Echoplanar BOLD fMRI of brain activation induced by concurrent transcranial magnetic stimulation

RATIONALE AND OBJECTIVES. The authors demonstrate the feasibility of combining transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) inside an MR scanner to noninvasively stimulate and image regional brain activity. METHODS. Echoplanar blood oxygen level dependent (BOLD)-based fMRI studies of TMS response were performed on three human volunteers inside a standard 1.5 T MR scanner using independent computer control to interleave echoplanar image acquisition and stimulation of right thumb primary motor cortex with a nonferromagnetic TMS coil. RESULTS. Significant (P<0.001) response was observed in motor cortex under the TMS coil during stimulation compared to rest, as well in auditory cortex, the latter presumably due to the loud "snap" when the coil was pulsed. CONCLUSIONS. Concurrent TMS stimulation and echoplanar BOLD fMRI imaging is possible. This method has potential for tracing neural circuits with brain imaging, as well as investigating the effects of TMS.