Podium 1: Skeletal Disorders, Treatments & Rehabilitation
Subthreshold Tms For Cortical Inhibition Of Long-Latency Responses In One Forearm Muscle
Cody A Helm, Kyle Grossman, Sheldon-Anthony Amofah, Fabrizio Sergi
University of Delaware
In-depth knowledge of the function of the reticulospinal tract (RST) would improve our understanding of its role in stroke recovery. Function of the RST can be evaluated using long-latency responses (LLR). Transcranial magnetic stimulation (TMS) can modulate corticospinal output to independently quantify function of the RST. Thus, methods that combine TMS and stretch reflexes can study RST function associated with LLRs. We combined single subthreshold TMS pulses, wrist perturbations to evoke forearm LLR, and surface electromyography to determine the effect of subthreshold TMS stimulus intensity and timing on the long-latency response amplitude (LLRa). We divided 24 participants into two groups (N=12) to test two TMS intensities (90% or 95% Active Motor Threshold). TMS pulses were timed to arrive at the muscle at three different timings (0ms, 20ms, 50ms) prior to perturbation onset. Perturbation only and background only conditions were included as controls. TMS timing had a significant effect on LLRa (p<0.0001*) with no significant effect between TMS intensities (p=0.6719). Furthermore, TMS pulse timing of 50 ms resulted in the greatest reduction in LLRa (p=0.0001*). In conclusion, subthreshold TMS can significantly reduce the LLRa and the RST may contribute to motor commands when corticospinal output is reduced.
Research Area: Neuromuscular Modeling & Control