Blood oxygenation changes resulting from subthreshold high frequency repetitive transcranial magnetic stimulation

Effects of high frequency repetitive transcranial magnetic stimulation (rTMS) with a subthreshold intensity on hemodynamic response in brain cortices (both motor and prefrontal cortices) was investigated using the functional near infrared spectroscopy (fNIRS) technique. FNIRS signals of the motor and prefrontal cortices were acquired in healthy volunteers (n=7) at rest and during rTMS intervention. A significant reduction in oxygenated hemoglobin (HbO) concentration during the entire stimulation process was observed from both motor and prefrontal cortices. Results showed that the fNIRS technique can provide a reliable measure of regional cortical brain activation that could be valuable in studying cortical excitability connectivity in combination with rTMS.