Autonomic Contributions in Compensatory Balance Control

This thesis examined Autonomic Nervous System activity evoked by postural instability. Autonomic reactions were assessed using measures of electrodermal activity at the surface of the skin. Perturbation-evoked electrodermal responses (EDRs) were consistently observed in conjunction with both upper and lower limb postural reactions. These autonomic responses were sensitive to perturbation amplitude, as well as experimental manipulations which did not influence the perturbation itself but which affected response execution. In particular, stimulus predictability and movement challenge modulated EDRs, although purely cognitive manipulations did not significantly affect autonomic responses. Probes examining the potential role of such autonomic potentials in compensatory balance control revealed that EDRs evoked during compensatory postural reactions were larger and more consistent than potentials evoked by purely motor or sensory stimuli, suggesting that evoked autonomic activity plays a role in compensatory behavior. While the specific role of autonomic contributions in compensatory balance control require further study, speculative models for autonomic contributions propose either feedback-based pathways for detection of instability to initiate the postural reaction, and/ or an adaptive role to higher centers important for establishing sensorimotor gain in future conditions. This thesis presents new evidence regarding basic neural mechanisms engaged in the recognition and response to postural instability, and future work may extend these findings in clinical populations with high fall incidence and offer clues as to alternative causes for falls and fall prevention.Ph