Selective Activation of Ipsilateral Motor Pathways in Intact Humans

摘要: It has been proposed that ipsilateral motor pathways play a role in the control of movements and recovery function after injury. However, extent to which are engaged voluntary activity intact humans remains largely unknown. Using transcranial magnetic stimulation over arm representation primary cortex, we examined motor-evoked potentials (iMEPs) proximal muscle during increasing levels unilateral bilateral isometric force sitting position. We demonstrate iMEP area amplitude decreased contraction homonymous (elbow flexor) muscles increased heteronymous flexor extensor) compared with contraction, regardless level tested. To further understand neuronal inputs involved effects, contribution from neck afferents projecting onto pathways. Medial (away tested) lateral (toward rotation head enhanced effects muscles, respectively. In contrast, flexion extension exerted nonspecific on iMEPs. Intracortical inhibition, cortex where iMEPs originated, showed modulation compatible changes conclude projections can be selectively modulated by contralateral likely involving circuits mediating asymmetric tonic reflexes acting, at least part, cortical level. The pattern actions may represent strategy engage behavior.