Publications (66) View all
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Article: Excess beta activity in the EEG of children with Attention-Deficit/Hyperactivity Disorder: A disorder of arousal?
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ABSTRACT: 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.International journal of psychophysiology: official journal of the International Organization of Psychophysiology 04/2013; · 3.05 Impact Factor -
Article: Sex differences between the Combined and Inattentive types of Attention-Deficit/Hyperactivity Disorder: An EEG perspective.
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ABSTRACT: 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 8-12years. Subject groups included 80AD/HD Combined type (40 boys and 40 girls), 80AD/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.International journal of psychophysiology: official journal of the International Organization of Psychophysiology 04/2013; · 3.05 Impact Factor -
Article: Event Related Potentials in Two DSM-IV Subtypes of Attention-Deficit/Hyperactivity Disorder: An Investigation Using a Combined Modality Auditory/Visual Oddball Task.
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ABSTRACT: This study investigated whether event-related potentials (ERPs) from an inter-modal oddball task could distinguish between children with Attention-Deficit Hyperactivity Disorder (AD/HD) of the combined type (AD/HDcom) and controls, and between children with AD/HD of the predominantly inattentive type (AD/HDin) and controls. Three age-matched groups of 8-12 year old boys (25 controls, 25 AD/HDcom and 25 AD/HDin) were presented with an inter-modal oddball task in which a counter-phasing checkerboard was the non-target visual stimulus (randomly presented on 80% of trials), and a 2000 Hz tone was the auditory target (20% of trials). Stimuli were presented at a fixed rate (every 1.03 s) and participants were required to silently count all targets. The task successfully differentiated both the AD/HDcom and AD/HDin children from controls. Both AD/HD groups showed reduced P2 and P3 amplitudes compared with controls, a common deficit independent of stimulus modality/significance. Compared with controls. AD/HDcom boys showed greater component equipotentiality and increased component latencies than the AD/HDin boys in their auditory target ERPs. A similar but weaker pattern of greater component equipotentiality and increased component latencies for the visual non-target ERPs was found only in AD/HDin boys. These results were interpreted as indicating both a general AD/HD deficit and separate deficits unique to each DSM-IV subtype. (PsycINFO Database Record (c) 2012 APA, all rights reserved)10/2012; -
Article: Arousal and Activation in a Continuous Performance Task: An Exploration of State Effects in Normal Children.
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ABSTRACT: The concepts of arousal and activation have had a confused history in Psychophysiology, and there is no widely accepted consensus on their usefulness in the field. This study aimed to explore whether these concepts could be separated in terms of their effects on the phasic Orienting Response (OR) and behavioral performance. We defined arousal at a particular time to be the energetic state at that time, reflected in electrodermal activity and measured by skin conductance level. Task-related activation was defined as the change in arousal from a resting baseline to the task situation. A continuous performance task was used with normal children. The magnitude of the mean phasic OR elicited by target stimuli was dependent on arousal, but not on task-related activation. Two performance measures (mean reaction time and number of errors) improved with increasing activation, but not with arousal. These data suggest the value of conceptualizing arousal and activation as separable aspects of the energetics of physiological and behavioral responding in future studies of attention, cognition, and emotion. (PsycINFO Database Record (c) 2012 APA, all rights reserved)Journal of Psychophysiology 10/2012; 19(2):91-99. · 1.54 Impact Factor -
Article: Caffeine effects on resting-state electrodermal levels in AD/HD suggest an anomalous arousal mechanism.
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ABSTRACT: 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.Biological psychology 01/2012; 89(3):606-8. · 4.36 Impact Factor
