ERP indices of working memory updating in AD/HD: differential aspects of development, subtype and medication.

Keage HAD Clark CR, Hermens DF, Williams LM, Kohn MR,Clarke S, Lamb C, Crewther D, Gordon E (in press). ERP indices of working memory updating in AD/HD: differential aspects of development, subtype and medication, Journal of Clinical Neurophysiology, , -.



This study investigated whether children and adolescents diagnosed with the Predominantly Inattentive and Combined subtypes of Attention Deficit/Hyperactivity Disorder (AD/HD-in and AD/HD-com respectively) differed on psychophysiological indices of working memory updating off- and on-stimulant medication, as compared to controls and each other. ERPs were recorded in AD/HD and control participants during a one-back working memory task. The N100 (discrimination), P150 (selection), N300 (memory retrieval) and P450wm (updating) components following non-target stimuli, that served to update working memory with target identity, were assessed. Pre-medication abnormalities were obtained for the N300 component, delayed in the child AD/HD-com group and attenuated in the adolescent AD/HD in group; and P450wm component for all AD/HD groups, expressed as either delayed latency and/or attenuated amplitude. ERP abnormalities were predominantly ameliorated following stimulant medication. There were no psychophysiological differences between the subtypes. A general feature of the disorder relates to a deficit in the conscious updating of working memory systems with newly relevant information (P450wm), which varies with age and subtype. Children with AD/HD-com and adolescents with AD/HD-in also exhibit abnormalities in the retrieval of relevant prior memories (N300). This study indicates that AD/HD is related to abnormalities in the capacity to modulate the content of working memory stores..