Resting-state EEG gamma activity in children with Attention-Deficit/Hyperactivity Disorder

Objective

Children with Attention-Deficit/Hyperactivity Disorder (AD/HD) have well-described abnormalities in the four traditional EEG bands. However, to date the gamma band has not been widely investigated. This study investigated resting-state EEG in children with AD/HD and matched controls, with a particular focus on gamma activity.

Method

Forty children with AD/HD, and 40 age- and sex-matched controls, participated. EEG was recorded from 19 sites during an eyes-closed resting condition and Fourier transformed to provide estimates for absolute and relative power in the delta, theta, alpha, beta and gamma bands.

Results

Children with AD/HD had elevated levels of absolute delta and theta power, and decreased levels of absolute beta and gamma power, compared to controls. With relative power measures, children with AD/HD showed enhanced delta and theta activity, with reduced alpha, beta and gamma activity. Inattention scores on the Conners’ Parent Rating Scale were negatively correlated with absolute gamma.

Conclusions

These patients demonstrate the typical EEG profile in the eyes-closed resting state, over the delta, theta, alpha and beta bands, associated with AD/HD. In addition, compared with controls, they demonstrate reduced absolute and relative gamma activity. These differences appear to contribute importantly to their dysfunctional stimulus processing, and impact their behavioural outcomes.

Significance

This resting-state study extends the well-established fast-wave EEG deficits in children with AD/HD to the gamma band, and links that to increased inattention, which is of special importance in understanding their cognitive-processing problems.     

Effects of stimulant medications on the EEG of girls with Attention-Deficit/Hyperactivity Disorder

OBJECTIVE: Stimulant medications are the most commonly used treatments for Attention-Deficit/Hyperactivity Disorder (AD/HD) in North America and Australia, although it is still not entirely known how these medications work. This study investigated the effects of stimulant medications on the EEG of girls with AD/HD. METHODS: An initial EEG was recorded during an eyes-closed resting condition. Data from 19 electrode sites were Fourier transformed to provide absolute and relative power estimates for the delta, theta, alpha and beta bands. The data were then averaged into 9 regions and an analysis of both global and regional differences was performed. Subjects were placed on a six-month trial of a stimulant and a second EEG was recorded at the end of the trial. RESULTS: The unmedicated girls had significantly greater total power, absolute delta and theta, more relative theta especially in the frontal regions, and reduced frontal relative delta and beta activity compared with controls. Medication resulted in normalisation of theta power, but after medication, increased relative beta was also apparent in the AD/HD group. CONCLUSIONS: These results indicate that stimulant medications result in a normalisation of slow wave activity in the EEG. In line with published research on the effects of arousal on the EEG, these results suggest that stimulant medications may have their therapeutic effect by improving the EEG substrate of processing deficits in these children. However, this requires further testing during active processing tasks. SIGNIFICANCE: This is the first study to investigate the effect of stimulant medications on the EEG of girls with AD/HD.     

Correlation Between EEG Activity and Behavior in Children with Attention-Deficit/Hyperactivity Disorder

The aim of this study was to determine whether EEG activity in specific bands correlated with the core behavioral symptoms of children with attention-deficit/hyperactivity disorder (AD/HD). Sixty boys diagnosed with AD/HD Combined type and 60 age-matched male controls participated in this study. An EEG was recorded during an eyes-closed resting condition and relative power estimates in the delta, theta, alpha, and beta bands, and the theta/beta ratio, were calculated. The EEG measures of the AD/HD group were converted to z scores relative to the controls, and these were correlated with scores on the Conners' Rating Scale obtained from a parent. The AD/HD group had global increases in theta activity and the theta/beta ratio, increased frontal delta, with reduced global alpha and frontal beta activity. Frontal theta activity correlated with inattention, the theta/beta ratio correlated with hyperactivity-impulsivity, and both measures correlated with a Combined type diagnosis. EEG power anomalies in AD/HD are associated with specific symptom clusters in the disorder.     

EEG abnormalities in adolescent males with AD/HD.

OBJECTIVE: This study investigated EEG abnormalities in adolescents with attention-deficit/hyperactivity disorder (AD/HD). METHODS: Fifteen AD/HD subjects and 15 control subjects participated in this study. All subjects were between 14 and 17 years of age. The EEG was recorded from 19 electrode sites and was analysed to provide estimates of both absolute and relative power in the delta, theta, alpha and beta bands. Theta/alpha and theta/beta ratio coefficients were also calculated. RESULTS: Across the scalp, AD/HD subjects were characterised by greater absolute delta and theta activity, and an increased theta/beta ratio compared to controls. No group differences were found for either absolute or relative alpha, or absolute beta. However, AD/HD subjects demonstrated a reduction in relative beta activity in the posterior regions. CONCLUSIONS: The AD/HD group showed significant deviations from normal CNS development, in particular in posterior regions. This supports previous suggestions that individuals with an EEG profile that is not indicative of a maturational lag are more likely to have AD/HD during adolescence. SIGNIFICANCE: This is the first study to investigate EEG abnormalities in adolescents with AD/HD during an eyes-closed resting condition.     

EEG Activity in Subtypes of Attention-Deficit/Hyperactivity Disorder

ABSTRACT

This article is a review of electroencephalography (EEG) studies of different types and subtypes of Attention-Deficit/Hyperactivity Disorder (AD/HD). The review outlines the definitional history of AD/HD, and changes that have been made to the conceptualization of the disorder as these different definitions have impacted on the EEG literature. EEG studies are examined using various models of AD/HD based on either behaviour or underlying central nervous system (CNS) abnormalities. From these studies, it appears that AD/HD children generally have increased absolute and relative power in the theta band, either at the frontal electrode sites or over the entire scalp. Reductions in absolute and relative power in the alpha and beta bands have also been found in several studies, although relative power measures appear to be more reliable than absolute power. Increased delta activity in both absolute and relative power has also been noted in several studies. These results are discussed in terms of existing CNS-based models of AD/HD, which attribute the disorder to hypoarousal or a maturational lag in CNS development. Implications of these data for clinical use and future research and development in AD/HD are considered.     

Age and gender effects in EEG coherence: III. Girls with attention-deficit/hyperactivity disorder.

OBJECTIVE: This study investigated intrahemispheric and interhemispheric EEG coherences as a function of age in girls with different DSM-IV subtypes of Attention-Deficit/Hyperactivity Disorder (AD/HD). It completes a series of 3 studies aimed at clarifying developmental and gender impacts on the coupling between brain regions in this disorder. METHODS: Three groups of 40 children (AD/HD combined type, AD/HD inattentive type, and normal controls) participated. Each group contained 8 females in each of 5, 1-year age bands from 8 to 12 years. EEG was recorded from 21 sites during an eyes-closed resting condition. Wave-shape coherence was calculated for 8 intrahemispheric electrode pairs (4 in each hemisphere), and 8 interhemispheric electrode pairs, within each of the delta, theta, alpha and beta bands. RESULTS: Developmental effects in intrahemispheric coherences at shorter and longer inter-electrode distances were not as predicted by Thatcher's two-compartment model, contrary to previous findings in boys. Females with AD/HD showed evidence of developmental delay and widespread anomalous elevations in coherence. Girls with AD/HD of the combined type showed similar but greater anomalies than girls with AD/HD of the inattentive type. CONCLUSIONS: Girls with AD/HD show coherence anomalies relative to age- and gender-matched controls, which differ substantially from those shown by boys with AD/HD. These coherence anomalies did not differ in nature between girls with different DSM-IV subtypes of AD/HD, suggesting that subtype differences in girls reflect only symptom severity. SIGNIFICANCE: The data reported here indicate qualitative differences in EEG coherences in girls with AD/HD compared with controls, and quantitative differences between girls with different subtypes of AD/HD. Both sets of effects differ in nature from those previously found in boys with AD/HD, showing the need to carefully consider gender in future studies of AD/HD.     

Children with attention-deficit/hyperactivity disorder and autistic features: EEG evidence for comorbid disorders

Attention-deficit/hyperactivity disorder (AD/HD) is the most common psychiatric disorder of childhood, although AD/HD is rarely the only diagnosis given to these children. Within the literature there is some debate as to whether it is valid to diagnose AD/HD with autism as a comorbid disorder, since the present diagnostic systems exclude the diagnosis of both disorders in the same child. The aim of this study was to determine whether electroencephalography (EEG) differences exist between two groups of children diagnosed with AD/HD, one scoring high (AD/HD+) and one scoring low (AD/HD?) on a measure of autism. The EEG was recorded during an eyes-closed resting condition from 19 electrodes, and Fourier transformed to provide absolute and relative power estimates in delta, theta, alpha and beta bands. Compared to age- and sex-matched controls, the AD/HD? group had increased absolute power in all frequency bands, somewhat higher relative theta activity and decreased relative delta. In comparison to the AD/HD? group, patients with autistic features (AD/HD+) had a number of qualitative differences in the beta and theta bands. These results indicate the presence of two comorbid conditions in the AD/HD+ group, which suggests that AD/HD and autism can occur in the same individual.     

EEG differences in children as a function of resting-state arousal level.

OBJECTIVE: This study aimed to explore the basis of a theoretical position which has major impact in the current literature on attention-deficit/hyperactivity disorder (AD/HD) - that the ratio of theta to beta power in the EEG (the theta/beta ratio) represents central nervous system (CNS) arousal. METHODS: Resting state topographic EEG activity was investigated as a function of CNS arousal in normal right-handed boys. Arousal was defined in terms of electrodermal activity, which has a long history in Psychology as a measure of CNS arousal. RESULTS: Relative delta, theta, and beta power, and the theta/beta ratio, failed to differ significantly between age-matched groups which differed markedly in skin conductance level and non-specific electrodermal fluctuations. The high-arousal group showed significantly lower levels of relative alpha power, particularly in posterior and hemispheric regions, with higher alpha frequencies in these areas. CONCLUSIONS: These data fail to support the theoretical linkage between the theta/beta ratio and CNS arousal. Further work is needed to disentangle the different correlates of arousal and task-related activation, particularly in cognitive and attentional-processing terms. SIGNIFICANCE: The outcomes of this study, in addition to clarifying the nature of EEG markers of CNS arousal, have important implications for our understanding of AD/HD, as they require re-evaluation of current models of the disorder.     

A review of electrophysiology in attention-deficit/hyperactivity disorder: I. Qualitative and quantitative electroencephalography.

OBJECTIVE: This article reviews the electroencephalography (EEG) literature in relation to attention-deficit/hyperactivity disorder (AD/HD). METHODS: The review briefly outlines the history of the disorder, focusing on the changing diagnostic systems which both reflect and constrain research into AD/HD. Both qualitative and quantitative EEG studies are examined, and their results are discussed in relation to various models of AD/HD. Implications of these data for future research and development in AD/HD are considered. RESULTS: In terms of resting EEG, elevated relative theta power, and reduced relative alpha and beta, together with elevated theta/alpha and theta/beta ratios, are most reliably associated with AD/HD. Theta/alpha and theta/beta ratios also discriminate diagnostic subgroups of AD/HD. Recent studies of EEG heterogeneity in this disorder indicate the existence of different profiles of cortical anomalies which may cut across diagnostic types. CONCLUSIONS: The research to date has identified a substantial number of EEG correlates of AD/HD which hold promise for improving our understanding of the brain dysfunction(s) underlying the disorder. Further work in this field may benefit from a broader conceptual approach, integrating EEG and other measures of brain function.     

Quantitative EEG in low-IQ children with attention-deficit/hyperactivity disorder.

OBJECTIVE: This study investigated EEG differences between children with attention-deficit/hyperactivity disorder (AD/HD) and matched control subjects, with either normal or low IQs. METHODS: Twenty normal-IQ and 20 low-IQ children with AD/HD, and 40 age-, IQ- and sex-matched control subjects participated in this study. EEG was recorded from 21 sites during an eyes-closed resting condition and Fourier transformed to provide estimates for total power, and absolute and relative power in the delta, theta, alpha and beta bands. RESULTS: Children with AD/HD had increased theta activity with decreased levels of alpha and beta activity compared to control subjects. IQ was not found to impact on the EEG. No significant differences were found between subjects with normal and low IQs, with the low- and high-IQ AD/HD groups having similar EEG profiles. CONCLUSIONS: Low-IQ children with AD/HD have similar EEG abnormalities to those with normal IQs, and IQ does not appear to impact on EEG power measures. SIGNIFICANCE: This is the first study to investigate EEG differences in low-IQ children with and without AD/HD.     

Quantitative EEG in schizophrenia and in response to acute and chronic clozapine treatment

Topographic quantitative electroencephalographic (EEG) power and frequency indices were collected in 17 treatment refractory, DSM-III diagnosed schizophrenic patients, before and after acute (single dose) and chronic (six weeks) clozapine treatment, as well as in 17 healthy volunteers. Prior to treatment, patients exhibited greater overall absolute theta power, slower mean alpha frequency and elevated absolute delta and total power in anterior regions. Acute dosing increased total spectrum power globally, slow wave power posteriorally, mean alpha frequency and beta power anteriorally and decreased alpha power posteriorally. Six weeks of clozapine treatment significantly reduced clinical ratings of positive and negative symptoms as well as symptoms of global psychopathology. Chronic treatment resulted in EEG slowing as shown by decreases in relative alpha power, mean beta/total spectrum frequency and by widespread increases in absolute total and delta/theta power. The preliminary findings suggest that brain electric profiling may be a promising tool for assessing and understanding the central impact of pharmacotherapeutic interventions in schizophrenia.     

Examining the diagnostic utility of EEG power measures in children with attention deficit/hyperactivity disorder.

OBJECTIVE: This study investigated the diagnostic utility of EEG power during eyes-closed resting conditions for children with attention-deficit/hyperactivity disorder (AD/HD). METHODS: Subjects consisted of 253 boys with AD/HD combined type and 67 age-matched controls. EEG was recorded from 21 sites during an eyes-closed resting condition and was Fourier transformed to provide estimates for total power and absolute and relative power in delta, theta, alpha and beta bands. Factor analysis was used to group sites into frontal, central and posterior regions, with these data subjected to cluster analysis. Logistic regression was performed on the entire AD/HD sample versus control, for AD/HD clusters versus control, and then for each AD/HD cluster independently versus control, using total, absolute and relative power measures. RESULTS: Logistic regression performed on the clusters independently produced the best classification results, with a sensitivity of 89.0% and a specificity of 79.6%, with an overall classification accuracy of 87.0%. CONCLUSIONS: The obtained classification results are supportive of an independent diagnostic test for AD/HD based on EEG power at rest. SIGNIFICANCE: This is the first study to investigate sensitivity and specificity of EEG power for AD/HD in a resting condition.     

Functional EEG connectivity is a neuromarker for adult attention deficit hyperactivity disorder symptoms

ObjectiveAltered brain functional connectivity has been shown in youth with attention-deficit/hyperactivity disorder (ADHD). However, relatively little is known about functional connectivity in adult ADHD, and how it is linked with the heritability of ADHD.MethodsWe measured eyes-open and eyes-closed resting electroencephalography (EEG) from 38 adults with ADHD, 45 1st degree relatives of people with ADHD and 51 healthy controls. Functional connectivity among all scalp channels was calculated using a weighted phase lag index for delta, theta, alpha, beta and gamma frequency bands. A machine learning analysis using penalized linear regression was used to identify if connectivity features (10,080 connectivity pairs) could predict ADHD symptoms. Furthermore, we examined if EEG connectivity could accurately classify participants into ADHD, 1st degree relatives and/or control groups.ResultsHyperactive symptoms were best predicted by eyes-open EEG connectivity in delta, beta and gamma bands. Inattentive symptoms were predicted by eyes-open EEG connectivity in delta, alpha and gamma bands, and eyes-closed EEG connectivity in delta and gamma bands. EEG connectivity features did not reliably classify participants into groups.ConclusionsEEG connectivity may represent a neuromarker for ADHD symptoms.SignificanceEEG connectivity may help elucidate the neural basis of adult ADHD symptoms.     

Changes in absolute power values of EEG spectra in the follow-up of Alzheimer's disease

We have studied the absolute and relative power and amplitude of EEG spectra (T6–02) of 24 patients with "probable" Alzheimer's disease at the early stage of the disease and 1 year later and also compared the values to those of normal elderly controls. A remarkable variability of the absolute values was evident both for the patients and for the controls. The AD patients had significantly higher absolute theta amplitude and power and the absolute beta values tended to decrease compared to controls. Absolute delta and alpha values did not differ from those of the controls. The relative delta, theta and alpha power and amplitude, and beta amplitude showed significant changes in AD patients, whereas the relative beta power was unchanged. In the follow-up of AD patients at 1 year, absolute alpha values decreased and delta values tended to increase. As to relative values, both the alpha and the delta significantly changed but the theta and the beta were unaltered. We conclude that both absolute and relative power and amplitude values should be considered in EEG studies of dementia patients. Absolute values are especially useful in follow-up.     

EEG differences in children between eyes-closed and eyes-open resting conditions

ObjectiveRecent work on arousal vs. activation in adults showed that skin conductance levels (SCLs) increased, and global alpha levels decreased, from eyes-closed to eyes-open resting baseline conditions. This study explored whether similar effects occur in children.MethodsEEG activity was recorded from 30 children aged 8–12 years during counterbalanced eyes-closed and eyes-open resting conditions; SCL was measured as an index of arousal.ResultsSCLs were negatively correlated with mean alpha levels in the eyes-closed condition, and increased significantly from eyes-closed to eyes-open. Reductions were found in across-scalp mean absolute delta, theta, alpha, and beta from eyes-closed to eyes-open. Topographic changes were evident in all bands except alpha.ConclusionsResults confirm the use of mean alpha level as a measure of resting-state arousal under eyes-closed and eyes-open conditions. Focal changes in the other bands suggest that these reflect differences in activation, rather than the simple increase in arousal shown in alpha.SignificanceThis child study confirms the generality of eyes-closed vs. eyes-open non-alpha EEG measures differing in mean power levels and topography, the latter indicating brain activity related to visual processing. Such differences should be considered when evaluating EEG research, and in choosing baseline conditions for different paradigms.     

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

ObjectiveAttention 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.MethodTwenty 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.ResultsAt 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.ConclusionsSubstantial developmental changes occurred in the EEG of these subjects. These results identify important issues when using EEG as part of the diagnosis for ADHD.SignificanceThis study is the first to explore EEG changes from childhood to adulthood over an 11 year period in the same subjects with ADHD.     

Ibuprofen treatment modifies cortical sources of EEG rhythms in mild Alzheimer’s disease

ObjectiveNon-steroidal anti-inflammatory drugs such as ibuprofen have a protective role on risk of Alzheimer’s disease (AD). Here we evaluated the hypothesis that long-term ibuprofen treatment affects cortical sources of resting electroencephalographic (EEG) rhythms in mild AD patients.MethodsTwenty-three AD patients (13 treated AD IBUPROFEN; 10 untreated AD PLACEBO) were enrolled. Resting EEG data were recorded before and 1 year after the ibuprofen/placebo treatment. EEG rhythms were delta (2–4 Hz), theta (4–8 Hz), alpha 1 (8–10.5 Hz), alpha 2 (10.5–13 Hz), beta 1 (13–20 Hz), and beta 2 (20–30 Hz). LORETA was used for EEG source analysis.ResultsIn the AD PLACEBO group, amplitude of delta sources was globally greater at follow-up than baseline. Instead, amplitude of delta sources remained stable or decreased in the majority of the AD IBUPROFEN patients. Clinical (CDR) but not global cognitive status (MMSE) reflected EEG results.ConclusionsThese results suggest that in mild AD patients, a long-term ibuprofen treatment slightly slows down the progressive increment of delta rhythms as a sign of contrast against the neurodegenerative processes.SignificanceThey motivate future investigations with larger population and extended neuropsychological testing, to study the relationships among ibuprofen treatment, delta cortical sources, and higher order functions.     

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

OBJECTIVES: This study investigated age-related changes and sex differences in the EEGs of normal children. METHODS: Forty boys and 40 girls, between the ages of 8 and 12 years, participated in this study. The EEG was recorded during an eyes-closed resting condition and Fourier transformed to provide estimates for total power, absolute and relative power in the delta, theta, alpha and beta bands, and for theta/alpha and theta/beta ratios. RESULTS: Absolute delta activity decreased with age. Relative delta and theta decreased and alpha and beta increased with increasing age. The theta/alpha and theta/beta ratios decreased with increasing age. All of these indicated a developmental reduction in slow wave activity. Maturational differences were found in the rates of change between the midline and the two hemispheres. In the absolute delta and the theta/beta ratio, the midline and the two hemispheres became more equipotential with age. In the beta band, power increased at a greater rate than in the two hemispheres. Sex differences were found, with males having less theta and more alpha than females. CONCLUSIONS: These results indicated that maturation occurs earlier at the midline than in the two hemispheres. Females were also found to have a developmental lag in the EEG compared with males.     

Individual analysis of EEG background-activity within school age: impact of age and sex within a longitudinal data set

Objectives

Quantitative EEG can monitor changes in brain function during development and may help to understand developmental disorders. However, current EEG-databases are primarily based on standardized frequency bands which disregard age-related changes in alpha peak frequency (PF) and therefore complicate the interpretation of spectral estimates in the theta and alpha range.

Methods

We used a two point longitudinal design in order to analyze intraindividual changes in 40 healthy children and adolescents with age (T₁: 6-18 years; interval approximately 4 years). Using a 64-channel eyes closed resting EEG we calculated absolute/relative power in individualized frequency bands (IFB: delta, theta, alpha_1/2 and beta) based on PF.

Results

PF increased with age, with changes being larger for children than adolescents. Controlling for changes in PF, changes in absolute/relative alpha_1/2 power and in absolute beta power were minor. Relative beta power, however, increased while absolute/relative delta and theta power decreased massively.Sex-differences in PF did not reach significance. However, boys exhibited larger changes during adolescence than girls for all absolute power measures except alpha.

Conclusion

Normal EEG development during school-age is mainly based on an absolute decrease of slow frequency activity and increases of PF which may be interpreted in terms of a reorganization of the EEG towards a higher frequency oscillatory scale rather than a maturation of the theta-alpha_1/2 band power sequence. Age-related changes differed between boys and girls suggesting a different developmental timing for the sexes. In future studies a combined analysis of PF and IFB may help to specify deviations in developmental disorders.     

Effects of stimulant medications on children with attention-deficit/hyperactivity disorder and excessive beta activity in their EEG.

OBJECTIVE: This study investigated the effects of stimulant medications on the Electroencephalography (EEG) of children with the combined type of attention-deficit/hyperactivity disorder (ADHD) together with excessive beta activity in their EEG. METHODS: Twenty ADHD and 20 control subjects participated in this study. EEG was recorded from 21 sites during an eyes-closed resting condition and Fourier transformed to provide estimates for total power and absolute and relative power in the delta, theta, alpha and beta bands, and for the theta/alpha and theta/beta ratios. Subjects were placed on a 6-month trial of a stimulant medication and a second EEG was recorded at the end of the trial. RESULTS: The unmedicated ADHD group had greater absolute and relative beta, less absolute and relative alpha, a higher theta/alpha and a lower theta/beta ratio than the control group. In the frontal regions the ADHD group had an increase in total power, absolute theta, absolute and relative beta and the theta/beta ratio, with greater relative delta, relative theta, and absolute and relative alpha in posterior regions. With medication use, absolute beta activity and frontal total power decreased, although these changes represented a reduction in power, not a normalisation. CONCLUSIONS: These results indicate that ADHD children with excessive beta activity in their EEG are probably not hypoaroused as previously suggested, and that beta activity in these children is probably only associated with the impulsivity and/or hyperactivity aspects of the disorder, but may not necessarily be associated with inattention. SIGNIFICANCE: This study is the first to investigate effects of stimulant medications on the EEG of ADHD children with excessive beta activity in their EEG.