MRI-Based Multimodal Approach to the Assessment of Clinical Symptom Severity of Obsessive-Compulsive Disorder

Abstract

Objective This study assessed the associations of the abnormal brain activation and functional connectivity (FC) during memory processing and brain volume alteration in conjunction with psychiatric symptom severity in patients with obsessive-compulsive disorder (OCD).Methods Twenty-OCD patients and 20-healthy controls (HC) underwent T1-weighted and functional imaging underlying explicit memory task.Results In memory encoding, OCD patients showed higher activities in right/left (Rt./Lt.) inferior temporal gyrus (ITG), medial prefrontal cortex (MPFC), dorsolateral prefrontal cortex (DLPFC) and anterior cingulate cortex (ACC), compared with HC. In task-based FC, caudate (Cd) was positively connected with DLPFC and ITG in OCD, while HC showed different connectivities of Cd-ACC and Rt.-Lt. ITG. In memory retrieval, only Cd was activated in OCD patients. Cd was positively connected with DLPFC and vmPFC in OCD, but negatively connected between same brain areas in HC. OCD patients showed increased gray matter (GM) volumes of cerebellum, DLPFC, orbitofrontal cortex (OFC), hippocampus, Cd and ITG, and concurrently, increased white matter volumes of DLPFC. In OCD patients, GM volumes of Cd and OFC were positively correlated with HAMA and Y-BOCS. Functional activity changes of Cd in OCD were positively correlated with Y-BOCS.Conclusion Our findings support to accessing clinical symptom and its severity linked by brain structural deformation and functional abnormality in OCD patients.

A Review on P300 in Obsessive-Compulsive Disorder

“…Shorter N200 and P300 latencies in OCD compared to social phobia and normal controls were believed to be an OCD-associated phenomenon (speeding of cognitive processing) ( 48 ). In two studies, P300 amplitudes were significantly smaller in schizophrenia and OCD patients than in healthy subjects ( 54 , 60 ), a finding which is in line with the hypothesis of brain volume changes in both psychiatric illnesses ( 18 , 76 , 92 ).…”

“…One study described that patients with Tourette syndrome and OCD had shorter N200 and P300 latencies (43), thus confirming the above-mentioned common cortical hyperarousal state hypothesized for both conditions (93). Another article seems to be also in line with neuroimaging findings (18,94) when describing a P300 amplitude reduction in the anterior scalp regions in both OCD and Tourette syndrome with OCD patients (59).…”

“…The inferior frontal gyrus was found to be the most active brain area in the few OCD patients (71). Two additional studies (62,69) involving a higher number of subjects supported the concept that P300 is generated along a widely distributed network involving several brain areas implicated in OCD, as recently confirmed by some neuroimaging research (17,18), with both pharmacological treatment (62) and emotional drive (60) able to attenuate these functional changes.…”

“…On the other hand, the surgical disconnection of the orbito-frontal regions from limbic, thalamic, and striatal structures in severely affected patients improves symptoms of OCD (14). Moreover, neuroimaging studies in OCD demonstrate the involvement of the cortico-striato-thalamo-cortical loop, anterior cingulate cortex, prefrontal cortex, cerebellum, and hippocampus (15)(16)(17)(18).…”

“…P300 is generated along a widely distributed network, rather than by a specific region, including the hippocampus and the medial temporal lobe, the temporoparietal junction, and parietal areas, although the inferior and middle frontal, the orbito-frontal, and the cingulate cortices also contribute to it (26). For this reason, P300 involves several areas that seem to be implicated in the OCD pathophysiology (12)(13)(14)(15)(16)(17)(18).…”