The sensorimotor circuit includes cortical and subcortical regions involved in the generation and control of motor behaviors and integration of sensory information (Figure 3) [16, 72]. Although perhaps the most well-known examples of OCD symptoms involve fear of harmful events with compulsions that resemble reactions to potential threat, a significant proportion of patients (60–70%) also experience sensory phenomena (SP) consisting of aversive or uncomfortable sensations or perceptions that drive repetitive behaviors (Table 2) [73–76]. SP are prevalent in patients with ordering, arranging, counting and repeating compulsions, which are frequently performed until the patient achieves the sensation or perception that things are “just right” (“not-just-right” experiences) [73, 75] or “complete” [77]. These phenomena additionally manifest as tactile sensations of feeling dirty that drive washing and cleaning compulsions, rather than fear of illness or disease [73, 75]. For instance, the patient in Case vignette 3 reports a tactile sensation of having dirty hands, which prompts excessive hand washing (Table 1). Similarly, content analyses have revealed a key theme in the content of contamination obsessions to be sensations of feeling dirty under the
