Interhemispheric resting state functional connectivity abnormalities in unipolar depression and bipolar depression

Area of Science:

• Neuroscience
• Psychiatry
• Medical Imaging

Background:

• Bipolar disorder (BD) depression is frequently misdiagnosed as unipolar depression (UD), leading to suboptimal treatment and outcomes.
• Understanding the neural underpinnings, specifically interhemispheric functional connectivity, is crucial for accurate diagnosis and treatment.

Purpose of the Study:

• To investigate and compare interhemispheric functional connectivity using voxel-mirrored homotopic connectivity (VMHC) in patients with BD depression, UD, and healthy controls.
• To identify similarities and differences in brain connectivity patterns between BD depression and UD.

Main Methods:

• Resting-state functional magnetic resonance imaging (fMRI) was employed in 36 patients with BD II depression, 32 patients with UD, and 40 healthy controls.
• Voxel-mirrored homotopic connectivity (VMHC) was calculated to measure functional connectivity between symmetric interhemispheric brain regions.

Main Results:

• Significant VMHC differences were observed in the posterior cingulate cortex (PCC), fusiform/lingual gyrus, and cerebellar lobes (CeAL, CePL) across the three groups.
• Both BD and UD groups exhibited decreased VMHC in several regions compared to controls, with no significant differences in VMHC between the BD and UD groups.
• No regions showed increased VMHC in either patient group compared to controls.

Conclusions:

• Depressive episodes in BD and UD share common deficits in interhemispheric coordination.
• These findings suggest a potential overlap in the neuropathological mechanisms underlying depression in both BD and UD.