The ventral cognitive circuit includes prefrontal and striatal regions involved in self-regulatory behaviors (Figure 4) [16]. One ventral cognitive function that has been proposed as fundamentally involved in OCD is response inhibition, which is the ability to withhold inappropriate behaviors. Response inhibition is mediated in part by the inferior frontal gyrus (IFG) and the subthalamic nucleus (STN) (Table 2) [16, 119], although other regions beyond the ventral cognitive circuit, such as the inferior parietal lobule and insula, are also involved [120]. The persistence of maladaptive, repetitive thoughts and behaviors in OCD, despite awareness that these are excessive, unreasonable and have negative consequences, is suggestive of impairment inhibition. Such deficits might explain (partly at least) both the expression of obsessions and the consequent compulsive behaviors. For instance, the patient in Case vignette 4 (Table 1) describes an excessive checking ritual that she feels driven to perform (despite consciously knowing it is excessive) before leaving the office at the end of the work day, which is tied to her obsessive belief that something bad might happen (an electrical short circuit might cause
