Design of a Virtual Piano Trainer to Train Independent Finger Flexion for Persons Post-Stroke

Abraham Mathai MS, Gerard G. Fluet DPT, Alma S. Merians PT, PhD, Qinyin Qiu MS, Sergei Adamovich PhD.

Current neuroscience has identified rehabilitation approaches that seem to stimulate adaptive changes in the brains of persons following strokes. These approaches include, intense task-oriented training, bimanual activities and balancing proximal and distal upper extremity interventions to avoid competition for neural territory.

This paper describes the design and feasibility testing of a robotic / virtual environment system designed to train the hand and arm of persons who have had strokes. The system employs a simulated piano that presents tactile, auditory and visual feedback comparable to an actual piano. A system of strain gauge based data gloves and magnetic field position monitors record the position and orientation of both hands as well as the flexion of each finger at a rate of 100Hz. This data is translated into three dimensional movement of the virtual hand shown on the screen in a first person perspective.

This simulation provides accurate auditory feedback which is intrinsic to the activity of piano playing. Training programs include songs and scales that can be performed with one or both hands. The arm tracking features of this system allow patients to train their arm and hand as a single coordinated structure. An additional robotic interface can maintain inactive finger extension for participants unable to inhibit the mass grasp patterning common to stroke patients. The system includes an algorithm that adjusts task difficulty in proportion to subject performance.

The piano training simulation can be used with a supplementary haptic force feedback system for fingers and hand. It is a lightweight, force-reflecting exoskeleton that fits over the data glove. We developed an interface for the force feedback system and synchronized it with our virtual piano simulation. The force feed-back system inhibits the mass grasp pattern experienced by many subjects after a stroke by applying a constant force, around 4N, to the fingertips of non-active fingers, and no force is applied on the active finger, allowing the subject to move the active finger freely.

Two trials including three subjects with chronic CVA were conducted. Subjects completed 6 to 12 hours of training using the piano trainer without adverse events. All of the pilot subjects were able to perform training that combined hand and upper extremity work, isolated finger activity and bimanual activities, even if they had difficulty with these types of activity in real world environments. After training, all 3 subjects improved in their ability to press keys accurately and flex individual fingers independent from the other fingers of their hand. All three subjects also demonstrated performance improvement on the Wolf Motor Function Test, a clinical test of upper extremity function.