Self-Induced Versus Reactive Triggering of Synchronous Hand and Heel Movement in Young and Old Subjects

Abstract

When asked to synchronize simulnaneously ipsilateral hand and heel movements, subjects behave differently whether they have to react to an external trigger signal or to synchronize movements in a self-pacing mode. In the reactive mode, the central commands seem to be centrally coactivated. In contrast, in the self-pacing mode, the schedule of the two motor commands appears inverted. The present study addresses the problem of how this remarkable capacity of the nervous system evolves with age. Results show that elderly are not impaired significantly in either modes of control for simultaneity. However, a breaking point in the capacity of performing a dual task has been observed in the three oldest subjects, suggesting an impairment similar to trouble associated with Parkinson’s disease.