Distinguishing functional and structural MRI abnormalities between bipolar and unipolar depression

Area of Science:

• Neuroscience
• Psychiatry
• Medical Imaging

Background:

• Bipolar disorder (BD) and unipolar major depressive disorder (MDD) share overlapping symptoms, complicating diagnosis.
• Understanding the neural underpinnings of spontaneous brain activity is crucial for differential diagnosis.

Purpose of the Study:

• To investigate differences in hippocampal and parahippocampal gyrus activity between BD and MDD patients.
• To identify potential neuroimaging biomarkers for distinguishing between BD and unipolar depression.

Main Methods:

• Resting-state functional magnetic resonance imaging (rs-fMRI) was used in 46 healthy controls (HC), 58 MDD patients, and 61 BD patients.
• Analysis included hippocampal and parahippocampal gyrus volumes, fractional amplitude of low-frequency fluctuation (fALFF), and regional homogeneity (ReHo).
• Correlation analyses examined relationships between brain measures and clinical variables (e.g., HAMD, HAMA, RBANS).

Main Results:

• The BD group showed significantly higher hippocampal fALFF compared to HC and MDD groups.
• BD patients exhibited increased ReHo in the hippocampus and parahippocampal gyrus versus HC.
• Hippocampal ReHo positively correlated with depression severity scores (HAMD, HAMA), but not cognitive function (RBANS).

Conclusions:

• Aberrant intrinsic brain activity in the hippocampus and parahippocampal gyrus, specifically altered fALFF and ReHo, can differentiate BD from unipolar depression.
• These findings suggest potential quantitative neuroimaging markers for clinical diagnosis.