The Effects of Concentrative Meditation on the Electroencephalogram in Novice Meditators.

Following investigations into the benefits of meditation on psychological health and well-being, research is now seeking to understand the mechanisms underlying these outcomes. This study aimed to identify natural alpha and theta frequency components during eyes-closed resting and concentrative meditation states and examined their differences within and between two testing sessions. Novice meditators had their EEG recorded during eyes-closed resting and concentrative meditation conditions, before and after engaging in a brief daily concentrative meditation practice for approximately one-month. Separate frequency Principal Components Analyses (f-PCA) yielded four spectral components of interest, congruent between both conditions and sessions: Delta-Theta-Alpha, Low Alpha, High Alpha, and Alpha-Beta. While all four components showed some increase in the meditation condition at the second session, only Low Alpha (∼9.5-10.0 Hz) showed similar increases while resting. These findings support the use of f-PCA as a novel method of data analysis in the investigation of psychophysiological states in meditation.

Age-related changes in the EEG in an eyes-open condition: II. Subtypes of AD/HD.

This study investigated age-related changes in the EEG of subtypes of Attention-Deficit/Hyperactivity Disorder (AD/HD) compared with neurotypical controls, using an eyes-open resting condition. Two hundred and twenty five children between the ages of 5 and 16 years participated in this study. Groups consisted of AD/HD of the combined (AD/HDcom) and inattentive (AD/HDin) types, which were compared with controls for each of three age ranges: Young (5-8 years), Middle (9-12 years), and Old (13-16 years). The EEG was recorded and analyzed using AMLAB hardware and software, and Fourier transformed to provide estimates for total power, and absolute and relative power in the delta, theta, alpha and beta bands. Compared to controls, the AD/HD groups had globally increased relative theta. Regional differences were found for absolute and relative alpha and beta. Compared to AD/HDcom, AD/HDin had globally reduced total power, absolute and relative theta, and absolute alpha. Regional differences only were found for absolute and relative delta, absolute beta, and relative alpha. No simple interactions were found for diagnostic factors with age. These results indicate that maturational effects can be observed between subtypes of AD/HD and controls in the eyes-open condition with similarities to those reported in eyes-closed conditions, although substantial differences are apparent in the maturation of fast wave activity, primarily alpha. These results provide evidence of maturational differences between subtypes of AD/HD in eyes-open conditions, and provide additional support for the suggestion that subtypes of AD/HD differ in severity rather than the nature of underlying neurological impairment.

Age-related changes in the EEG in an eyes-open condition: I. Normal development.

This study investigated age related changes in the EEG of normal children in an eyes-open condition, in order to provide developmental norms for the study of children and adolescents with Attention-Deficit/Hyperactivity Disorder (AD/HD) - see our companion paper (Mason et al., submitted). EEG was recorded at 17 sites from 75 children (63 boys and 12 girls, in the approximately 5:1 ratio common in AD/HD) between the ages of 5 and 16 years. They comprised three groups, each of 25 children (21 boys and 4 girls), divided into Young (5-8 years), Middle (9-12 years), and Old (13-16 years). The EEG was recorded during an eyes-open resting condition and Fourier transformed to provide estimates for total power, and absolute and relative power in the delta, theta, alpha and beta bands. Total power and absolute delta, theta, alpha, and beta decreased with increasing age, as did relative delta, while relative alpha increased with increasing age. Changes occurred faster in the posterior regions for total power, absolute theta and alpha, relative theta, and in frontal regions for absolute and relative beta. Some lateral developmental effects differed with band. These results indicate that maturation effects observed in the eyes-open EEG show some similarities to those reported in eyes-closed conditions, although substantial differences are apparent in the maturation of fast wave activity, particularly alpha. The data provide simple age-norms for eyes-open investigations of EEG differences in young clinical groups, particularly AD/HD. They encourage further investigations of the activational effects of this simple eyes-closed/eyes-open manipulation, which may aid understanding of the energetics of behaviour.

DSM-5 Adult Attention-Deficit/Hyperactivity Disorder: Sex Differences in EEG Activity.

This study examined sex differences in the EEG of adults diagnosed with Attention-Deficit/Hyperactivity Disorder (AD/HD) according to DSM-5 criteria. Sixteen females and 16 males with AD/HD, and age- and sex-matched control groups, had an eyes-closed resting EEG recorded from 19 electrode sites. EEGs were Fast Fourier transformed and estimates for total power, absolute and relative power in the delta, theta, alpha, beta and gamma bands, and the theta/beta ratio, were analysed across nine cortical regions. Males with AD/HD, compared with male controls, had globally reduced absolute beta, globally elevated relative theta, and a larger theta/beta ratio. In contrast, no global effects emerged between females with and without AD/HD. Significant group interactions indicated that globally elevated relative theta and elevated frontal-midline theta/beta ratio noted in males with AD/HD differed significantly from results in females. There are statistically significant EEG differences in relative theta and the theta/beta ratio between males and females with and without AD/HD. These results indicate that AD/HD affects the EEG activity of males and females differently. This study helps confirm the need for further independent examination of AD/HD within female populations.

Resting state EEG power research in Attention-Deficit/Hyperactivity Disorder: A review update.

This article reviews the eyes-open and eyes-closed resting electroencephalogram (EEG) literature for Attention-Deficit/Hyperactivity Disorder (AD/HD) from 2002 to 2019. This time has seen substantial increase in interest in resting state EEG, with investigations moving from a comparison of an AD/HD sample to a control group, to research investigating a wide range of theoretical and clinical aspects of the disorder. This has included investigations of subgroups based on their EEG profile, sex differences in the EEG, increasing interest in the EEG of adults, and the effects of comorbid disorders on the EEG of people with AD/HD. Research has further investigated the hyper- and hypo- arousal models of AD/HD, as well as the developmental deviation model. From a clinical perspective, a growing body of literature is emerging trying to ascertain if the EEG can be used as a diagnostic test, particularly the theta/beta ratio. While these advances have been made, there is widespread use of both the eyes-open and eyes-closed resting paradigms as being interchangeable, despite the two paradigms differ on a number of important factors. There is also lack of independent replication within the literature, which is needed to consolidate many of the findings that have been published.

Preferred EEG brain states at stimulus onset in normal ageing: Explorations in a fixed interstimulus interval Go/NoGo task.

Some 40 years ago, Erol Basar began an interesting line of brain dynamics research on the phase of oscillatory EEG activity. Stimuli presented at a fixed interstimulus interval (ISI) were reported to produce a "preferred phase angle" at stimulus onset in the ongoing EEG oscillations, so that cortical negativity occurred more often than expected. Our previous work has confirmed this phenomenon in young adults, and linked it to enhancements in stimulus-elicited ERP components and behaviour. The present study sought evidence for this phenomenon in older adults. Twenty healthy independent-living participants (5 males) aged 59.8 to 74.8 years (M = 68.2) completed a fixed ISI equiprobable auditory oddball task. EEG phases in four traditional bands were computed separately for each artefact-free Go and NoGo trial. These were used to group accepted trials according to the phase quartile at stimulus onset in each band, forming 16 mean ERPs for each participant at each phase quartile/band combination, separately for Go and NoGo. The 32 mean ERPs were decomposed by separate Principal Component Analyses, and the N1 and P3 components were examined as a function of EEG phase at stimulus onset in each band. Differential preferential occurrence of phase states was found in all bands, generally confirming prior results in young adults despite important age differences in both EEG spectra and ERP morphology. Substantial effects on N1 and P3 components, as well as prestimulus CNVs, are discussed. The stability of this phenomenon across age indicates its important role in perception and cognition.

Natural alpha frequency components in resting EEG and their relation to arousal.

OBJECTIVE: Global EEG alpha activity is negatively correlated with skin conductance level (SCL), supporting alpha as an inverse marker of arousal. Frequency Principal Components Analysis (f-PCA) of resting EEG amplitude spectra has demonstrated natural components in the alpha band of healthy persons. This is a preliminary exploration of whether such components differ with arousal, possibly underpinning the anomalous ADHD hypoarousal link to reduced alpha. METHOD: Twenty-seven right-handed undergraduate students participated in three 2 minute blocks of resting eyes-open/closed EEG and SCL: EO1, EC, EO2. For each condition, mean EEG spectra were submitted to separate f-PCAs. RESULTS: The inverse alpha/SCL relationship was confirmed for band amplitudes. EO had two alpha components; both correlated negatively with SCL. EC alpha contained four components, but only one had a substantial negative correlation with SCL; two had no relationship, suggesting natural alpha components with different non-arousal functionality in EC. CONCLUSION: Some alpha components in both EC and EO reflect arousal, with other non-arousal components in EC. Our f-PCA approach offers insight into previously-noted alpha anomalies in disorders such as ADHD. SIGNIFICANCE: This proof of concept demonstration in typical participants may provide the basis for a new research effort in clinical disorders involving atypical arousal patterns.

The Theta/Beta Ratio as an Index of Cognitive Processing in Adults With the Combined Type of Attention Deficit Hyperactivity Disorder.

An elevated theta/beta ratio in the EEG has long been observed among individuals with Attention Deficit Hyperactivity Disorder (ADHD). The theta/beta ratio was previously hypothesised to be an index of arousal, but a number of studies failed to find any association between the ratio and indices of arousal, instead proposing that the theta/beta ratio may actually be indicative of cognitive processing. This hypothesis was tested by Clarke et al using a sample of healthy adults, with results indicating that the theta/beta ratio correlated with a marker of cognitive processing (P300 latency in an auditory oddball task), while P300 amplitude correlated with an arousal marker (alpha power). The aim of this study was to test whether similar results could be found in a sample of 41 adults with the combined type of ADHD. EEGs were recorded during an eyes-closed resting condition and an auditory oddball task. Results demonstrated that the theta/beta ratio correlated significantly with P300 latency. Absolute alpha power did not correlate significantly with P300 amplitude or P300 latency. These results support the hypotheses that the theta/beta ratio is a marker of cognitive processing capacity in both the general population and in participants with ADHD, and that the alpha/arousal linkage is anomalous in ADHD.

EEG development in Attention Deficit Hyperactivity Disorder: From child to adult.

OBJECTIVE: Attention Deficit Hyperactivity Disorder (ADHD) is one of the most common psychiatric disorders found in children. While an extensive literature has documented the EEG in this clinical population, few studies have investigated EEG throughout the lifespan in ADHD. This study aimed to investigate EEG maturational changes, in subjects with ADHD combined type, that spanned from childhood into adulthood. METHOD: Twenty five male adults with ADHD were assessed between the ages of 8-12 years and again as adults. At both ages, an EEG was recorded during an eyes-closed resting period, and power estimates were calculated for relative delta, theta, alpha and beta. RESULTS: At the childhood assessment, the ADHD subjects had elevated posterior delta. Relative theta was elevated, with diminished alpha activity across all sites. Significant maturational changes were observed, with reductions in the delta and theta bands, and increases in the alpha and beta bands across all electrodes. In adulthood, relative to controls, diminished frontal delta and elevated global theta activity were apparent. CONCLUSIONS: Substantial developmental changes occurred in the EEG of these subjects. These results identify important issues when using EEG as part of the diagnosis for ADHD. SIGNIFICANCE: This study is the first to explore EEG changes from childhood to adulthood over an 11 year period in the same subjects with ADHD.

The EEG Theta/Beta Ratio: A marker of Arousal or Cognitive Processing Capacity?

Attention-Deficit/Hyperactivity Disorder (AD/HD) is the most common psychiatric disorder of childhood and has been extensively researched using EEG technology. Within this literature, one of the most widely examined measures has been the theta/beta ratio. The theta/beta ratio was initially hypothesised to represent the arousal mechanism. However, subsequent research has shown this to be inaccurate and it was hypothesised that the ratio represents cognitive processing capacity. To examine that hypothesis, this study aimed to test the relationship between the P300 and the theta/beta ratio. The P300, absolute alpha and the theta/beta ratio were measured at Fz, Cz and Pz, and correlated in a group of 47 normal adults. A significant positive correlation was found between P300 latency and the theta/beta ratio. No relationship was found between P300 amplitude and the theta/beta ratio. P300 amplitude, but not latency, significantly correlated with alpha power. These results support the hypothesis that the theta/beta ratio is a marker of cognitive processing capacity.

Time Effects on Resting EEG in Children With/Without AD/HD.

In this study we extend on behavioural evidence to examine the effect of time on EEG measures related to arousal and emotion/motivation in children with/without AD/HD. Thirty children with AD/HD and 30 age- and sex-matched controls participated. EEG was recorded during an eyes-closed resting condition and divided into three 2.5 min blocks after pre-processing. Time effects for absolute and relative alpha activity were found in healthy controls; these effects did not interact with AD/HD status. Interactions between time and AD/HD status were found for absolute theta, relative theta, and theta/beta ratio (TBR), with these EEG indices increasing over time in children with AD/HD. Moreover, IQ played a role in the interaction between time and AD/HD status. These results are consistent with predictions from both the optimal stimulation model and the delay aversion model, and suggest important methodological considerations for future EEG research in children with/without AD/HD.

Atypical interference control in children with AD/HD with elevated theta/beta ratio.

The theta/beta ratio (TBR) is a major area of interest within electroencephalogram (EEG) research in AD/HD. While researchers suggest a prognostic role for TBR in AD/HD, its relationship to behavior remains uncertain. Recent evidence suggests that elevated TBR in AD/HD may be related to atypical inhibition, particularly at an attentional level. This study aimed to examine the performance on three inhibitory tasks of children with AD/HD. Fifty-eight children with AD/HD participated, divided into an elevated TBR (ET) group and a control group (CT). A behavioral disassociation was found - compared to CT, ET showed more difficulty in inhibiting surrounding stimuli but had less day-to-day inhibitory issues measured by BRIEF. There was no significant group difference on response inhibition. The results support the prognostic value of TBR in AD/HD. Elevated TBR may be an inhibitory biomarker; further studies are needed to explore the behavioral implications in patients without elevated TBR.

An Investigation of Stimulant Effects on the EEG of Children With Attention-Deficit/Hyperactivity Disorder.

Stimulant medications are the most commonly prescribed treatment for Attention-Deficit/Hyperactivity Disorder (AD/HD). These medications result in a normalization of the EEG. However, past research has found that complete normalization of the EEG is not always achieved. One reason for this may be that studies have used different medications interchangeably, or groups of subjects on different stimulants. This study investigated whether methylphenidate and dexamphetamine produce different levels of normalization of the EEG in children with AD/HD. Three groups of 20 boys participated in this study. There were 2 groups with a diagnosis of AD/HD; one group, good responders to methylphenidate, and the second, good responders to dexamphetamine. The third group was a normal control group. Baseline EEGs were recorded using an eyes-closed resting condition, and analyzed for total power and relative delta, theta, alpha, and beta. Subjects were placed on a 6-month trial of methylphenidate or dexamphetamine, after which a second EEG was recorded. At baseline, the children with AD/HD had elevated relative theta, less relative alpha and beta compared with controls. Baseline differences were found between the two medication groups, with the dexamphetamine group having greater EEG abnormalities than the methylphenidate group. The results indicate that good responders to methylphenidate and dexamphetamine have different EEG profiles when assessed before medication, and these differences may represent different underlying central nervous system deficits. The 2 medications were found to result in substantial normalization of the EEG, with no significant differences in EEG changes occurring between the 2 medications. This indicates that the degree of pretreatment EEG abnormality was the major factor contributing to the degree of normalization of the EEG. As good responders to the 2 medications appear to have different central nervous system abnormalities, it is recommended that stimulant medications be treated independently and not used interchangeably in research and treatment of AD/HD.

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.

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.

EEG Differences Between the Combined and Inattentive Types of Attention-Deficit/Hyperactivity Disorder in Girls: A Further Investigation.

This study further investigated electroencephalogram (EEG) differences between girls with the Combined and Inattentive types of attention-deficit/hyperactivity disorder (AD/HD). We selected subjects with widely separated scores on hyperactivity-impulsivity symptoms to behaviorally exaggerate diagnostic group differences. Twenty girls with AD/HD Combined type, 20 girls with AD/HD Inattentive type, and 20 controls (aged 7-12 years) had an eyes-closed resting EEG recorded from 19 electrodes. The EEG was fast Fourier transformed, and estimates for total power, absolute and relative power in the delta, theta, alpha, and beta frequency bands, and the theta/beta ratio were calculated and analyzed in 9 scalp regions. Girls of the Combined type, compared with girls of the Inattentive type, had elevated midline total power, elevated temporal absolute alpha activity, elevated posterior absolute beta activity, reduced right hemisphere relative delta and reduced left hemisphere relative alpha activity, and reduced theta/beta ratio in the left hemisphere. Although topographic differences were again found between the AD/HD types, significant global differences remain elusive in the EEGs of girls with the Combined and Inattentive types. Despite creating behaviorally exaggerated AD/HD type groups, girls' EEG activity failed to replicate differences found previously in mixed-sex groups. The EEG profiles of AD/HD types in girls are markedly different from those found in boys. This reinforces the notion that it is no longer appropriate to apply the male-based literature to all AD/HD groups; rather, the use of single-sex subject groups is necessary in EEG research of AD/HD.

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.

Excess beta activity in the EEG of children with attention-deficit/hyperactivity disorder: a disorder of arousal?

Past research has reported that a small proportion of children with attention-deficit/hyperactivity disorder (AD/HD) have excess beta activity in their EEG, rather than the excess theta typical of the syndrome. This atypical group has been tentatively labeled as hyperaroused. The aim of this study was to determine whether these children have a hyperaroused central nervous system. Participants included 104 boys aged 8 to 13 years old, with a diagnosis of either the Combined or Inattentive type of AD/HD (67 combined type), and 67 age-matched male controls. Ten and a half minutes of EEG and skin conductance (SCL) were simultaneously recorded during an eyes-closed resting condition. The EEG was Fourier transformed and estimates of total power, and relative power in the delta, theta, alpha, and beta bands, and the theta/beta ratio, were calculated. AD/HD patients were divided into an excess beta group and a typical excess theta group. Relative to controls, the typical excess theta group had significantly increased frontal total power, theta and theta/beta ratio, with reduced alpha and beta across the scalp. The excess beta group had significantly reduced posterior total power, increased centro-posterior delta, globally reduced alpha, globally increased beta activity, and globally reduced theta/beta ratio. Both AD/HD groups had significantly reduced SCL compared to the control group, but the two groups did not differ from each other on SCL. These results indicate that AD/HD children with excess beta activity are not hyperaroused, and confirm that the theta/beta ratio is not associated with arousal. This is the first study of arousal measures in AD/HD children with excess beta activity, and has implications for existing models of AD/HD.

Sex differences between the combined and inattentive types of attention-deficit/hyperactivity disorder: an EEG perspective.

This study investigated sex differences between the EEGs of Combined and Inattentive types of attention-deficit/hyperactivity disorder (AD/HD) within boys and girls aged 8-12 years. Subject groups included 80 AD/HD Combined type (40 boys and 40 girls), 80 AD/HD Inattentive type (40 boys and 40 girls) and 80 controls (40 boys and 40 girls). An eyes-closed resting EEG was recorded and Fourier transformed to provide estimates for absolute and relative power in the delta, theta, alpha and beta frequency bands, as well as total power and the theta/beta ratio. The boy AD/HD groups, compared with boy controls, had greater absolute and relative theta, greater theta/beta ratio, reduced absolute and relative alpha, and reduced absolute and relative beta. The girl AD/HD groups, compared with girl controls, had greater absolute delta, greater absolute and relative theta, greater theta/beta ratio, greater total power, and reduced relative delta and relative beta. Between AD/HD types, Combined type boys had globally greater absolute and relative theta, greater theta/beta ratio, and less relative alpha than Inattentive type boys. While topographical differences emerged, there were no significant global differences between AD/HD types in girls. That is, EEG differences between AD/HD types are dissimilar in boys and girls. Different EEG maturational patterns between boys and girls also obscure AD/HD-related EEG abnormalities. These results have important implications for our understanding of AD/HD in girls. Ignoring such sex differences may have compromised the value of previous AD/HD investigations, and these sex differences should be recognised in future research.