The role of physiological complexity changes in resting-state EEG in clinical effectiveness of rTMS and tDCS in treatments of resistant depression

TL;DR

This paper reviews how changes in physiological complexity in EEG and ECG relate to the effectiveness of rTMS and tDCS in treating resistant depression, highlighting potential biomarkers for therapy outcomes.

Contribution

It compares complexity changes induced by rTMS and tDCS and explores their potential as biomarkers for predicting treatment success in depression.

Findings

Complexity changes correlate with treatment response.

EEG and ECG complexity may serve as future predictors.

Both modalities modulate neural dynamics through different mechanisms.

Abstract

The present literature about possible mechanisms behind the effectivity of noninvasive electromagnetic stimulation in major depressive disorder (MDD) is not very rich. Despite extensive research in applications for clinical practice, the exact effects are yet not clear. We are comparing our previous results about the complexity changes induced by repetitive Transcranial Magnetic Stimulation (rTMS), and transcranial direct current stimulation (tDCS) which are known to modulate neural dynamics. Also, we are reviewing different biomarkers of complexity changes connected to depression, and how they change with the stimulation. TDCS is low-intensity TES, known to have polarity specific effects (neuromodulatory effects), and rTMS is inducing an electric field in the tissue circumstantially via Faraday's law. Both nonlinear modalities of electromagnetic stimulation may affect the levels of physiological complexity in the brain. We also compare the changes of complexity in electroencephalogram (EEG) and electrocardiogram (ECG), as potential future predictors of therapy outcome.