A balance control model predicts how vestibular loss subjects benefit from a vibrotactile balance prosthesis

A balance control model was applied to interpret how subjects with a severe vestibular loss (VL) used vibrotactile information from a balance prosthesis to enhance balance control. Experimental data were from 5 VL subjects standing with eyes closed and responding to continuous pseudorandom surface tilts of the stance platform. Results showed that vibrotactile feedback information reduced sway at frequencies below ∼0.6 Hz, but vibrotactile feedback was less effective in reducing sway as stimulus amplitude increased. This experimental pattern was accurately predicted by the model, which was based on time-delayed sensory feedback control. The model predicted that changes to the vibrotactor activation scheme could improve performance of the prosthesis and demonstrated that further improvements might be possible if motor learning, acquired by practice and training, could increase VL subjects' reliance on the prosthesis.