Current direction-dependent modulation of human hand motor function by intermittent theta burst stimulation (iTBS)

Background: Transcranial magnetic stimulation (TMS) with different current directions can activate different sets of neurons. Current direction can also affect the results of repetitive TMS. Objective: : To test the influence of uni-directional intermittent theta burst stimulation (iTBS) using different current directions, namely posteroanterior (PA) and anteroposterior (AP), on motor behaviour. Methods: In a cross-over design, PA- and AP-iTBS was applied over the left primary motor cortex in 19 healthy, right-handed volunteers. Performance of a finger-tapping task was recorded before and 0,10,20, and 30 min after the iTBS. The task was conducted with the right and left hands separately at each time point. As a control, AP-iTBS with reduced intensity was applied to 14 participants in a separate session (AP(weak) condition). Results: The finger-tapping count with the left hand was decreased after PA-iTBS. Neither AP-nor AP(weak)- iTBS altered the performance. Conclusions: Current direction had a significant impact on the after-effects of iTBS. (C) 2017 Elsevier B.V. All rights reserved.