Another function relevant to OCD that relies on efficient function of the sensorimotor circuit is habit formation. Habits are rigid, largely non-conscious and automatic behaviors that are performed regardless of motivation and outcome (Table 2) [12]. The formation and execution of habits is mediated by motor portions of the sensorimotor circuit (putamen and premotor/motor cortex) [88–89]. In OCD, it has been proposed that compulsions may reflect maladaptive sensorimotor circuit-mediated habitual behaviors that, over time, become decoupled from the initial obsessive thoughts [12, 90]. Consistent with this hypothesis, some patients report habit-like compulsive behaviors. The patient in Case vignette 4 (Table 1), for example, reports a checking ritual that was initially associated with obsessive beliefs about harm. With multiple repetitions over time, her obsessive worries became less important and her checking compulsions became more automatic and were performed to relieve feelings of incompleteness. This subjective feeling could be the result of changes in the stimulus-response associations produced by the excessive repetitions involving the checking behavior. Thus, over the years, increased sensorimotor circuit activity involved in habit-formation may have played a role
