Investigating cortico-striatal pathophysiology in obsessive-compulsive disorders: Procedural learning and imaging probes

Obsessive-compulsive disorder (OCD) is a common condition afflicting up to 1% to 3% of the population worldwide (Rasmussen & Eisen, 1994). Its hallmark signs and symptoms include repetitive cognitive intrusions (Le., obsessions) and repetitive behaviors (Le., compulsions), as well as affective accompaniments (Le., anxiety; American Psychiatric Association, 1994). Although the current diagnostic scheme classifies OCD as an anxiety disorder, many investigators are inclined to focus on a so-called OC spectrum of disorders that share the commonality of repetitive symptoms (Hollander, 1993; McElroy, Phillips, & Keck, 1994). A medical model dictates that the classification of psychiatric disorders should reflect their respective underlying pathophysiologies. Unfortunately, contemporary psychiatric neuroscience data cannot yet fully support such an approach. OCDs are no exception in this regard, as the neural mechanisms underlying OCDs remain incompletely understood. Delineating pathophysiology represents a critical step toward improving diagnosis and treatment of psychiatric disease. Toward that end, there is great value in developing testable hypotheses regarding the pathophysiology of psychiatric diseases and proceeding to test them.