The effect of methylphenidate on response inhibition and the event-related potential of children with Attention Deficit/Hyperactivity Disorder

• Published in: International journal of psychophysiology 2005-10, Vol.58 (1), p.47-58
• Main Authors: Broyd, Samantha J., Johnstone, Stuart J., Barry, Robert J., Clarke, Adam R., McCarthy, Rory, Selikowitz, Mark, Lawrence, Carlie A.
• Format: Article
• Language: English
• Subjects: AD/HD; Adolescent; Age Factors; Attention Deficit Disorder with Hyperactivity - drug therapy; Attention Deficit Disorder with Hyperactivity - physiopathology; Central Nervous System Stimulants - administration & dosage; Child; Event-related potential; Evoked Potentials, Auditory - drug effects; Galvanic Skin Response - drug effects; Humans; Inhibition; Male; Methylphenidate; Methylphenidate - administration & dosage; Neural Inhibition - drug effects; Reaction Time - drug effects; Skin conductance level
• ISSN: 0167-8760; 1872-7697
• DOI: 10.1016/j.ijpsycho.2005.03.008

Children with Attention Deficit/Hyperactivity Disorder (AD/HD) appear to be deficient in inhibitory processes, as reflected in behavioural and electrophysiological measures. This study examined the effect of methylphenidate (MPH) on response inhibition in children with AD/HD. Event-related potentials (ERPs) and skin conductance level (SCL) were recorded from 18 boys with AD/HD and 18 controls while they performed a cued Go/Nogo task with 70% Go probability. All participants performed the task twice, with an hour interval between test sessions. At the beginning of this interval children with AD/HD took their normal morning dose of MPH. The AD/HD group showed lower SCL than controls pre-medication, a difference not found subsequent to the administration of MPH. While the AD/HD group made more overall errors (omission + commission) pre-medication, and continued to make more omission errors than controls post-medication, the groups became comparable on the number of commission errors, suggesting MPH ameliorates deficits in response inhibition. Children with AD/HD displayed enhanced N1 and P2 amplitudes, and reduced N2 amplitudes relative to controls. These differences were not significant post-medication, at least partly attributable to the action of MPH. This study is unusual in the concurrent examination of electrodermal and electrophysiological measures of medication effects in children with AD/HD, with the retesting of both the AD/HD and control groups allowing a more valid estimate of the effects of medication, rather than assuming that retesting does not have a substantial impact.