This work was supported by NSF DBI 2015317 as part of the NSF/CIHR/DFG/FRQ/UKRIMRC Next Generation Networks for Neuroscience Program and the NSF US-German Collaborative Grant 1608111; and NSF 1943483.
Artificial neural networks, Locomotion -- Computer simulation
This work presents an in-depth numerical investigation into a hypothesized two-layer central pattern generator (CPG) that controls mammalian walking and how different parameter choices might affect the stepping of a simulated neuromechanical model. Particular attention is paid to the functional role of features that have not received a great deal of attention in previous work: the weak cross-excitatory connectivity within the rhythm generator and the synapse strength between the two layers. Sensitivity evaluations of deafferented CPG models and the combined neuromechanical model are performed. Locomotion frequency is increased in two different ways for both models to investigate whether the model’s stability can be predicted by trends in the CPG’s phase response curves (PRCs). Our results show that the weak cross-excitatory connection can make the CPG more sensitive to perturbations and that increasing the synaptic strength between the two layers results in a trade-off between forced phase locking and the amount of phase delay that can exist between the two layers. Additionally, although the models exhibit these differences in behavior when disconnected from the biomechanical model, these differences seem to disappear with the full neuromechanical model and result in similar behavior despite a variety of parameter combinations. This indicates that the neural variables do not have to be fixed precisely for stable walking; the biomechanical entrainment and sensory feedback may cancel out the strengths of excitatory connectivity in the neural circuit and play a critical role in shaping locomotor behavior. Our results support the importance of including biomechanical models in the development of computational neuroscience models that control mammalian locomotion.
© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
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Deng, K.; Hunt, A.J.; Szczecinski, N.S.; Tresch, M.C.; Chiel, H.J.; Heckman, C.J.; Quinn, R.D. Biomechanical and Sensory Feedback Regularize the Behavior of Different Locomotor Central Pattern Generators. Biomimetics 2022, 7, 226. https://doi.org/10.3390/biomimetics7040226