Abnormal processing of task-irrelevant stimulus features in adult attention-deficit/hyperactivity disorder (ADHD)

Confirming the hypotheses of "dual process" neuropsychological models of ADHD and recent findings of dissociable cognitive impairments in both top-down and bottom-up processing in ADHD, we found significant group differences both in executive control and in energetic factors subserving the maintainence of baseline performance. Despite abnormally slower reaction times and decreased accuracy in nearly all analyses of both experimental data sets, ADHD group performance was particularly impaired on both tasks when task demands required the execution of cognitive control over task-irrelavant stimulus features. However, supporting the interpretation that deficits in executive control may be, at least partially, caused by bottom-up state dysregulation, ADHD subjects’ difficulties in updating task-set in the task switching paradigm were only evident as a function of an elongated preparation period for an upcoming task. Future experimental neurocognitive research of ADHD employing executive tasks including manipulations directly targeting the allocation of energetic resources (e.g. event rate manipulation) will bring clarity as to which circuits within fronto-striato-thalamo-frontal loops are disrupted in the disorder