Title: Internal representation of time and body dynamics during standing balance
Supervisor: Dr. Jean-Sébastien Blouin
Committee members: Dr. Calvin Kuo, Dr. Patrick Forbes
Abstract: The integration of multisensory inputs plays a crucial role in building an internal representation of our body and the external world. Self-generated motor commands affect our movements based on the dynamics of the body, resulting in body motion that is encoded by sensory information and reaches central neural structures after certain delays. Standing balance is a critical task requiring multisensory integration that involves large sensorimotor delays due to the distance between cortical/subcortical structures and the lower limbs. These delays and their interaction with body dynamics partially dictate the margins of stability for the control of balance. Although whole-body dynamics have been modeled and simulated in robotic systems using an inverted pendulum model for human standing balance, the internal representation and interaction between body dynamics and sensorimotor delays remains to be defined. Using a novel robotic balance system with the ability to move in both the anteroposterior (AP) and mediolateral (ML) directions, I will study how changing whole-body dynamics and sensorimotor delays affect standing balance using whole-body sway and perception metrics. Based on computational model simulations and previous studies, I hypothesize: 1) Increases in body dynamics will increase balance stability 2) Whole-body dynamics and sensorimotor delays will share internal representations as identified by subjective perceptual equality 3) Whole-body dynamics and sensorimotor delays will combine linearly for the control of standing balance to compensate for increases in postural oscillations previously reported with imposed sensorimotor delays. I propose to test 30 healthy participants while they balance on our robotic balance system in response to manipulations in whole-body dynamics and/or imposed sensorimotor delays. The proposed research will contribute to the understanding of how the nervous system internally represents time and body dynamics and how these variables affect the control and perception of balance.