Effects of prefrontal repetitive transcranial magnetic stimulation on the autonomic regulation of cardiovascular function

Several protocols based on repetitive transcranial magnetic stimulation (rTMS) have been proposed for treatment of a variety of neurological disorders. Despite the widespread use, little is known about the effects of rTMS on the autonomic nervous control of the cardiovascular system. Twelve volunteers underwent rTMS sessions consisted in 8-min baseline recording, 8-min 0.7-Hz rTMS stimulation at 100 % of the motor cortex excitability threshold on the prefrontal cortex of one randomly assigned hemisphere. After 8-min recovery, the same procedure was performed on the contra-lateral hemisphere. Non-invasive (Portapres device) beat-by-beat blood pressure and heart period time series were recorded and analyzed by spectral and cross-spectral analysis in the low-frequency (LF ≈ 0.1 Hz) and in the high-frequency (HF = respiratory frequency) range. Repetitive TMS, particularly after stimulation of the right hemisphere, induced a slight increase in the parasympathetic drive and no effects on the sympathetic activity. There was a significant bradycardia after stimulation on the right hemisphere, not significant bradycardia after left stimulation. LF/HF ratio was 3.8 ± 2.1 during baseline and changed to 1.9 ± 0.6 during rTMS on the left and to 1.6 ± 0.6 during rTMS on the right. No significant changes were observed in blood pressure. Low-frequency rTMS of the prefrontal cortex induces a slight parasympathetic activation and no changes in the sympathetic function.