Transient motor evoked potential suppression following a complex sensorimotor task

Abstract

<h4>Objective</h4>To investigate the mechanism involved in the transient suppression of the response to transcranial magnetic stimulation (TMS) following repeated performance of a complex sensorimotor training task (ST).<h4>Methods</h4>A total of 19 healthy subjects participated in 4 experiments, all involving performance of the grooved pegboard test (GPT). The experiments investigated the effect of the ST on corticospinal and intracortical excitability, spinal excitability and maximal pinch grip force.<h4>Results</h4>Motor evoked potential amplitude decreased significantly following the ST in both muscles tested and this was associated, but not correlated, with a decrease in the time taken to perform the GPT. There was no change in intracortical inhibition or facilitation (tested at interstimulus intervals of 3 and 10 ms, respectively). M wave amplitude was unchanged, as were F wave amplitude, latency and persistence and there was no evidence of muscle fatigue.<h4>Conclusions</h4>The reduction in corticospinal excitability was short lasting (<10 min) and was not accompanied by changes at the spinal or peripheral level, suggesting that other intracortical circuits may be involved.<h4>Significance</h4>Repeated performance of motor tasks can result in both short- and long-term modulation of motor cortical excitability. However, the relationship between changes in corticospinal excitability and motor performance is complex and critically dependent upon task type and duration.