[Effective connectivity characteristics of the thalamus and whole brain in obsessive-compulsive disorder patients...

Objective: To investigate altered effective connectivity patterns between thalamic subregions and the whole brain in obsessive-compulsive disorder (OCD) through Granger causality analysis (GCA). Methods: This retrospective study included 69 OCD patients hospitalized at the Second Affiliated Hospital of Xinxiang Medical University between January 2020 and June 2024 (OCD group) and 69 age, gender, and education-matched healthy volunteers (control group). Resting-state functional magnetic resonance imaging (rs-fMRI) data were acquired for all participants, and OCD symptom severity was assessed using the Yale-Brown obsessive-compulsive scale (Y-BOCS). Sixteen thalamic subregions were selected as seed regions based on the brainnetome atlas, and degree centrality (DC) analysis was used to assess the suitability of these subregions as seed regions. GCA was used to explore the effective connectivity between the seed points and the whole brain. Subsequently, the differences in DC and effective connectivity between the OCD group and the control group were compared, and the correlation between the effective connectivity values and Y-BOCS score were analyzed. Results: The OCD group consisted of 31 males and 38 females, aged (28.9±8.5) years; the control group comprised 32 males and 37 females, aged (30.3±8.2) years. There were no statistically significant differences in gender, age, or years of education between the two groups (all P>0.05). The OCD group exhibited lower DC in the bilateral thalamus compared to the control group (all P<0.001, false discovery rate correction). Compared to the control group, the OCD group showed stronger effective connectivity from the thalamus to the bilateral cuneus, left superior/inferior parietal lobule, and right precuneus [all P<0.05, Gaussian random field (GRF) corrected], whereas weaker effective connectivity was observed from the thalamus to the right superior occipital gyrus and inferior parietal lobule, as well as from the left inferior parietal lobule to the thalamus (all P<0.05, GRF corrected). Additionally, the OCD group demonstrated stronger effective connectivity from the left middle temporal visual area, cuneus/lingual gyrus, inferior parietal lobule, and postcentral gyrus to the thalamus, as well as from the right precuneus, parieto-occipital sulcus, and superior occipital gyrus to the thalamus (all P<0.05, GRF-corrected). In particular, the effective connectivity values for thalamic enhancement to area 40 of the caudal part of the left inferior parietal lobule (r=0.355, P=0.003) and to area 5 of the medial precuneus on the right (r=0.339, P=0.004) were positively correlated with the Y-BOCS total score. Conclusions: Abnormal effective connectivity of the thalamus to several brain regions within the parietal and occipital lobes in patients with OCD; enhanced effective connectivity of the thalamus to the left inferior parietal lobule and the right precuneus was associated with the severity of obsessive-compulsive symptoms.