Interhemispheric motor cortex influence during bimanual unloading.

Using the transcranial magnetic stimulation (TMS) of motor cortex we examined changes in the motor evoked potential (MEP) during natural bimanual unloading, during lifting of an equivalent weight by the contralateral arm while the ipsilateral forearm was held stationary (CONTRA) and during practice of unnatural unloading. During natural unloading, MEP amplitude decreased proportionally to the muscle activity. In CONTRA task MEP amplitude decreased, but the muscle activity was not changed.

Goal synchronization of bimanual skills depends on proprioception.

The present experiments in Human subjects were designed to test whether proprioceptive feedback plays a role in optimising bimanual synchronization in a goal-oriented familiar task. Goal-synchronization is a typical feature of bimanual everyday skills. The purpose of the study was to disturb proprioceptive signalling by means of vibrating the leading left limb while subjects performed a bimanual task on a drawer manipulandum.