Repetitive transcranial magnetic stimulation frequency influences the hemodynamic responses in patients with disorders of consciousness

Repetitive transcranial magnetic stimulation (rTMS) emerges as a promising non-invasive neuromodulation technique for the treatment of patients with disorders of consciousness (DOC). The selection of rTMS parameters significantly influences the clinical therapeutic effects. However, the differences in spatiotemporal responsiveness of the brain under different rTMS stimulation frequencies remain unclear. In this pilot study, functional near-infrared spectroscopy (fNIRS) was used to evaluate the spatiotemporal differences in hemodynamic responses elicited by rTMS at different frequencies (1, 5, 10, 15, and 20 Hz) over left dorsolateral prefrontal cortex (F3). The results showed that the distribution patterns of the rTMS-evoked hemodynamic responses varied across different frequencies, indicating that rTMS frequency influences the hemodynamic responses in patients with DOC. Specifically, 10 Hz rTMS evoked strong positive hemodynamic responses over the frontal cortex, particularly in the right dorsolateral prefrontal cortex (R-DLPFC). Additionally, 20 Hz rTMS produced largepositive hemodynamic responses over the motor-related cortex, especially the right premotor cortex (R-PreM) and right primary sensorimotor cortex (PSMC). The current findings suggested that fNIRS can be used as a promising tool for evaluating the effects of rTMS in patients with DOC. Moreover, it provides useful guidance for the personalized design of rTMS parameters in a clinical environment.