title: Sensorimotor control of gait: a novel approach for the study of the interplay of visual and proprioceptive feedback.
abstract: Sensorimotor control theories propose that the central nervous system exploits expected sensory consequences generated by motor commands for movement planning, as well as online sensory feedback for comparison with expected sensory feedback for monitoring and correcting, if needed, ongoing motor output. In our study, we tested this theoretical framework by quantifying the functional role of expected vs. actual proprioceptive feedback for planning and regulation of gait in humans. We addressed this question by using a novel methodological approach to deliver fast perturbations of the walking surface stiffness, in conjunction with a virtual reality system that provided visual feedback of upcoming changes of surface stiffness. In the "predictable" experimental condition, we asked subjects to learn associating visual feedback of changes in floor stiffness (sand patch) during locomotion to quantify kinematic and kinetic changes in gait prior to and during the gait cycle. In the "unpredictable" experimental condition, we perturbed floor stiffness at unpredictable instances during the gait to characterize the gait-phase dependent strategies in recovering the locomotor cycle. For the "unpredictable" conditions, visual feedback of changes in floor stiffness was absent or inconsistent with tactile and proprioceptive feedback. The investigation of these perturbation-induced effects on contralateral leg kinematics revealed that visual feedback of upcoming changes in floor stiffness allows for both early (preparatory) and late (post-perturbation) changes in leg kinematics. However, when proprioceptive feedback is not available, the early responses in leg kinematics do not occur while the late responses are preserved although in a, slightly attenuated form. The methods proposed in this study and the preliminary results of the kinematic response of the contralateral leg open new directions for the investigation of the relative role of visual, tactile, and proprioceptive feedback on gait control, with potential implications for designing novel robot-assisted gait rehabilitation approaches.
authors.affiliation: Human-Oriented Robotics and Control Lab, School for Engineering of Matter Transport and Energy, Arizona State University Tempe, AZ, USA.
authors.forename: Ryan
authors.initials: R
authors.lastname: Frost
authors.affiliation: Human-Oriented Robotics and Control Lab, School for Engineering of Matter Transport and Energy, Arizona State University Tempe, AZ, USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Skidmore
authors.affiliation: Neural Control of Movement Laboratory, School of Biological and Healthy Systems Engineering, Arizona State University Tempe, AZ, USA.
authors.forename: Marco
authors.initials: M
authors.lastname: Santello
authors.affiliation: Human-Oriented Robotics and Control Lab, School for Engineering of Matter Transport and Energy, Arizona State University Tempe, AZ, USA.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Artemiadis
keywords: gait; gait rehabilitation; proprioceptive feedback; rehabilitation robotics; visual feedback