BOLD Imaging of Inhibition and Facilitation Induced by Paired-Pulse Transcranial Magnetic Stimulation: Feasibility and Reproducibility

Juergen Baudewig¹, Carsten Schmidt-Samoa¹, Peter Dechent¹

It is still a matter of controversy whether local hemodynamic changes detected with BOLD-fMRI are equally correlated to inhibitory and excitatory processes. Paired-pulse TMS is a well established method to induce inhibition or facilitation by varying the interstimulus intervals. We applied paired TMS pulses during simultaneous fMRI recordings at 3T in order to visualize the TMS-induced modulation of cortical excitability. EMG data acquired directly prior to the fMRI experiment proved the excitatory or inhibitory effect of long or short interstimulus intervals. Excitatory TMS pulse pairs resulted in increased BOLD responses in comparision to inhibitory stimulus intervals.