Altered cerebellar gray matter and cerebellar-cortex resting-state functional connectivity in patients with bipolar disorder

•First study to investigate changes in cerebellar GMV and its functional connectivity exclusively in BP-I patients•Using the SUIT toolbox to isolate the cerebellum and identify the precise cerebellar regions involved in BP-I.•Found the decreased cerebellar gray matter and disrupted cerebellar-cortex resting-state functional connectivity in BP-I patients Bipolar disorder (BP) is a common psychiatric disorder characterized by extreme fluctuations in mood. Recent studies have indicated the involvement of cerebellum in the pathogenesis of BP. However, no study has focused on the precise role of cerebellum exclusively in patients with bipolar I disorder (BP-I). Forty-five patients with BP-I and 40 healthy controls were recruited. All subjects underwent clinical evaluation and Magnetic Resonance diffusion Tension Imaging scans. For structural images, we used a spatially unbiased infratentorial template toolbox to isolate the cerebellum and then preformed voxel-based morphometry (VBM) analyses to assess the difference in cerebellar gray matter volume (GMV) between the two groups. For the functional images, we chose the clusters that survived from VBM analysis as seeds and performed functional connectivity (FC) analysis. Between-group differences were assessed using the independent Students t test or the nonparametric Mann‐Whitney U Test. For multiple comparisons, the results were further corrected with Gaussian random field (GRF) approach (voxel-level P