Dis-regulation of response inhibition in adult Attention Deficit Hyperactivity Disorder (ADHD): an ERP study.

Objective: To define the brain activity involved in impaired response inhibition of Attention Deficit Hyperactivity Disorder (ADHD) in adults.

Methods: Performance measures and brain activity of 14 adult ADHD subjects and 14 controls, matched for age, gender, and overall intelligence were compared in an auditory Go-NoGo paradigm to tones. The task required a button press (Go) to 80% and inhibition of response (NoGo) to 20% of the tones, according to the tone's pitch.

Results: In NoGo trials ADHD subjects made significantly more commission errors compared to controls. ERPs of ADHD subjects showed smaller amplitudes of P3 (but not N2), and longer latencies of both N2 and P3. Source current density estimation revealed reduced activity in the right frontal dorsolateral cortex and in the posterior cingulate of the ADHD group. In addition, ADHD subjects showed an unexpected significantly enhanced response inhibition in Go trials, with excessive omission errors associated with significantly larger N2 amplitudes.

Conclusions: In ADHD the neural networks sub-serving response inhibition are impaired. Conclusions: ADHD is a general dis-regulation of behavioral inhibition, not limited to response inhibition.