Distinct within- and between-network functional dysconnectivity of the default-mode and frontoparietal networks in young individuals with first-episode bipolar disorder and major depressive disorder.

BACKGROUND

Evidence of whether disruptions in functional connectivity (FC), particularly within the default-mode network (DMN) and frontoparietal network (FPN), differ between first-episode bipolar disorder (BD) and major depressive disorder (MDD) is inconsistent.

METHODS

This study included 31 individuals (mean age, 25 years) with first-episode BD, 31 with MDD, and 31 healthy controls. Resting-state FC was assessed using magnetic resonance imaging. FC was analyzed in the DMN and FPN by using Dosenbach's 160 functional regions of interest.

RESULTS

FC within the DMN (ventromedial prefrontal cortex [vmPFC] and occipital region) and the FPN (ventral anterior PFC and intraparietal sulcus) as well as between the FPN and DMN, specifically between the ventral anterior PFC and occipital region and between the ventral PFC and precuneus, was higher in participants with BD than in healthy controls. Participants with MDD exhibited increased FC only within the anterior DMN, particularly between the vmPFC, superior frontal cortex, and ventrolateral PFC.

DISCUSSION: First-episode BD is characterized by more extensive FC alterations, with increased connectivity both within and across the FPN and DMN. By contrast, first-episode MDD presents with more localized FC disruptions, confined to the anterior DMN. These distinct patterns of functional dysconnectivity may underlie the greater cognitive impairments observed early in the course of BD compared with MDD.