Cerebral Cortex 2015 Jul;25(7):1981-6.
Disruption of Locomotor Adaptation with Repetitive Transcranial Magnetic Stimulation Over the Motor Cortex
Julia T. Choi1,3, Laurent J. Bouyer2 and Jens Bo Nielsen3
1University of Copenhagen, Denmark, 2Université Laval and Center for Interdisciplinary Research in Rehabilitation and Social Integration, Québec City, Canada, and 3 University of Massachusetts Amherst, Amherst, MA, USA
Locomotor patterns are adapted on a trial-and-error basis to account for predictable dynamics. Once a walking pattern is adapted, the new calibration is stored and must be actively de-adapted. Here, we tested the hypothesis that storage of newly acquired ankle adaptation in walking is dependent on corticospinal mechanisms. Subjects were exposed to an elastic force that resisted ankle dorsiflexion during treadmill walking. Ankle movement was adapted in <30 strides, leading to after-effects on removal of the force. We used a crossover design to study the effects of repetitive transcranial magnetic stimulation (TMS) over the primary motor cortex (M1), compared with normal adaptation without TMS. In addition, we tested the effects of TMS over the primary sensory cortex (S1) and premotor cortex (PMC) during adaptation. We found that M1 TMS, but not S1 TMS and PMC TMS, reduced the size of ankle dorsiflexion after-effects. The results suggest that suprathreshold M1 TMS disrupted the initial processes underlying locomotor adaptation. These results are consistent with the hypothesis that corticospinal mechanisms underlie storage of ankle adaptation in walking.
