Is there a cerebellar compensatory effort in first-episode, treatment-naive major depressive disorder at rest?

This study was undertaken to explore whether there is a cerebellar compensatory response in patients with first-episode, treatment-naive major depressive disorder (MDD). The cerebellar compensatory response is defined as a cerebellar hyperactivity which would be inversely correlated with both the activation of the functionally connected cerebral regions and the depression severity.

Resting-state functional magnetic resonance imaging (fMRI) data of 24 patients with MDD and 24 healthy subjects were analyzed with the fractional amplitude of low-frequency fluctuations (fALFF) and functional connectivity (FC) methods. The structural images were processed with the voxel-based morphometry (VBM) method.

Compared to healthy controls, depressed patients had significantly increased fALFF in the left Crus I and the left cerebellar lobule VI. FC analysis of these two seeded regions found that depressed patients had increased FC between the left Crus I and the right hippocampus, but had decreased FC between the left Crus I and the left inferior parietal lobule (IPL), and between the left cerebellar lobule VI and bilateral inferior temporal gyrus. No correlation was observed between the abnormal fALFF of the seeds and their connected regions and the depression severity or the executive function. The VBM results did not show significant reduction in gray or white matter volume in any above-mentioned region.

Our findings suggest that increased cerebellar activity at resting state may be a disease state phenomenon but not a compensatory response to the dysfunction of the default mode network (DMN) in MDD.