Reproducible Brain Entropy (BEN) Alterations During Rumination

Rumination, characterized by recurrent and repetitive thinking, is closely associated with mental disorders such as depression. However, the neural mechanisms underlying this mental state remain poorly understood. In this study, we use a relatively novel neuroimaging analysis method-Brain Entropy (BEN) to quantitatively assess the irregularity, disorder, and complexity of brain activity, providing new insights into the neural mechanisms of rumination. We utilized a publicly available MRI dataset from three different scanners. The dataset included 41 healthy adult participants who completed identical fMRI tasks on IPCASGE, PKUGE, and PKUSIEMENS scanners. The time interval between the two visits was 22.0 {+/-} 14.6 days. The fMRI session included four runs: resting state, sad memory, rumination, and distraction. Whole brain voxel-wise BEN differences of task state and resting state, rumination and sad memory, distraction and sad memory, and rumination and distraction were tested and overlap regions after thresholded (p<0.05) across the three scanners were identified as exhibiting significant differences. The results demonstrate distinct alterations in BEN across mental states. Compared to the sad memory condition, decreased BEN was found in the visual cortex (VC) during rumination and decreased BEN in the posterior cingulate cortex/precuneus (PCC/PCu) during distraction. However, when compared to distraction, rumination showed increased BEN in the PCC/PCu. These findings suggest that rumination involves heightened internal focus and reduced processing of external environmental information. This study highlights BEN as a valuable metric for elucidating the neural mechanisms underlying rumination and its role in depression.