Functional neuroimaging in obsessive-compulsive disorder

Abstract

Background and Aim: Obsessive-compulsive disorder (OCD) is a severe, highly prevalent and chronically disabling psychiatric disorder that usually emerges during childhood or adolescence. This paper aims to review the literature on functional neuroimaging in OCD, analysing the reported dysfunctional connectivity in the corticostriatothalamocor- tical circuitry. Method: This study included papers published in peer-reviewed journals dealing with functional imaging in OCD. Results: Striatal dysfunction, mainly of the caudate nu- cleus, leads to inefficient thalamic gating, resulting in hyper- activity within the orbitofrontal cortex (intrusive thoughts) and the anterior cingulate cortex (non-specific anxiety). Compulsions consist of ritualistic behaviours performed to recruit the inefficient striatum and neutralise unwanted thoughts and anxiety. Functional neuroimaging findings are discussed against the background of specific cognitive im- pairments, mainly regarding visuospatial processing, execu- tive functioning and motor speed. Cognitive deficits are par- tial and specific, matching imaging data. Conclusions: Sev- Received: September 28, 2010 Accepted after revision: January 23, 2011 Published online: June 21, 2011 Antonio Del Casale, MD NESMOS (Neurosciences, Mental Health, and Sensory Functions) Department School of Medicine and Psychology, Sant’Andrea Hospital, Sapienza University Via di Grottarossa 1035–1039, IT–00189 Rome (Italy) Tel. +39 063 377 5675, E-Mail antonio.delcasale @ uniroma1.it © 2011 S. Karger AG, Basel 0302–282X/11/0642–0061$38.00/0 Accessible online at: www.karger.com/nps Del Casale et al. Neuropsychobiology 2011;64:61–85 62 boys [9, 10] . Its clinical presentation in children and adults is generally similar [2] , but comorbidities differ [10] . Its usual onset is in late adolescence or early adult- hood, although it may occur from childhood to advanced age [11] . Onset is usually gradual. The course follows a chronic but fluctuating pattern, often related to stressful life events [12, 13] . Epidemiological surveys suggest that 50% or more people with OCD have at least one comor- bid psychiatric disorder, most commonly an anxiety dis- order or unipolar depression. Alcohol abuse/dependence is higher in OCD than in the general population [14] . Functional Neuroimaging Techniques Used to Study OCD Functional imaging studies are most useful to clarify the neural substrate underlying the pathophysiology of OCD. Positron emission tomography (PET), single pho- ton emission computed tomography (SPECT), proton magnetic resonance spectroscopy ( 1 H-MRS) and func- tional magnetic resonance imaging (fMRI) are the most frequently used techniques for this purpose. In the late 1980s, various groups [15–17] carried out PET studies and showed differences between OCD pa- tients and healthy volunteers ( table 1 ). SPECT has been first used in OCD by Machlin et al. [18] . They found al- terations in the medial frontal cortex (MFC). This tech- ni