Event rate and event-related potentials in ADHD.
BACKGROUND
It has been repeatedly found that performance of children with attention deficit hyperactivity disorder (ADHD) is more impaired when a long inter-stimulus interval (ISI) is used than when a short ISI is used. According to the cognitive-energetic model, this may reflect difficulty in remaining in an optimal motor activation state because of insufficient effort allocation.


METHODS
Event-related potentials (ERPs) were evaluated during a Go/No-Go task that incorporates a condition with a fast and a slow presentation rate.


RESULTS
ADHD, whether or not comorbid with oppositional defiant/conduct disorder (ODD/CD), was associated with a steeper increase in reaction time (RT) from the fast to the slow condition accompanied by a missing increment of the parietal P3. Speed of responding was found to be correlated with P3 amplitude. In the fast condition, children with ADHD made more errors of commission, accompanied by a smaller No-Go N2, a component thought to be related to inhibition; however, after controlling for ODD/CD these differences disappeared.


CONCLUSIONS
The association between the steeper increase in RT and reduced parietal P3s may indicate that the children with ADHD did not allocate enough extra effort to adjust to a potentially under-activated state. However, the event rate effects could not account for all of the differences between groups and also early automatic information processing stages seem disturbed in this disorder as indexed by larger P2 amplitudes. Alternative explanations are discussed.
Wiersema
Roeljan
R
Department of Experimental-Clinical and Health Psychology, Ghent University, Belgium. Roeljan.Wiersema@UGent.be
van der Meere
Jaap
J
Roeyers
Herbert
H
Van Coster
Rudy
R
Baeyens
Dieter
D
D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology*; D019958:Attention Deficit and Disruptive Behavior Disorders / Q000453:epidemiology; D002648:Child; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D010296:Parietal Lobe / Q000503:physiopathology; D010468:Perceptual Disorders / Q000453:epidemiology / Q000503:physiopathology; D015995:Prevalence; D011930:Reaction Time / Q000502:physiology; D013997:Time Factors; D013998:Time Perception / Q000502:physiology