Accepted

Objectives: We investigated the involvement of the basal ganglia in inhibiting ongoing responses in patients with Parkinson’s disease (PD). Methods: Thirty two patients with PD and 31 orthopaedic controls performed the stop signal task, which allows an estimation of the time it takes to inhibit an ongoing reaction (stop signal reaction time, SSRT). Results: Patients with PD showed significantly longer SSRTs than the controls. This effect seemed to be independent of global cognitive impairment and severity of PD. Furthermore, in the PD patients, there was no significant relation between general slowing and inhibitory efficiency. Conclusions: Our results provide evidence for involvement of the basal ganglia in the inhibition of ongoing responses. P revious lesion and neuroimaging studies have shown that the frontal lobes, especially the (right) inferior frontal gyrus and the anterior cingulate gyrus, play an important role in response inhibition.1–6 Deficits in response inhibition have also been demonstrated after lesions of th