ERP differences in visual attention processing between attention-deficit hyperactivity disorder and control boys in the absence of performance differences FRINI KARAYANIDIS, a,e PHILIPPE ROBAEY, a MICHELLE BOURASSA, a DAVID DE KONING, d GUY GEOFFROY, b and GILLES PELLETIER c a Cognitive Psychophysiology and Neuropsychiatry Laboratory, Department of Psychiatry, Sainte-Justine Hospital, University of Montreal, Quebec, Canada b Department of Paediatrics, Service of Neurology, Sainte-Justine Hospital, University of Montreal, Quebec, Canada c Department of Psychiatry, Sainte-Justine Hospital, University of Montreal, Quebec, Canada d TALO bv, Bussum, The Netherlands e Department of Psychology, University of Newcastle, New South Wales, Australia Abstract Event-related potentials ~ ERPs! were recorded during a visual two-choice reaction time ~ RT! task in attention-deficit hyperactivity disorder ~ADHD! and control boys selected using strict inclusion and exclusion criteria. No group differences were found in mean RT and correct responses. Although early occipital ERPs were not affected in the ADHD group, the peak latency of early anterior ERPs ~ N1, P1, N2! was significantly delayed. ADHD showed a larger effect of stimulus type on the frontal negativity ~ N530! and the posterior late negativity ~nSW! and a smaller effect of stimulus type on anterior N2 and posterior P3b amplitude. The development of N530 and P450 amplitude across blocks of five trials was analyzed using orthogonal polynomial trend analysis of variance software. In the control group, P450 amplitude to “frequent” stimuli reduced across blocks. In the ADHD group, N530 amplitude increased for “rare” stimuli across blocks. It is suggested that the ADHD group showed a lack of automatization of the categorization process with increasing time on task for which they compensated by controlled attentional processes. Descriptors: Attention-deficit hyperactivity disorder, Event-related potentials, Visual attention, Children Despite increasing precision in the diagnostic criteria used to de- fine attention-deficit hyperactivity disorder ~ADHD! over the past couple of decades, neither the biological basis nor the cognitive mechanisms underlying this condition has been defined success- fully. Many ADHD studies have used event-related potential ~ ERP! recordings to investigate the existence and locus of a deficit at some point across the sensory-motor processing chain ~for review see Klorman, 1991; Levy & Ward, 1995!. Within this framework, ERP methodology is particularly pertinent. ERPs can differentiate between stimulus and response-related processes, early sensory versus later cognitive aspects of stimulus processing, and most importantly, can provide information concerning the time course of processing of both relevant and irrelevant information. Most ERP studies in ADHD have focused largely on the P3b component using continuous performance, oddball, or selective attention tasks. Results have been highly variable. Many studies report that ADHD children show a smaller P3b amplitude com- pared with controls ~e.g., Holcomb, Ackerman, & Dykman, 1985, 1986; Michael, Klorman, Salzman, Borgstedt, & Dainer, 1981!, whereas other studies find no difference in P3b amplitude ~e.g., Novak, Solanto, & Abikoff, 1995; Oades, Dittmann-Balcar, Schep- ker, Eggers, & Zerbin, 1996; Satterfield, Schell, Nicholas, & Backs, 1988!. Klorman ~1991! argued that the decline in P3b amplitude in ADHD occurs only when there is a concomitant decline in behav- ioral performance. However, more recent studies complicate the picture, in some cases showing a decline in P3b amplitude with no decline in behavioral performance ~Johnstone & Barry, 1996! and, in other cases, no effect on P3b despite a significant decline in performance ~ Novak et al., 1995!. Satterfield, Schell, Nicholas, Satterfield, and Freese ~1990! suggested that discrepancies in P3b amplitude findings may be related to the age of the children tested. Specifically, their data showed no or minimal differences in P3b amplitude between ADHD and controls at 6 years of age ~Satter- field et al., 1988, 1990!, but significant differences emerging in the same group of children at age 8 ~Satterfield et al., 1990!. Given that studies vary widely in the age range included, it is possible that differences between studies can be attributed, at least partially, to an interaction between age and ADHD on P3b amplitude. Al- though, in most studies, the decline in P3b amplitude is equally We gratefully acknowledge the support of the National Health Re- search and Development Program ~ NHRDP! from Health and Welfare Canada. This work was supported by a clinician-scientist award ~ FRSQ! to P.R. Special thanks go to Anne Bolduc and Veronique Lacroix for evalua- tion and psychometric testing, Nataly Filion for recruitment of subjects, Phetsamone Vannasing for her highly competent technical assistance dur- ing recordings, Johannes E.A. Stauder for setting up the recording system, and Ge Yong Liang for his help with Figure 3. Finally, we thank the children who participated in the study and their families. Address reprint requests to: Dr. Philippe Robaey, Department of Psy- chiatry, Ste Justine Hospital, 3100 Ellendale, Montreal, Quebec, H3S 1W3 Canada. E-mail: robaey@alize.ERE.Montreal.CA. Psychophysiology, 37 ~2000!, 319–333. Cambridge University Press. Printed in the USA. Copyright © 2000 Society for Psychophysiological Research 319