Temporal Facilitation Prior to Voluntary Muscle Relaxation

Abstract

We investigated the dominancy of excitability changes in motor cortex or spinal levels and temporal tuning mechanisms of muscle relaxation. We delivered transcranial magnetic stimulation and electric (H-reflex) stimulations relative to the application of the response signal under the reaction time task. The results showed that a significant change was found in only motor evoked potential during the prerelaxation phase, 30 ms after the response signal presented for muscle relaxation, but similar changes were not found in H-reflex. We suggested that this phenomenon, may be, reflects on excitation of corticospinal neurons, which consequently play an important role for muscle relaxation.

Keywords:

• H-reflex
• motor evoked potential (MEP)
• muscle relaxation
• reaction time task
• temporal tuning
• transcranial magnetic stimulation (TMS)