Simultaneously acquiring functional Near Infrared Spectroscopy (fNIRS) during Transcranial
Magnetic Stimulation (rTMS) offers the possibility of directly investigating superficial
cortical brain activation and connectivity. In addition, the effects of rTMS in distinct
brain regions without quantifiable behavioral changes can be objectively measured.
Healthy, nonmedicated participants age 18-50 years were recruited from the local community.
After written informed consent was obtained, the participants were screened to ensure
that they met inclusion criteria. They underwent two visits of simultaneous rTMS/fNIRS
separated by 2 to 3 days. In each visit, the motor cortex and subsequently the prefrontal
cortex (5 cm anterior to the motor cortex) were stimulated (1 Hz, max 120% MT, 10
s on with 80 s off, for 15 trains) while simultaneous fNIRS data were acquired from
the ipsilateral and contralateral brain regions.
Twelve healthy volunteers were enrolled with one excluded prior to stimulation. The
11 participants studied (9 male) had a mean age of 31.8 (s.d. 10.2, range 20-49) years.
There was no significant difference in fNIRS between Visit 1 and Visit 2. Stimulation
of both the motor and prefrontal cortices resulted in a significant decrease in oxygenated
hemoglobin (HbO(2)) concentration in both the ipsilateral and contralateral cortices.
The ipsilateral and contralateral changes showed high temporal consistency.
Simultaneous rTMS/fNIRS provides a reliable measure of regional cortical brain activation
and connectivity that could be very useful in studying brain disorders as well as
cortical changes induced by rTMS.