Interhemispheric interactions between trunk muscle representations of the primary motor cortex
The mechanisms involved in the bilateral coordination of axial muscles of the trunk during unilateral arm movement are poorly understood. We thus investigated the nature of interhemispheric (between the two hemispheres of the brain) interactions in axial muscles during arm motor tasks in healthy subjects. By combining different methodologies, we showed that trunk muscles receive both inhibitory and facilitatory cortical outputs (from the brain) during activation of arm muscles. We propose that inhibition may be conveyed mainly through interhemispheric mechanisms and facilitation by subcortical mechanisms (below the cerebral cortex) or ipsilateral (same side of the body) pathways.