An increased precision comparison of TMS-induced motor cortex BOLD fMRI response for image-guided versus function-guided coil placement.

Objective: To examine with high precision the differences between function-guided and image-guided transcranial magnetic stimulation (TMS).

Method: Using a calibrated TMS coil holder/positioner, interleaved TMS/functional magnetic resonance imaging (fMRI), and individualized anatomy-based regional normalization, we conducted a two-phase study of TMS coil positioning guided by either function (elicited thumb motion) or image-based targeting of the "hand knob," the anatomy associated with fMRI activation during thumb motion.

Results: In every case, image-guided TMS coil placement produced a thumb movement response at thresholds similar to those found under function guidance.