20 Hemispheric Functioning in Children With Subtypes of Attention-Deficit/Hyperactivity Disorder Mei Hsin Suzanne Rolfe University of Auckland, New Zealand Markus Hausmann Ruhr-University Bochum, Germany Karen E. Waldie University of Auckland, New Zealand Objective: The authors investigated line bisection performance in children with Attention-Deficit/Hyperactivity Disorder (AD/HD) subtypes. Previous research with neurotypical children found a rightward bias with right-hand use and a leftward bias with left-hand use; however, research with AD/HD participants has failed to similarly measure the effects of hand use, which was the focus of this study. Method: Line bisection was used to measure differences in right hemisphere function- ing in children (7 to 12 years) with AD/HD-I and AD/HD-C. Results: Initial AD/HD group findings (without subtype dif- ferentiation) replicated previous research. However, further subtype analyses showed that the ADHD-I and ADHD-C groups perform significantly differently. Specifically, the ADHD-I group showed a leftward bias, irrespective of hand use, and the ADHD-C group showed a rightward bias, irrespective of hand use. Conclusion: These findings suggest that the subtypes represent two distinct disorders and that, unlike ADHD-C, ADHD-I may not be the result of right hemisphere dysfunction. (J. of Att. Dis. 2006;10(1)20-27) Keywords: line bisection; ADHD-I; ADHD-C; hand use; frontostriatal Introduction Attention-Deficit/Hyperactivity Disorder (AD/HD) is a neurodevelopmental disorder characterized by three main features—inattention, hyperactivity, and impulsiv- ity (American Psychiatric Association, 2000)—and is often accompanied by behavioral, emotional, or learning problems (R.T. Brown et al., 2001). AD/HD affects between 4% and 12% of the general population of 6- to 12-year-olds (R.T. Brown et al., 2001), and between 30% and 60% of children who develop AD/HD will continue to display symptoms in adulthood (Mannuzza, Klein, & Moulton, 2003). The Diagnostic and Statistical Manual of Mental Disorders (4th ed., text revised; DSM-IV-TR) includes descriptions of three subtypes of AD/HD; ADHD- Combined Type (ADHD-C), ADHD-Predominantly Inattentive Type (ADHD-I), and ADHD-Hyperactive- Impulsive Type (American Psychiatric Association, 2000). However, recent imaging and behavioral studies indicate that the disorder may more accurately include two sub- types: ADHD-C (incorporating both the ADHD-C and ADHD-Hyperactive-Impulsive subgroups) and ADHD-I. For example, using magnetic resonance imaging (MRI), Farmer (2002) reported that children with ADHD-I had smaller right parietal and bilateral dorsolateral region vol- umes and a larger brainstem area and children with ADHD-C had a smaller left parietal and right dorsolateral region when compared with healthy control children. Functionally, ADHD-C participants performed more poorly on the Wisconsin Card Sorting Test (WCST) than ADHD-I participants. The WCST is believed to be a mea- sure of the ability to shift response set, monitor perfor- mance, and respond to feedback (Grodzinsky & Diamond, Journal of Attention Disorders Volume 10 Number 1 August 2006 20-27 © 2006 Sage Publications 10.1177/1087054705286053 http://jad.sagepub.com hosted at http://online.sagepub.com Authors’ Note: Address correspondence to Mei Hsin Suzanne Rolfe, Department of Psychology, University of Auckland, Private Bag 92019, Auckland, New Zealand; s.rolfe@auckland.ac.nz. Articles