When motor control hangs in the balance: Sensorimotor learning during balance-challenging conditions

Maintaining balance while moving is fundamental for safe and successful motor performance. However, this aspect of daily movement is often overlooked in experimental paradigms that assess adaptation during constrained and/or isolated tasks. Consequently, we cannot easily extrapolate the results from these studies to naturalistic motor behaviours. The goal of this thesis is to determine how the necessity to maintain balance during unconstrained movement affects sensorimotor learning. For my first study, I assessed how challenging balance during adaptation affects generalization of learning. Four groups of participants adapted to a new visuomotor mapping induced by prism lenses while performing either a standing-based reaching or walking task, with or without a manipulation that challenged balance. To assess generalization, participants performed a single trial of each of the other group's tasks without the prisms. I found that both the reaching and walking balance-challenged groups showed greater generalization to their equivalent, non-adapted task compared to the balance-unchallenged groups. I also found that challenging balance modulated generalization across the reaching and walking tasks. For my second study, I tested how challenging balance affected motor memory retention. To do this, the same four groups of participants returned to the lab and repeated their adaptation protocol one week later. I found that only the walking groups demonstrated faster relearning (or savings) during re-exposure to the prisms. Crucially, I found that challenging balance significantly enhanced savings during walking. In my third study, I determined how a stability consequence associated with movement errors affected sensorimotor learning. Two groups of participants adapted to a new visuomotor mapping while performing a precision walking task either with or without the possibility of experiencing a slip perturbation when making errors. I assessed generalization of learning across two visually guided walking tasks and motor memory consolidation. To assess consolidation, I introduced an opposite direction visuomotor mapping following adaptation and evaluated relearning one week later. I found that the experiencing a physical consequence when making errors enhanced generalization and motor memory consolidation. Overall, this thesis provides a novel perspective on how the necessity for balance control contributes to sensorimotor learning, which has intriguing implications for the development of rehabilitation interventions.