Evaluating functional roles of phase resetting in generation of adaptive human bipedal walking with a physiologically based model of the spinal pattern generator |
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Authors: | Shinya Aoi Naomichi Ogihara Tetsuro Funato Yasuhiro Sugimoto Kazuo Tsuchiya |
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Institution: | (1) Center for BioDynamics, Boston University, 111 Cummington Street, Boston, MA 02215, USA;(2) Department of Neurobiology and Behavior, Cornell University, Seeley Mudd Hall, Ithaca, NY 14853, USA;(3) Mathematics Department, Cornell University, 565 Malott Hall, Ithaca, NY 14853, USA |
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Abstract: | The central pattern generators (CPGs) in the spinal cord strongly contribute to locomotor behavior. To achieve adaptive locomotion,
locomotor rhythm generated by the CPGs is suggested to be functionally modulated by phase resetting based on sensory afferent
or perturbations. Although phase resetting has been investigated during fictive locomotion in cats, its functional roles in
actual locomotion have not been clarified. Recently, simulation studies have been conducted to examine the roles of phase
resetting during human bipedal walking, assuming that locomotion is generated based on prescribed kinematics and feedback
control. However, such kinematically based modeling cannot be used to fully elucidate the mechanisms of adaptation. In this
article we proposed a more physiologically based mathematical model of the neural system for locomotion and investigated the
functional roles of phase resetting. We constructed a locomotor CPG model based on a two-layered hierarchical network model
of the rhythm generator (RG) and pattern formation (PF) networks. The RG model produces rhythm information using phase oscillators
and regulates it by phase resetting based on foot-contact information. The PF model creates feedforward command signals based
on rhythm information, which consists of the combination of five rectangular pulses based on previous analyses of muscle synergy.
Simulation results showed that our model establishes adaptive walking against perturbing forces and variations in the environment,
with phase resetting playing important roles in increasing the robustness of responses, suggesting that this mechanism of
regulation may contribute to the generation of adaptive human bipedal locomotion. |
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