A differential neural response in obsessive-compulsive disorder patients with washing compared with checking symptoms to disgust

Background. Patients with obsessive-compulsive disorder (OCD) have symptoms that predominantly concern washing (washers) or checking (checkers), or bo th. Functional neuroimaging has been used to identify the neural correlates of the urge to ritualize but has not distinguished between washing and che cking symptoms in OCD. We used functional magnetic resonance imaging to com pare the neural response to emotive pictures in washers and checkers. Methods. In one of two 5-minute experiments, washers (N = 7), checkers (N = 7) and age-matched normal controls (N = 14) were scanned while viewing alt ernating blocks of normally disgusting (rated as disgusting by all subjects ) and neutral pictures. In the other experiment, all patients and a normal subgroup (N = 8) viewed alternating blocks of washer-relevant (rated as mor e disgusting by washers than normal controls or checkers) and neutral pictu res. Results. In all subjects, normally disgusting pictures activated visual reg ions implicated in perception of aversive stimuli and the insula, important in disgust perception. Only in washers were similar regions activated by w asher-relevant pictures. In checkers, these pictures activated frontostriat al regions associated with the urge to ritualize in OCD. Normal controls we re more similar in neural response to checkers than washers to these pictur es. Both normal controls and checkers had frontal regions activated signifi cantly more by washer-relevant than normally disgusting pictures, and had t hese regions activated significantly more than washers by washer-relevant p ictures. Conclusions. We demonstrate a differential neural response to washer-releva nt disgust in washers and checkers: only washers demonstrate a neural respo nse to washer-relevant disgust associated with emotion perception rather th an attention to non-emotive visual detail.