Two neuroimaging studies [86–87] have directly examined the neural correlates of SP in OCD. Subirà and colleagues [86] reported larger gray matter volumes in a sensorimotor area encompassing postcentral gyrus, the posterior extent of precentral gyrus and paracentral lobule in individuals with OCD and SP (OCD+SP) compared to those with OCD without SP (OCD-SP) and non-psychiatric controls. OCD+SP (but not OCD-SP) had larger volumes of posterior putamen, pallidum, and thalamus than controls. Sensorimotor volume increases were not correlated with SP severity, but group differences remained after controlling for medication and comorbid conditions, including TS. Brown et al. [87] examined neural activity while OCD patients viewed “body-focused” videos (described in Table 2) designed to elicit activation in sensorimotor circuitry. Greater SP severity was correlated with greater activity in mid-posterior insula and, at a lower statistical threshold, bilateral postcentral gyri, orbitofrontal cortex (OFC), and lateral PFC. Activation in these areas remained correlated with SP severity after controlling for medication status, comorbidity and overall OC symptom severity, suggesting that these effects were specific to SP.
