Altered Brain Entropy as a predictor of antidepressant response in major depressive disorder

To explore the alterations and value of brain entropy (BEN) in major depressive disorder (MDD).85 MDD patients and 45 matched normal controls were recruited. MDD was diagnosed based on Diagnostic and Statistical Manual of Mental Disorders, 4th ed (DSM-IV). Symptoms of depression were assessed using the Hamilton depression scale-24 (HAMD-24) at baseline and follow-up (after 8-week treatment). All subjects underwent functional magnetic resonance imaging (fMRI) scans at baseline, and 30 MDD patients completed scans at 8th week. Whole brain BEN maps at each session was calculated using the BEN mapping toolbox.The 8-week antidepressant treatment improved symptoms for all MDD patients. As compared to normal controls, MDD showed reduced BEN in medial orbitofrontal cortex (MOFC)/subgenual cingulate cortex (sgACC), but increased BEN in motor cortex (MC). In MDD patients, higher baseline BEN in MOFC/sgACC and lower baseline BEN in temporal cortex (TC) were associated with higher baseline HAMD scores; higher baseline BEN in MOFC/sgACC and hippocampus were associated with greater reduction of HAMD scores after 8-week medication; greater reduction of HAMD scores after 8-week medication was correlated with greater BEN reduction in MOFC/sgACC but were correlated with less BEN reduction in MC, TC, fusiform gyrus (FG) and visual cortex (VC).The results highlighted MOFC/sgACC BEN as a potential marker for the prediction of MDD diagnosis and treatment effect. MDD might have increased MOFC/sgACC BEN but reduced BEN in visual and sensory-motor circuits corresponding to the imbalanced emotional and sensory-motor information processing. Reversing this unbalanced BEN would improve disease conditions in MDD.