Grant: Discovery Grants Program - Individual

Sensorimotor control relies on uncertain encoding of biologically-relevant events and motor actions. Uncertainty in both processes shapes the multisensory integration of self-motion cues that is critical for standing balance. The long-term objective of my research program is to reveal the neural principles underlying sensorimotor integration for standing balance. To address this overarching goal, the proposed research program will address how uncertainty influences central processing of sensory and motor cues relevant for standing balance and the adaptability of these mechanisms under three core short-term objectives: Objective 1. Understand the role of uncertainty in vestibular cues of self-motion. Objective 2. Determine how somatosensory and motor cues enable standing balance. Objective 3. Understand how the brain encoding of gravity affects standing balance. Scientific approach. The proposed research activities combine computational modelling and experimental approaches to formalize, predict and test the governing principles underlying the sensorimotor control of standing balance. In close collaboration with HQP under my supervision along with key collaborators, we will first determine if uncertainty in sensory encoding can be beneficial and whether uncertainty in the internal estimate of the body fluctuates. We propose a Bayesian inference approach using particles (particle filtering) to represent population of vestibular afferents encoding whole-body rotation. Based on predictions from this approach, we hypothesize that participants will exhibit history-dependent perceptual and ocular responses without an incorrect inference of rotation direction to well-controlled whole-body rotational stimuli. Second, we will use our NSERC-funded standing balance robot to characterize the natural statistics of somatosensory afferents encoding during standing balance, calculate their sensory thresholds and reveal how the balance controller combines uncertain sensory and motor information to give rise to a sense of preferred upright posture. We hypothesize that muscle spindle afferents will exhibit higher thresholds while balancing actively than when standing upright without balancing and that a probabilistic combination of uncertain sensory and motor information affords a sense of preferred posture. Finally, we will reveal how the brain adapts to altered gravity and the balance consequences of the brain's internal representation of gravity. We hypothesize that the brain will interpret a prolonged linear acceleration as a novel gravitational environment and that the brain's internal representation of gravity induces stereotypical balance responses. Impact. The proposed work will generate new knowledge on principles underlying sensorimotor integration related to human balance, will help train the next generation of integrative sensorimotor physiologists and will be translated through impactful peer-reviewed publications and conference presentations.