Effect of a visual-based sensory motor task on muscle tuning during a dynamic balance task

In this research, we explored visually-based sensory motor learning when a transformation was applied to the trajectory used to move and track a visual target in a virtual environment. The virtual task was controlled by the subject´s center of foot pressure (COP), where the COP position was mapped to an on-screen cursor. Target balloons appeared randomly on the screen; the subject was instructed to move the COP-controlled cursor to intersect and burst the balloons. A transformation was applied to the movement trajectory, which rotated the on-screen cursor counter-clockwise by 60°. The transformation required the subjects to update their spatial reference coordinates between the physical COP position and the on-screen cursor. To investigate learning during the transformation, electromyogram (EMG) data was recorded from the tibialis anterior and peroneus longus muscles. The muscle activity, calculated as the root mean square (RMS) of the EMG data, was calculated for each muscle as a function of the movement direction during movement initiation. The preferred direction (PD) for each muscle was then determined as the directional sum of the RMS values. The results showed a shift in the preferred direction (PD) of the muscles with learning.