Abstract
The present study investigated motor adaptation of point-to-point reaching movements to mirror feedback in the sagittal plane. This is a novel paradigm that both displaces and inverts the visual feedback of the right hand, showing it as the left hand. This environment creates a conflict between proprioceptive (and somatosensory) and visual feedback through the direction of errors produced as the result of a movement. Somatosensory, proprioceptive, and visual feedback are used to update internal models of the body and the space surrounding it in order to generate motor commands for upcoming movements. The process of updating internal models has been proposed as an explanation for motor adaptation. The first goal of the study was to characterize learning of the mirror perturbation. The results showed that adaptation occurred within a single training session, however the accuracy of the reaches made in the final perturbation reaches never returned to baseline. The second goal of the study was to determine the effect of mirror feedback on adaptation to a velocity-dependent force applied to the hand by a robotic manipulandum. The results show that subjects were able to adapt to the perturbation generated by the force while receiving mirror feedback at the same rate as when they were given correct visual feedback. These results suggest that visual and proprioceptive feedback can be processed in parallel, which allows the internal models to adjust to the deviating force relying solely on proprioceptive and somatosensory feedback.