Geoffrey J. McKendry’s MSc Thesis Proposal

Title: “The Influence of Sensorimotor Loop Delays in Maintaining Upright Stance”

Supervisor: Dr. Jean-Sébastien Blouin (Kinesiology)
Committee Members: Dr. Romeo Chua (Kinesiology), Dr. Mark Carpenter (Kinesiology)

Abstract: Standing upright is an apparently easy task for most humans yet its sensorimotor control is complex. Through neural circuits that include monosynaptic and polysynaptic spinal reflexes, as well as subcortical and trans-cortical sensorimotor loops, the human balance controller constantly adjusts muscle tone to maintain upright stance. Inherent to each of these balance loops are small delays due to the time it takes neurons to integrate and conduct signals. Thus the central nervous system must coordinate balance with sensory information reaching control centres at different times.

To investigate how the controller processes and responds to sensory information, researchers commonly use transient perturbations of the visual, vestibular, and/or somatosensory environment to measure evoked balance responses. Data from these methods can then be used to formulate computational models of how standing balance is controlled. Testing these models however requires manipulating balance dynamics under active rather than transient conditions. To do so a robotic device was developed to simulate the mechanics of a standing person while allowing subjects to experience novel balance conditions. One such condition is a simulation of increased sensorimotor loop delays in balance.

The aim of this proposed research project will be to compare balance stability between people with slow neural conduction in their central nervous system and healthy controls when artificial sensorimotor loop delays in balance are added. Furthermore, the proposed research will seek to determine whether differences in balance stability while artificial sensorimotor delays are present can be attributed to differences in stretch reflexes, subcortical responses, and/or trans-cortical responses.