Visual feedback distortion in a robotic environment for hand rehabilitation.

Robotic therapy offers a means of enhancing rehabilitation for individuals with chronic stroke or traumatic brain injury. The present research targets members of this population who demonstrate learned nonuse, a tendency to use affected limbs below the level of the individual's true capability. These individuals may not strive for difficult goals in therapy, which ultimately hampers their progress and the outcome of rehabilitation. Our research uses a paradigm called visual feedback distortion in which the visual feedback corresponding to force or distance is gradually changed by an imperceptible amount to encourage improved performance. Our first set of experiments was designed to assess the limits of imperceptible distortion for visual feedback concerning the force exerted or the distance moved by the index finger. A second set of experiments used these limits to gradually distort visual feedback in order to manipulate a subject's force or distance response. Based on this work, we designed a paradigm applying visual feedback distortion to the rehabilitation of individuals with chronic stroke and traumatic brain injury. Initial tests are reported for two subjects who participated in a six-week rehabilitation protocol. Each patient followed visual feedback distortion to levels of performance above that predicted by her performance during an initial assessment. Both patients showed functional improvements after participating in the study. Visual feedback distortion may provide a way to help a patient move beyond his or her self-assessed "best" performance, improving the outcome of robotic rehabilitation.