Evaluating rTMS Effects on Pre-SMA

Participants underwent real-rTMS [100% resting motor threshold (rMT)] and sham-rTMS (30% rMT) of pre-SMA in two separate sessions at least 1 week apart. The session order was counterbalanced across participants. For both sessions, over the course of 30 min 1800 biphasic pulses were applied over pre-SMA with a frequency of 1 Hz using a robot arm-controlled figure-eight coil (Ø, 2 × 75 mm; model MCF-B65, Medtronic). The coil was positioned in a lateral-to-medial orientation such that the strongest intracranial current went in a left-to-right direction, thus preferentially targeting the right hemisphere.
The individual resting motor threshold was determined in all sessions using the freeware TMS Motor Threshold Assessment Tool version 2.0 (MTAT 2.0; http://www.clinicalresearcher.org/software.htm), where the threshold is estimated using a maximum-likelihood strategy (“threshold hunting”). The rMT was assessed in the right hemisphere, and the motor evoked potential (MEP) of the left first dorsal interosseous was used as readout using the same coil type as the one used during the experiment. MEPs had to exceed 50 µV to be considered present. At the end of the stimulation, we asked participants to rate (on a scale of 1–10) “How effective do you feel the stimulation was?” (without explaining in further detail what was meant by “effective”) and “How uncomfortable did you find the stimulation?”