Effects of methylphenidate in children with attention deficit hyperactivity disorder: a comparison of event-related potentials between medication responders and non-responders.

Event-related potentials (ERPs) were compared among three groups, each with 13 subjects: (1) ADHD non-responders to methylphenidate treatment; (2) ADHD responders to methylphenidate treatment; and (3) normal control children. Response to methylphenidate was determined through extensive psychoeducational and cognitive assessments during a 4-week double-blind medication assessment. ERPs were recorded each week from 13 active electrodes during a visual feature detection task and a semantic classification task. Significant group effects were found for N2 and P3b latencies due to longer latencies for the ADHD children. Off medication, there were no differences between responders and non-responders. However, on methylphenidate non-responders had significantly longer P3b latencies than responders. Cognitive testing also revealed differential performance on medication between non-responders and responders on the paired-associate learning (PAL) task. Thus, both cognitive and ERP measures were found to differentiate ADHD non-responders and responders to methylphenidate treatment.