Functional connectivity alterations of the somatomotor network in euthymic bipolar disorder

While individuals with bipolar disorder are assumed to recover between mood episodes, some nevertheless experience lingering subsyndromal symptoms and suffer from cognitive and functional impairments. Here, we propose that these enduring impairments may be linked to aberrations in brain networks. To test this, we conducted a resting-state functional magnetic resonance imaging (fMRI) study and used network-based statistic to compare functional connectivity between euthymic individuals with bipolar disorder (N = 96) and healthy control individuals (N = 61) both within and between resting-state networks. We also investigated the association of functional connectivity with lingering psychomotor symptoms and illness severity in bipolar disorder. We found stronger functional connectivity between the somatomotor network and the frontoparietal network in individuals with bipolar disorder compared with healthy controls, but weaker functional connectivity within the somatomotor network as well as between the somatomotor and the visual network. Results remained after adjusting for antipsychotic medication. No significant association with psychomotor performance and illness severity was found. We conclude that stronger functional connectivity between the somatomotor and frontoparietal network might be associated with lingering symptoms in bipolar euthymia. Dysconnectivity within the somatomotor network might relate to psychomotor symptoms beyond the impact of medication. Our findings contribute to the sparse field of somatomotor network aberrancies in bipolar disorder and may present a potential target for brain stimulation treatment.