Stimulus context and motor preparation in attention-deficit/hyperactivity disorder

Aim: To investigate (1) whether and how local stimulus context variation may modify behavioural and preparatory motor processes in children, and (2) if these effects differ between healthy children and children with attention-deficit/hyperactivity disorder (ADHD) aged 9-12 years. Methods: Behavioural parameters and contingent negative variation (CNV) at conical motor electrodes were recorded during a cued continuous performance task (AX-CPT) in three stimulus context conditions (Go, NoGo, neutral). Stimulus context was varied on the basis of stimulus types preceding the cue letter A. Results: In all children, responses were slowed in both the NoGo- and Go-conditions relative to the neutral condition. Stimulus context affected preparatory motor processes in both groups but differentially. ADHD children showed smaller CNV potentials and a functionally irrelevant over-activation of the ipsilateral motor area. Conclusions: Local stimulus context may modify behavioural and preparatory motor processes in children. In ADHD, local context variations may disrupt behaviour due to inefficient regulation of supervisory higher control systems. (C) 2007 Elsevier B.V. All rights reserved.