Startling acoustic stimuli can evoke fast hand extension movements in stroke survivors

Objective: A startling loud acoustic stimulus can involuntarily elicit planned movements, a phenomenon referred to as startReact. Following stroke, startReact elbow flexion in stroke survivors are improved from voluntary movements. Specifically, startReact elbow flexion in unimpaired individuals is not statistically different from stroke survivors in terms of onset latency and muscle activation patterns. As hand movements are particularly impacted by stroke, our objective was to determine if startReact was intact in the hand following stroke. Methods: Data were collected in 8 stroke survivors and 10 age-matched subjects performing hand extension following two non-startling acoustic stimuli representing "get ready" and "go" respectively. Randomly, the "go" was replaced with a startling acoustic stimulus. We hypothesized that (1) startReact would be intact during hand extension in stroke survivors and that (2) the latency of movement would be the same as in age-matched subjects. Results: We found that startReact was intact in stroke subjects and further that the onset latency of these movements was not different from age-matched subjects. Conclusions: We conclude that startReact is intact in the hand following stroke. Significance: An intact startReact response indicates that this reflex may be an attractive therapeutic target for initiating hand extension in stroke survivors.