Distinct Pattern of Abnormal Brain Dynamics in Major Depressive Disorder Revealed

Resting-state functional magnetic resonance imaging (fMRI) scans showed a specific pattern of abnormal brain dynamics in the left putamen of patients with major depressive disorder compared with patients with bipolar disorder and healthy control subjects, according to a study published online in the Journal of Affective Disorders. 

“When bipolar disorder presents as the depressive state, it is often misdiagnosed as major depressive disorder,” researchers wrote. “However, few studies have focused on dynamic differences in local brain activity and connectivity between bipolar disorder and major depressive disorder.” 

To do so, researchers took resting-state fMRI scans to explore shared and specific patterns of abnormal dynamic brain segregation and integration in 106 patients with bipolar disorder, 114 patients with major depressive disorder, and 130 healthy control subjects. The analysis focused on dynamic amplitude of low-frequency fluctuations and dynamic functional connectivity. 

The study found disrupted dynamic balance between segregation and integration within the default mode network in both major depressive disorder and bipolar disorder. Specifically, compared with healthy control subjects, patients with major depressive disorder and bipolar disorder had decreased temporal variability of the dynamic amplitude of low-frequency fluctuations, or less dynamic segregation, in the bilateral posterior cingulate cortex/precuneus, researchers reported.

Meanwhile, patients with major depressive disorder, but not bipolar disorder, had significantly increased temporal variability of dynamic amplitude of low-frequency fluctuations, or more dynamic segregation, in the left putamen, compared with control subjects. 

Additionally, patients with major depressive disorder as well as those with bipolar disorder showed lower dynamic functional connectivity, or less dynamic integration, between the bilateral posterior cingulate cortex/precuneus and the left inferior parietal lobule compared with control subjects, according to the study. 

—Jolynn Tumolo 

Reference 

Luo Z, Chen G, Jia Y, et al. Shared and specific dynamics of brain segregation and integration in bipolar disorder and major depressive disorder: A resting-state functional magnetic resonance imaging study [published online ahead of print, 2020 Nov 13]. J Affect Disord. 2020;280(Pt A):279-286. doi:10.1016/j.jad.2020.11.012