Abnormal functional network of the thalamic subregions in adult patients with obsessive-compulsive disorder

•Increased fractional amplitude of low-frequency fluctuation (fALFF) values were found in the bilateral thalamus in obsessive-compulsive disorder (OCD).•In the obsessive-compulsive group, abnormal functional connectivity was found in the following thalamic subregions: right posterior parietal thalamus (PPtha), right occipital thalamus (Otha) and left sensory thalamus (Stha).•Increased functional connectivity between right PPtha and left middle occipital gyrus correlated with symptom severity in OCD group.•These regions including occipital, prefrontal and parietal cortex were involved in the pathophysiology of OCD. The thalamus plays an important role in pathological mechanisms underlying obsessive-compulsive disorder (OCD). As the thalamus is a heterogeneous brain region, functional connectivity (FC) between thalamic subregions and other brain regions is worth investigating in OCD. In addition, the relationship between abnormal FC and clinical symptoms is still unclear. In this study, we used resting-state functional magnetic resonance imaging to scan 45 OCD patients and 43 well-matched healthy controls (HCs). Thalamic subregions were defined according to the Human Brainnetome Atlas. The fractional amplitude of low-frequency fluctuations (fALFF) and FC seeding-based connectivity were compared using a two-sample t-test. Correlations between abnormal FC and clinical symptoms were analyzed in OCD patients. Compared with HCs, increased fALFF was found in the bilateral thalamus, and increased FC was observed between the right posterior parietal thalamus (PPtha) and left middle occipital gyrus (LMOG) and between the right occipital thalamus (Otha) and right middle occipital gyrus (RMOG) in OCD patients. In addition, OCD patients had reduced FC between the left sensory thalamus (Stha) and left orbital inferior frontal gyrus, right PPtha and left prefrontal cortex, and between the right Otha and left inferior parietal gyrus (LIPG), respectively. Within the OCD group, the FC between right PPtha-LMOG was correlated with severity of clinical symptoms. These results revealed that the FC between the thalamus and occipital lobe is related to obsessive-compulsive symptoms in OCD patients. This finding provides more accurate information about the involvement of the thalamus in the pathophysiology of OCD.