Effectiveness of a vibro-tactile feedback to cue a stepping response to a balance challenge.

Our purpose was to evaluate vibro-tactile feedback in cueing the ecologically important manoeuvre of making a `saving´ step response to movement of the support surface. Initial experiments to develop this technique were aimed at optimization of the type of transducer used to detect balance´s threat and of its sitting on the body to provide the most appropriate feedback of imbalance. A transient movement of a support platform was used to produce perturbations that would provoke a stepping response. Results on normal subjects and a range of patients with balance disorders are relatively contradictory. Whereas elderly subject with slower reaction times improved their reaction with the vibrotactile feedback patients with slowness showed no improvement. We speculate that the mode of action of such a prosthesis is not to improve sensory feedback detection but to facilitate high level decisional process. It is likely that in order to obtain the time lead necessary for sensory substitution one would have to develop a means of predicting when balance is likely to be jeopardized