EEG coherence in girls with Attention-Deficit/Hyperactivity Disorder: Stimulant effects in good responders Franca E. Dupuy a , Adam R. Clarke a, ⁎, Robert J. Barry a , Rory McCarthy b , Mark Selikowitz b a Brain & Behaviour Research Institute and School of Psychology, University of Wollongong, Wollongong 2522, Australia b Sydney Developmental Clinic, 6/30 Carrington St., Sydney 2000, Australia abstract article info Article history: Received 26 February 2008 Received in revised form 28 May 2008 Accepted 21 July 2008 Available online 25 July 2008 Keywords: AD/HD Girls EEG Coherence Stimulants Medication 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 interhemi- spheric 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. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Attention-Deficit/Hyperactivity Disorder (AD/HD) is a debilitating and persistent childhood condition, characterised by symptoms of inattention, hyperactivity and impulsivity and affects between 4% and 6% of school-aged children (American Psychiatric Association, 1994; Pelham et al., 1992). Without appropriate treatment, AD/HD can interrupt normal childhood development and functioning, and often persists into adulthood (Barkley, 1997b; Mannuzza et al., 1993). Prevalence rates indicate that AD/HD is more common in boys than girls (American Psychiatric Association, 1994; James and Taylor, 1990; Pelham et al., 1992; Sawyer et al., 2001; Volkow and Swanson, 2003). Clinical samples have reported ratios of boys to girls as high as 9:1, while epidemiological studies have found 4:1 ratios (American Psychiatric Association, 1994; Gaub and Carlson, 1997). The high prevalence in boys has resulted in AD/HD research predominantly focusing on males. However, the literature developed from this research cannot always directly transfer to females with the same disorder. Compared to boys, girls with AD/HD are more likely to show symptoms of inattention, hyper-talkativeness and high emotional reactivity, rather than physical hyperactivity (Gaub and Carlson, 1997; Quinn, 2005). As hyper-talkativeness and emotional reactivity (symptoms often found in girls) are not currently listed in the DSM- IV diagnostic criteria (American Psychiatric Association, 1994), girls who display these behaviours may not be identified or referred for treatment. This may help explain the ratio discrepancies between clinical and epidemiological prevalence estimates (Gaub and Carlson, 1997; Quinn, 2005). For this reason, it is important for AD/HD research to investigate girls and boys separately. 1.1. Coherence Electroencephalogram (EEG) coherence measures the similarity in cortical electrical activity between two electrode sites (Lubar et al., 1999) and has been conceptualised as the correlation in the time domain between two signals in a given frequency band (Shaw, 1981). Coherence provides information about the degree of connectivity between structures underlying a pair of recording electrodes (Clarke International Journal of Psychophysiology 70 (2008) 151–157 ⁎ Corresponding author. Tel.: +61 2 4221 5775; fax: +61 2 4221 4163. E-mail address: adam_clarke@uow.edu.au (A.R. Clarke). 0167-8760/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.ijpsycho.2008.07.012 Contents lists available at ScienceDirect International Journal of Psychophysiology journal homepage: www.elsevier.com/locate/ijpsycho