<0.05).

CONCLUSIONS

These results suggest that the evolution of brain oscillatory complexity across the life span might be considered a new illustration of a 'normal' physiological rhythm.

SIGNIFICANCE

Previous and forthcoming clinical studies using complexity estimates might be interpreted from a more complete and dynamical perspective. Pathologies not only cause an 'abnormal' increase or decrease of complexity values but they actually 'break' the 'normal' pattern of oscillatory complexity evolution as a function of age.

EEG from a single-channel dry-sensor recording device

While a laboratory setting and research-grade electroencephalogram (EEG) equipment allow control of variables and high-quality multiple-channel EEG recording, there are situations and populations for which this is not suitable. The present studies examined the validity of a new method of single-channel EEG measurement that is portable and uses dry-sensor technology. In study 1, EEG was recorded simultaneously from the portable device and 4 standard EEG electrodes from a research system, during eyes open (EO) and eyes closed (EC) resting conditions, with 20 adult participants. Average correlations with the research system frequency spectra were highest at site F3 for portable device data processed onboard of the device (r = .90), and for device data processed in a standard manner (r = .89). Further, predictable variations in EO versus EC comparisons were observed. In study 2, twenty-three healthy children had EEGs recorded from the portable device during EO and EC resting conditions, and 3 EO active conditions (ie, relaxation, attention, and cognitive load). Absolute and relative EEG band power differed between conditions in predicted ways, including a reduction in relative theta power and an increase in relative alpha power in EC compared to EO resting conditions. Overall, the results suggest that, while limited in terms of scalp recording locations, the portable device has potential utility in certain EEG recording situations where ease of use is a priority.

Developmental changes in the sleep electroencephalogram of adolescent boys and girls

The sleep electroencephalogram (EEG) changes across adolescence; however, there are conflicting data as to whether EEG changes are regionally specific, are evident in non-rapid eye movement (NREM) and rapid eye movement (REM) sleep, and whether there are sex differences. The present study seeks to resolve some of these issues in a combined cross-sectional and longitudinal analysis of sleep EEG in adolescents. Thirty-three healthy adolescents (18 boys, 15 girls; 11-14 years) were studied on two occasions 6-8 months apart. Cross-sectional analysis of data from the initial visit revealed significantly less slow-wave sleep, delta (0.3 to <4 Hz) and theta (4 to <8 Hz) power in both NREM and REM sleep with advancing age. The age-delta power relationship was significant at the occipital site, with age accounting for 26% of the variance. Longitudinal analysis revealed that NREM delta power declined significantly from the initial to follow-up visit, in association with declining delta amplitude and incidence (P < 0.01), with the effect being greatest at the occipital site. REM delta power also declined over time in association with reduced amplitude (P < 0.01). There were longitudinal reductions in theta, alpha and sigma power in NREM and REM sleep evident at the occipital site at follow-up (P < 0.01). No sex differences were apparent in the pattern of change with age for NREM or REM sleep. Declines in sleep EEG spectral power occur across adolescence in both boys and girls, particularly in the occipital derivation, and are not state-specific, occurring in both NREM and REM sleep.