Electroconvulsive therapy modulates critical brain dynamics in major depressive disorder patients

Electroconvulsive therapy (ECT) is widely considered as an effective and fast-acting option for treating patients with major depressive disorder (MDD). However, the neural basis underlying this powerful therapy remains uncertain. Recent studies have suggested that the healthy brain may operate near a critical state, which may reflect a balance between neuronal excitation and inhibition.

In the present study, we investigated whether there are any changes regarding criticality in MDD and, if so, whether ECT can reverse them. Critical dynamics analyses were performed on resting-state functional magnetic resonance imaging (rs-fMRI) data collected from 39 MDD patients and 38 healthy controls (HCs).

We found that compared with HCs, MDD patients, especially those who responded positively to ECT, tended to have smaller average avalanch sizes and lower branching ratios, suggesting a sub-critical state, at both the whole-brain and functional network levels. Importantly, ECT effectively corrected such anomalies, accompanied by enhanced degree centrality and functional connectivity of high-degree nodes located in the networks including the default-mode and the frontoparietal networks.

These results indicate that ECT can modulate large-scale brain dynamics of MDD patients to be closer to criticality. Our study sheds new light on the pathology of MDD and the network mechanism by which ECT influences treatment.