Fronto-subcortical Functional Connectivity in Patients with Schizophrenia and Bipolar Disorders

Abstract

The question of a continuum or a dichotomy between schizophrenia and bipolar disorders is not clearly elucidated. The objective of the present study was to identify specific functional connectivity (FC) patterns in schizophrenia and bipolar disorders. Therefore, the aim was to explore FC within the language production network in response to a verbal fluency task in patients with schizophrenia, patients with bipolar disorders and healthy participants. We hypothesized that prefronto-subcortical FC patterns within the language production network differ between the three groups. Forty nine participants, comprising 15 patients with schizophrenia, 14 patients with bipolar disorders (DSM-IV) and 20 healthy controls were included in the study. FC was calculated using functional magnetic resonance imaging during a verbal fluency task between the activated pair-seed regions. Firstly, patients with schizophrenia presented a significantly reduced FC compared to controls within two pair-seed regions (medio-frontal cluster – left subcortical cluster and left fronto-lateral cluster – left subcortical cluster) while bipolar patients were not significantly different from healthy participants. Secondly, patients with schizophrenia compared to patients with bipolar disorders exhibited reduced FC within one pair-seed region (medio-frontal cluster – left subcortical cluster). Our results support the hypothesis of a specific medio-prefronto-striato-thalamic functional dysconnectivity implicated in the pathophysiology of schizophrenia. This fronto-subcortical dysconnectivity in schizophrenia could underlie language production symptoms observed in this pathology and could be a functional brain marker of schizophrenia.