Influence on the excitability of spinal neural function of motor imagery in the thumb and index finger opposition position with orthosis

Abstract

In this study, we examined the effect on the excitability of the spinal neural function of motor imagery in the thumb and index finger opposition position with opponens orthosis. We analyzed 10 healthy subjects. In the motor imagery with orthosis trial, F-waves were recorded during relaxation (rest trial). Subsequently, the subjects practiced isometric thenar muscle activity at 30% maximum voluntary contraction using visual feedback for 1 min. Then, F-waves were recorded while the subjects performed motor imagery in the opposition position with orthosis (image with orthosis trial). After the motor imagery task, F-waves were recorded during relaxation (post-image trial). In the motor imagery without orthosis trial, F-waves were recorded during rest, image without orthosis, and post-image trials on another day. The relative values of persistence and F/M amplitude ratio during the image with orthosis trial were significantly higher than those of the without orthosis trial. Motor imagery with proprioceptive input can increase the excitability of spinal neural function. In clinical settings, it is important to perform motor imagery in a position similar to that during actual activity.