Functional neural mechanisms of sensory phenomena in obsessive-compulsive disorder.

Sensory phenomena (SP) are aversive or uncomfortable sensations that accompany and/or drive repetitive behaviors in obsessive-compulsive disorder (OCD). Although SP are associated with significant distress and may respond less well to standard treatments than harm-related obsessions, little is known about their underlying neurobiology. The present study used functional magnetic resonance imaging (fMRI) to measure brain functioning related to severity of SP during a "body-focused" videos task designed to elicit activation in sensorimotor brain regions. Regression analysis examined the relationship between severity of SP and activation during task using permutation analysis, cluster-level corrected for multiple comparisons (family-wise error rate p < 0.05). The distribution of SP severity was not significantly different from normal, with both high- and low-severity scores represented in the OCD sample. Severity of SP was not correlated with other clinical symptoms in OCD including general anxiety, depression, or harm avoidance. When viewing body-focused videos, patients with greater severity of SP showed increased activity in the mid-posterior insula, a relationship that remained significant when controlling for other clinical symptoms, medication status, and comorbidities. At uncorrected thresholds, SP severity was also positively related to somatosensory, mid orbitofrontal, and lateral prefrontal cortical activity. These data suggest that SP in OCD are dissociable from other symptoms in the disorder and related to hyperactivation of the insula. Future work examining neural mechanisms of SP across different disorders (tics, trichotillomania) as well as with other imaging modalities will be needed to further understand the neurobiology of these impairing symptoms.