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

Objective: Cerebral cortical potentials can be evoked by stance perturbation, and there is speculation that they represent the activation of supraspinal centers in preparation for the control and coordination of motor movements that maintain balance. We sought to determine if these potentials differed in old people at risk of falls. Methods: Cortical potentials were generated by the sudden forward translation of a weight-bearing platform in 8 healthy young subjects and in 33 old subjects stratified by their functional capacity. Dependent measures were compared 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 interval between the two components of the negative peak was prolonged in a subgroup of old subjects with reduced mobility. Conclusions: Delays in sensory conduction may play a role in subsequent maladaptive motor responses to stance perturbation that can result in falls and injury in old people. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.