Effects of repetitive transcranial magnetic stimulation on prefrontal-temporal network dynamics

Abstract

Repetitive transcranial magnetic stimulation (rTMS) is a form of non-invasive brain stimulation that is widely used to modulate neural activity. It delivers time-varying magnetic fields that induce electric currents in the targeted brain regions, influencing neural excitability and connectivity. Specifically, rTMS is commonly used to target the left dorsolateral prefrontal cortex (dlPFC) due to its relevance in clinical applications such as major depression disorder (MDD) treatment. Although rTMS is clinically utilized for patients, therapeutic outcomes in patients tend to be highly variable, and the underlying neural mechanisms remain incompletely understood. To address this problem, we employed invasive local field potential (LFP) recordings with non-human primates (NHPs) to provide the high quality recordings and make a better understanding of mechanism at the circuit level. In this study, we investigated the neural effect induced by rTMS with the stimulation targeted left dlPFC with a main focus on power changes and coherence dynamics. We found that 10 Hz rTMS applied to the left dlPFC can modulate functional connectivity in both local region (prefrontal) and distal region (temporal) in non-human primates. This indicates the propagation effect of rTMS. We also found that low-frequency coherence shows an initial increase followed by a decrease, while medium-frequency coherence initially decreases and then rebounds. This suggests that this modulatory effect shows a frequency-specific manner. Overall, we used invasive LFP recordings in non-human primates to show that 10 Hz rTMS of the left dlPFC induces frequency-specific changes in functional connectivity between prefrontal and temporal regions, indicating a propagation of rTMS effects that could be translated to future human research.