Symposium overview Attention deficit/hyperactivity disorder: characteristics, interventions, and models Merle G. Paule a, *, Andrew S. Rowland b , Sherry A. Ferguson a , John J. Chelonis c , Rosemary Tannock d , James M. Swanson e , F. Xavier Castellanos f a Behavioral Toxicology Laboratory, Division of Neurotoxicology, HFT-132, National Center for Toxicological Research, 3900 NCTR Road, Jefferson, AR 72079 - 9502, USA b Epidemiology Branch, NIEHS, A3- 05, P.O. Box 12233, Research Triangle Park, NC 27709- 2233, USA c Department of Psychology, University of Arkansas at Little Rock, 2801 South University Avenue, Little Rock, AR 72204, USA d Brain and Behaviour Research Programme (Psychiatry Research), The Research Institute of the Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8 e Child Development Center, University of California at Irvine, 19722 MacArthur Boulevard, Irvine, CA 92612, USA f Child Psychiatry Branch, National Institute of Mental Health, Room 3B - 19, 10 Center Drive, Bethesda, MD 20892 - 1251, USA Received 28 April 2000; accepted 30 May 2000 Abstract An epidemiological study of Attention Deficit / Hyperactivity Disorder (ADHD) suggests that the prevalence may be two to three times higher than the figure of 3± 5% often cited. In addition, the data suggest that both underdiagnosis and overdiagnosis occur frequently. Rodent animal models of ADHD, like the Spontaneously Hypertensive Rat (SHR) and other rat models such as those with chemical and radiation - induced brain lesions and cerebellar stunting, and the Coloboma mouse model exhibit clear similarities with several aspects of the human disorder and should prove useful in studying specific traits. Operant behavioral tasks that model learning, short - term memory and simple discriminations are sensitive to ADHD and methylphenidate has been shown to normalize ADHD performance in a short - term memory task. Recent findings challenge not only the current postulate that response inhibition is a unique deficit in ADHD, but also the concepts of ADHD and its treatment, which presume intact perceptual abilities. Time perception deficits may account, in part, for the excessive variability in motor response times on speeded reaction time tasks, motor control problems and motor clumsiness associated with ADHD. The Multimodality Treatment Study of ADHD (MTA) provided data suggesting that pharmacological interventions that included systematic and frequent follow - up with parents and teachers, with or without psychosocial interventions, are superior to psychosocial interventions or standard community care alone. Additionally, the MTA was one of the first studies to demonstrate benefits of multimodal and pharmacological interventions lasting longer than 1 year. Imaging studies have demonstrated differences in brain areas in children with ADHD: anterior corpus callosum, right anterior white matter, and cerebellar volumes are all decreased in children with ADHD and there is less brain asymmetry in ADHD subjects. Additionally, functional imaging studies, coupled with pharmacological manipulations, suggest decreased blood flow and energy utilization in prefrontal cortex and striatum, and the dysregulation of catecholamine systems in persons with ADHD. D 2000 Elsevier Science Inc. All rights reserved. Keywords: Attention deficit disorder; Epidemiology; Prevalence; Rodent models; Cerebellar stunting; Short -term memory; Cognitive markers; Treatment; Stimulant medication; Multimodal interventions; Neuroimaging; Prefrontal cortex; Dopaminergic dysfunction 1. Introduction At the 1999 Annual Meeting of the Neurobehavioral Teratology Society held in Keystone, CO, a series of presentations that focused on Attention Deficit / Hyperac- tivity Disorder (ADHD) were presented. The following text summarizes these six presentations and includes a biblio- graphy that should serve as an important resource for all of those interested in this topic. Dr. Andy Rowland from the National Institute of Environmental Health Sciences opened the symposium with an overview of the epidemio- logy of ADHD. * Corresponding author. Tel.: + 1 - 870 - 543 - 7147 / 7203; fax: + 1 - 870 - 543 - 7720. E-mail address: mpaule@nctr.fda.gov (M.G. Paule). 0892-0362/00/$ ± see front matter D 2000 Elsevier Science Inc. All rights reserved. PII:S0892-0362(00)00095-7 Neurotoxicology and Teratology 22 (2000) 631± 651