The Common and Distinct Altered Functional Activation Of White Matter In Major and Bipolar Depressive Disorders

Distinguishing major depressive disorder (MDD) and bipolar depressive disorder (BDD) is a clinical challenge. White matter tracts structural abnormalities have been documented in MDD and BDD. However, the function changes of white matter (WM) are still unclear across MDD and bipolar disorder. A total of 244 participants (MDD = 98, BDD = 54 and healthy controls [HC] = 92) were included in the present study. Amplitude of low-frequency fluctuations (ALFF) was adopted to measure the functional activation of WM. Compared with HC, MDD exhibited specific ALFF abnormalities in brainstem, right corona radiata (CR), but BDD showed specific ALFF abnormality in the left thalamus-WM. The decreased ALFF in left CR was revealed both in MDD and BDD compared with HC. The opposite correlation between the left CR and depressive severity in MDD was observed. Our findings provided a preliminary exploration from the perspective of WM functional signals, which suggest that abnormally reduced functional activation in WM provide evidence and new view to understand the pathophysiology of MDD and BDD.