Neurocircuit models of obsessive-compulsive disorder: limitations and future directions for research

Abstract

Obsessive-compulsive disorder (OCD) is a common psychiatric condition classically characterized by obsessions (recurrent, intrusive and unwanted thoughts) and compulsions (excessive, repetitive and ritualistic behaviors or mental acts). OCD is heterogeneous in its clinical presentation and not all patients respond to first-line treatments. Several neurocircuit models of OCD have been proposed with the aim of providing a better understanding of the neural and cognitive mechanisms involved in the disorder. These models use advances in neuroscience and findings from neuropsychological and neuroimaging studies to suggest links between clinical profiles that reflect the symptoms and experiences of patients and dysfunctions in specific neurocircuits. Several models propose that treatments for OCD could be improved if directed to specific neurocircuit dysfunctions, thereby restoring efficient neurocognitive function and ameliorating the symptomatology of each associated clinical profile. Yet, there are several important limitations to neurocircuit models of OCD. The purpose of the current review is to highlight some of these limitations, including issues related to the complexity of brain and cognitive function, the clinical presentation and course of OCD, etiological factors, and treatment methods proposed by the models. We also provide suggestions for future research to advance neurocircuit models of OCD and facilitate translation to clinical application.

Figure 1. Overview of the neurocircuit-based taxonomy to guide treatment for OCD proposed by Shephard et al. The figure shows the five neurocircuits implicated in OCD and their associated clinical profiles and suggested treatment approaches outlined by Shephard et al. ALIC = anterior limb of the internal capsule; CBT = cognitive behavioral therapy; dCaud = dorsal caudate nucleus; dlPFC/dmPFC = dorsolateral/dorsomedial prefrontal cortex; fMRI = functional magnetic resonance imaging; IFG = inferior frontal gyrus; NAcc = nucleus accumbens; OCD = obsessive-compulsive disorder; OFC = orbitofrontal cortex; Pput = posterior putamen; rTMS = repetitive transcranial magnetic stimulation; SMA = supplementary motor area; SSRIs = selective serotonin reuptake inhibitors; STN/VS = subthalamic nucleus/ventral striatum; tDCS = transcranial direct current stimulation; vCaud = ventral caudate nucleus; vlPFC = ventrolateral prefrontal cortex; vmPFC = ventromedial prefrontal cortex.