Stance perturbation-evoked potentials in old people with poor gait and balance

Objective: Cerebral cortical potentials can be evoked by stance perturbatio n, and there is speculation that they represent the activation of supraspin al centers in preparation for the control and coordination of motor movemen ts that maintain balance. We sought to determine if these potentials differ ed in old people at risk of falls. Methods: Cortical potentials were generated by the sudden forward translati on of a weight-bearing platform in 8 healthy young subjects and in 33 old s ubjects stratified by their functional capacity. Dependent measures were co mpared with non-parametric tests of significance. Results: Perturbing the stance of young subjects produced a biphasic scalp potential centered at the vertex with an early positive peak at 60 ms and a larger, 45 mu V, negative peak at 123 ms. In old subjects the response was delayed and the vertex-negative component was smaller and bifid. The inter val between the two components of the negative peak was prolonged in a subg roup of old subjects with reduced mobility. Conclusions: Delays in sensory conduction may play a role in subsequent mal adaptive motor responses to stance perturbation that can result in falls an d injury in old people. (C) 1999 Elsevier Science Ireland Ltd. All rights r eserved.