Reduced Brain Electric Activity and Functional Connectivity in Bipolar Euthymia: An sLORETA Source Localization...

Area of Science:

• Neuroscience
• Psychiatry
• Biomedical Engineering

Background:

• Bipolar disorder (BD) is a chronic, relapsing-remitting illness.
• Euthymic states in BD are characterized by cognitive impairments, particularly in executive and language functions, despite the absence of manic or depressive symptoms.

Purpose of the Study:

• To investigate altered intracortical activity and functional connectivity in brain regions supporting cognitive functions in euthymic BD patients.
• To explore the relationship between neural activity/connectivity and cognitive deficits in BD.

Main Methods:

• Analysis of vigilance-controlled resting-state electroencephalography (EEG) in 13 euthymic BD patients and 13 healthy controls.
• Recomputation of EEG data into intracortical current density using low-resolution electromagnetic tomography across 8 frequency bands.
• Calculation of lagged coherences between 19 regions of interest (ROIs) to assess functional connectivity.

Main Results:

• Reduced temporal cortex activity observed in euthymic BD patients across all 8 EEG frequency bands.
• Significant reductions in large-scale functional connectivity in the delta, theta, alpha-2, beta-2, and gamma bands.
• Connectivity reductions involved prefrontal and temporal ROIs, suggesting widespread network alterations.

Conclusions:

• Euthymic BD patients exhibit decreased temporal cortex activation and impaired functional coordination between brain regions.
• These neural alterations may disrupt frontotemporal information flow, contributing to executive and language processing deficits in BD.
• Findings highlight the importance of assessing neural network function in euthymic BD for understanding cognitive impairments.