Functional neuroimaging studies have repeatedly implicated a circuit comprising ventral parts of the frontal lobe and the basal ganglia in the stop-signal task.24 Neuropsychological studies of brain damaged patients have revealed an important contribution of the right inferior frontal gyrus, in particular, to stop-signal performance.95 In the case of rodent models, lesions of the rodent orbitofrontal cortex,96 but not of the medial prefrontal cortex,96, 97 and the medial,98 but not ventral,97 striatum have been found to slow stop-signal reaction times (Figure 1). It has been proposed that the right inferior frontal gyrus exerts top down influence over striatal regions, possibly via the subthalamic nucleus,99 to mediate response inhibition within the stop-signal task. A very similar pattern of results is found for go/no-go tasks.100–102
