Visuo-tactile stimulated virtual mirror therapy (ViTaS-VMT) system for enhancing motor-related brain activities: Application on two amputees

To enhance the degenerated brain signal of amputees on motor area, a visuo-tactile stimulated virtual mirror therapy system was developed. The system consists of a motion-tracking glove, a vibration motor, and a monitor-integrated table. The system can provide virtual hand illusion for body agency and combine visuo-tactile stimulation to induce body ownership on the virtual hand. The virtual hand then mimics the healthy hand like mirror therapy, and subjects perform grasping with both hands while observing the mirrored virtual hand on the amputated side. The training lasted three days, including the gradual exposure to the system to measure the difference in brain activity on the first day. We measured electroencephalogram (EEG) during training, and functional magnetic resonance imaging (fMRI) of grasping was measured before and after the training. Two amputees volunteered for this preliminary study. Both participants showed changes in motor-related brain activity, with consistent increases in event-related desynchronization (ERD) amplitude, particularly in the supplementary motor area (SMA) and primary motor cortex. These findings suggest the system's potential to enhance motor-related neural processes. We believe that the results of this preliminary study have provided evidence that the proposed system can reproduce the learning process and that brain activation can be improved by using the system. Based on the results, a future study will expand the number of subjects and the duration of training to provide a quantitative clinical evaluation of the proposed system.