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

- Uni-directional iTBS was applied to the left primary motor cortex.
- Finger-tapping with the left hand was disturbed after posteroanterior iTBS.
- Current direction of iTBS had an impact on human motor behaviour.

BackgroundTranscranial 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.MethodsIn 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 (APweak condition).ResultsThe finger-tapping count with the left hand was decreased after PA-iTBS. Neither AP- nor APweak-iTBS altered the performance.ConclusionsCurrent direction had a significant impact on the after-effects of iTBS.