Neuroimaging and neurocircuitry models in OCD

Recent structural, functional and metabolic neuroimaging studies have advanced the understanding of the brain mediation of OCD by orbitofrontal-subcortical circuitry, but much is still unknown or controversial. Phenotypic heterogeneity could account for many of the inconsistencies among previous neuroimaging studies of OCD. Current imaging studies are seeking to find the neurobiological basis of OCD symptom subtypes and predictors of treatment response. In future, combining genetics and basic neuroanatomic research with neuroimaging may clarify the pathophysiology of OCD. Although many lines of evidence point to dysfunction of orbitofrontal-subcortical circuitry in patients with OCD, questions remain unanswered. Some have suggested that orbitofrontal-subcortical hyperactivity in OCD may be the result of abnormal neuroanatomic development of these structures or a failure of pruning of neuronal connections between them. But so far no postmortem neuroanatomic studies of OCD exist to delineate its pathophysiology. The role of various neurochemical systems in OCD is similarly unclear. Based on an overview of imaging results, a neurocircuitry models will be presented which describes how frontal-subcortical brain circuitry may mediate OCD symptomatology, and which suggests a hypothesis for how treatments may ameliorate symptoms successfully.