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Suprathreshold 0.2 Hz repetitive transcranial magnetic stimulation (rTMS) over the prefrontal area.

OBJECTIVE
This study was designed to evaluate the effects of suprathreshold 0.2 Hz repetitive transcranial magnetic stimulation (rTMS) to the prefrontal area and motor cortex on the cerebral cortex excitability.


METHODS
The study involved 15 healthy volunteers. With a concave circular coil, rTMS to Fz (bilateral dorsolateral prefrontal areas) was carried out for 100 sessions at a frequency of 0.2 Hz and an intensity 1.2 times the resting motor threshold. In addition, rTMS to M1 (primary motor cortex) (Lt motor hand area) was performed in a similar manner. Before and after rTMS, resting motor threshold, motor evoked potential, cortical silent period (CSP) and F wave were recorded, and their changes after rTMS as compared to the pre-rTMS were analyzed.


RESULTS
Neither Fz stimulation nor M1 stimulation caused any significant change in the resting motor threshold, motor evoked potential latency, amplitude or area as compared to the values measured before rTMS. No significant changes were seen in the amplitude and persistence of the F wave. However, while Fz stimulation produced significant prolongation of the CSP duration (p < 0.01), M1 stimulation produced no such prolongation. The sham stimulation (control) showed no significant prolongation of the CSP duration following either M1 or Fz stimulation.


CONCLUSION
These results suggest that suprathreshold 0.2 Hz rTMS of Fz induces a significant suppression of excitability in the primary motor cortex.