Adaptive Multi-Objective Control Explains How Humans Make Lateral Maneuvers While Walking

• Published in: bioRxiv
• Main Authors: Desmet, David M, Cusumano, Joseph P, Dingwell, Jonathan B
• Format: Paper
• Language: English
• Published: Cold Spring Harbor Cold Spring Harbor Laboratory Press 29.10.2022
• Subjects: Computer applications; Feet; Mathematical models; Walking
• DOI: 10.1101/2022.03.21.485079

To successfully traverse their environment, humans often perform maneuvers to achieve desired task goals while simultaneously maintaining balance. Humans accomplish these tasks primarily by modulating their foot placements. As humans are more unstable laterally, we must better understand how humans modulate lateral foot placement. We previously developed a theoretical framework and corresponding computational models to describe how humans regulate lateral stepping during straight-ahead continuous walking. We identified goal functions for step width and lateral body position that define the walking task and determine the set of all possible task solutions as Goal Equivalent Manifolds (GEMs). Here, we used this framework to determine if humans can regulate lateral stepping during non-steady-state lateral maneuvers by minimizing errors consistent with these goal functions. Twenty young healthy adults each performed four lateral lane-change maneuvers in a virtual reality environment. Extending our general lateral stepping regulation framework, we first re-examined the requirements of such transient walking tasks. Doing so yielded new theoretical predictions regarding how steps during any such maneuver should be regulated to minimize error costs, consistent with the goals required at each step and with how these costs are adapted at each step during the maneuver. Humans performed the experimental lateral maneuvers in a manner consistent with our theoretical predictions. Furthermore, their stepping behavior was well modeled by allowing the parameters of our previous lateral stepping models to adapt from step to step. To our knowledge, our results are the first to demonstrate humans might use evolving cost landscapes in real time to perform such an adaptive motor task and, furthermore, that such adaptation can occur quickly - over only one step. Thus, the predictive capabilities of our general stepping regulation framework extend to a much greater range of walking tasks beyond just normal, straight-ahead walking. Competing Interest Statement The authors have declared no competing interest. Footnotes * Minor revisions to a couple of figures... Added a brief Supplement to address a question from a journal reviewer. NOTES: I've provided a DOI for the data. Data are being archived at Dryad. They are processing everything, so this might not be "live" quite yet, but will be the final DOI link once they've approved our submission (soon). Lastly, this paper has been accepted for publication at PLoS Computational Biology and their version should also appear soon. Please let me know if I need to do anything further to link this pre-print to the final version once published. Thank you! Jon Dingwell * https://doi.org/10.5061/dryad.tx95x6b1x