Multi-day training with vibrotactile feedback for virtual object manipulation.

Optimal function of prosthetic hands for activities of daily living requires knowledge of contact force; however, users of prosthetic hands must rely on visual feedback for object manipulation, requiring constant concentration. Vibrotactile stimulation was explored as a modality for force feedback over multiple testing sessions. Unimpaired participants (N=6) performed virtual object manipulation with their right index finger using both visual feedback and vibrotactile feedback corresponding to the applied force on the virtual object on four days over a 4-8 day period. Object manipulation outcome measures were user difficulty ratings, object displacement, and object average velocity. Participants were able to utilize the vibrotactile feedback to statistically significantly improve performance of all three outcome measures over the four days. Significant improvements in all outcome measures were seen between days 3 and 4, indicating that steady state performance may not have been reached. Results support the use of augmentative vibrotactile feedback for users of prosthetic hands, though future longer longitudinal study will be necessary to determine steady state performance.