Franca E. Dupuy

Behavioural differences between EEG-defined subgroups of children with Attention-Deficit/Hyperactivity Disorder

OBJECTIVE This study investigated the presence and nature of EEG clusters within a clinically-referred sample of children with Attention-Deficit/Hyperactivity Disorder (AD/HD), and whether behavioural differences exist between clusters. METHOD Participants were 155 boys with AD/HD and 109 age- and gender-matched controls. EEG was recorded during an eyes-closed resting condition and Fourier transformed to provide estimates for total power, and relative delta, theta, alpha, and beta. EEG data were grouped into 3 regions, and subjected to Cluster Analysis. Behavioural data for each cluster were compared against the remaining AD/HD subjects. RESULTS Four EEG clusters were found. These were characterised by (a) elevated beta activity, (b) elevated theta with deficiencies of alpha and beta, (c) elevated slow wave with less fast wave activity, and (d) elevated alpha. An exploratory analysis of behavioural correlates with these EEG subtypes indicated the presence of interesting trends that need further investigation. CONCLUSIONS This study found that the AD/HD EEG profiles reported in past studies are robust and not substantially affected by the inclusion of children with other comorbid conditions. The observed group differences in behavioural profiles indicated that different patterns of EEG activity have importance in determining behaviour. SIGNIFICANCE This is the first study to link behavioural profiles of children with AD/HD to specific EEG abnormalities.

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.

Childhood EEG as a predictor of adult attention-deficit/hyperactivity disorder.

OBJECTIVE The aim of this study was to determine whether EEG differences exist between children with attention-deficit/hyperactivity disorder (AD/HD) who later outgrow the disorder and those who continue to be symptomatic as adults. METHODS Thirty-eight boys, diagnosed with AD/HD as children, were reassessed 11 years later to determine who met criteria for adult AD/HD. At the childhood assessment, an EEG was recorded from the AD/HD group and a control group, during an eyes-closed resting condition. This was analysed for absolute and relative power in the delta, theta, alpha and beta bands, and the theta/beta ratio. RESULTS At the childhood assessment, the AD/HD group had an EEG profile typical of the disorder, with increased absolute and relative theta, reduced relative alpha, and increased theta/beta ratio. EEG differences were found between those who outgrew the disorder and those who did not - the adult AD/HD group had greater childhood global relative beta, reduced frontal relative theta, and increased frontal absolute and relative beta. CONCLUSIONS These results suggest the existence of specific CNS differences in childhood AD/HD that may be used to predict the developmental course of the disorder. SIGNIFICANCE This is the first study to investigate childhood EEG markers of adult AD/HD.

Girls with attention-deficit/hyperactivity disorder: EEG differences between DSM-IV types.

This study investigated EEG differences between the Combined and Inattentive types of Attention-Deficit/Hyperactivity Disorder (AD/HD) in girls. Thirty girls with AD/HD of the Combined type, 30 girls with the Inattentive type, and 30 controls (aged 8–12 years) had a resting eyes-closed EEG recorded from 21 electrodes. The EEG was Fast Fourier Transformed and estimates for total power, and absolute and relative power in the delta, theta, alpha and beta frequency bands, were analyzed in nine cortical regions. Across the scalp, girls with AD/HD had elevated total power, elevated absolute delta and theta, reduced relative delta and beta, and increased relative theta compared with controls. Compared with the Inattentive group, the Combined group had greater right hemisphere absolute theta and greater midline posterior absolute beta activity. The Combined group also had reduced right hemisphere relative delta, greater left hemisphere relative theta, reduced midline posterior relative alpha and reduced central relative beta activity. In conclusion, girls with AD/HD had increased slow wave (delta and theta) activity and reduced beta activity, which are robust results in the predominantly-male AD/HD literature, and exhibited the elevated theta/beta abnormality. The lack of global differences between DSM-IV AD/HD types differs from previous studies of boys and mixed-sex groups. The present results highlight the homogeneity of EEG profiles in AD/HD girls, which could be due to sex-bias in the diagnostic criteria. This study is the first to investigate EEG differences between the Inattentive and Combined types of AD/HD with a purely female sample.

EEG coherence in children with attention-deficit/hyperactivity disorder: Differences between good and poor responders to methylphenidate

This retrospective study investigated differences in regional derivations of EEG coherence between good and poor responders to methylphenidate (MPH) in children (aged 8-12 years) with the combined type of attention-deficit/hyperactivity disorder (AD/HD). Participants included groups of good and poor male MPH responders and an aged-matched group of male controls. An eyes-closed, resting electroencephalogram (EEG) was recorded from 21 electrode sites. Coherence was calculated from eight intrahemispheric and eight interhemispheric electrode pairs, for the delta, theta, alpha and beta frequency bands. Compared with controls, the AD/HD participants had enhanced laterality over short-medium inter-electrode distances, and elevated frontal interhemispheric coherences, in the theta band. Good MPH responders had higher intrahemispheric coherences than poor MPH responders over short-medium and long inter-electrode distances in the beta band. Enhanced laterality at short-medium inter-electrode distances suggests that the AD/HD children may have a developmental lag in short-axonal connections in the left hemisphere. Elevated frontal interhemispheric theta coherence consistently indicates some frontal dysfunction in AD/HD. The beta coherence differences found between good and poor MPH responders could indicate that good MPH responders have some type of structural dysfunction associated with cortical connections involved in attention/arousal.

EEG coherence in girls with Attention-Deficit/Hyperactivity Disorder: Stimulant effects in good responders

This study investigated the effects of stimulants on EEG coherence in girls with Attention-Deficit/Hyperactivity Disorder (AD/HD). Twenty girls with AD/HD (aged 7-12) and 20 age- and sex-matched controls had an eyes-closed resting electroencephalogram (EEG) recorded from 21 electrode sites. Coherence was calculated from eight intrahemispheric electrode pairs (four in each hemisphere), and eight interhemispheric electrode pairs, for the delta, theta, alpha and beta frequency bands. AD/HD participants were tested twice: first, prior to medication being prescribed, and second, six months later on a therapeutic dose of a stimulant. With intrahemispheric coherences at short-medium inter-electrode distances, AD/HD girls off-medication had reduced lateralisation in the delta, theta and alpha bands. They also had reduced lateralisation in the theta band for longer inter-electrode distances, and increased frontal interhemispheric coherences in all frequency bands. Medication had no impact on the laterality anomalies, but produced novel increases in intrahemispheric coherences at short-medium inter-electrode distances, which reached significance in the delta band and approached significance in the alpha band. However, these increased coherences remained indistinguishable from control levels. Reduced hemispheric lateralisations found in these AD/HD participants illustrate cortical abnormalities consistent with maturational lag explanations. The widespread elevated frontal interhemispheric coherences found in these AD/HD girls could reflect the narrow profile of female medication responders identified in clinical settings. The lack of substantial coherence medication effects in good clinical responders supports a previous medication study with AD/HD boys, and suggests that these coherence anomalies reflect structural, rather than solely functional, differences in brain development in 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.

Caffeine effects on resting-state electrodermal levels in AD/HD suggest an anomalous arousal mechanism.

The effect of a single oral dose of caffeine was examined in a randomised double-blind placebo-controlled repeated-measures cross-over study. Eighteen children with AD/HD, aged between 8 and 13 years, were individually age- and gender-matched with a control group. All children participated in two sessions, one week apart. Skin conductance level (SCL) from a 3 min eyes-closed epoch, commencing 30 min after ingestion of caffeine or placebo, was examined. Across conditions, mean SCL was lower in the AD/HD group than controls, confirming hypoarousal in AD/HD. Caffeine produced an increase in SCL, and this increase did not differ between the groups. However, arousal increases were dose-dependent in controls, but not in AD/HD. Rather, caffeine-induced arousal increases in the AD/HD group were positively related to their hyperactivity/impulsivity levels. This suggests an anomalous arousal mechanism in AD/HD functionally related to impairment in one symptom dimension.

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.

EEG and electrodermal activity in girls with Attention-Deficit/Hyperactivity Disorder

OBJECTIVE This study investigated the Hypoarousal Model of Attention-Deficit/Hyperactivity Disorder (AD/HD) in girls. METHODS 40 girls with AD/HD and 40 girl controls (aged 7-12 years) had an eyes-closed resting EEG recorded from 19 electrodes and Fourier transformed. Estimates for total power, absolute and relative power in the delta, theta, alpha, beta and gamma frequency bands, and theta/beta ratio were analysed in nine cortical regions. Skin conductance level (SCL) was simultaneously recorded. Regression analyses explored relationships between symptoms and physiology. RESULTS Compared with controls, girls with AD/HD had globally elevated relative delta, globally reduced absolute beta, and globally reduced absolute and relative gamma activity. Girls with AD/HD also had lower mean SCL. Inattentive symptoms were predicted by elevated frontal relative delta, reduced SCL, and reduced temporal relative gamma activity, while elevated hyperactive-impulsive symptoms correlated with elevated frontal relative delta activity in both the patient and control groups. CONCLUSIONS These EEG results are comparable with the limited female AD/HD literature. Girls with AD/HD are hypoaroused, indicated by reduced SCL, and appear to have an anomalous arousal mechanism. Absolute and relative gamma results are similar to previous findings in AD/HD children. Symptom correlations with physiology offer intriguing insights for future research. SIGNIFICANCE This is the first study to examine CNS arousal exclusively in girls with AD/HD.