Language Network Connectivity of Euthymic Bipolar Patients Is Altered at Rest and during a Verbal Fluency Task

Area of Science:

• Neuroscience
• Psychiatry
• Cognitive Science

Background:

• Abnormalities in the language network (LN) are observed in psychiatric conditions like schizophrenia and bipolar disorder (BD).
• Altered LN asymmetry during resting state has been documented in BD patients.
• The stability of LN alterations during active language tasks remains under-investigated.

Purpose of the Study:

• To investigate the architecture and stability of the language network (LN) in euthymic bipolar disorder (BD) patients during both resting state and a verbal fluency task.
• To compare LN functional connectivity between BD patients and healthy controls (HC) under different task conditions.

Main Methods:

• Functional magnetic resonance imaging (fMRI) data were collected from 16 euthymic BD patients and 16 matched HC.
• Participants underwent an open-eyes resting state scan and a silent verbal fluency task.
• Spatial independent component analysis (ICA) was used to compute LN functional connectivity, followed by group comparisons.

Main Results:

• The LN in BD patients involved both left and right brain areas during rest and the verbal task.
• Compared to HC's left-lateralized LN, BD patients exhibited reduced lateralization with anterior clusters and disengagement of posterior language areas during the verbal fluency task.
• Altered LN connectivity in BD patients was consistent across resting and active linguistic states.

Conclusions:

• Reduced language lateralization may serve as a shared biological marker across the psychotic disorder spectrum.
• The impaired language network connectivity observed at rest in bipolar disorder is stable and persists during active language processing.
• These findings highlight the pervasive impact of bipolar disorder on neural systems supporting language.