title: Evidence for subjective values guiding posture and movement coordination in a free-endpoint whole-body reaching task.
abstract: When moving, humans must overcome intrinsic (body centered) and extrinsic (target-related) redundancy, requiring decisions when selecting one motor solution among several potential ones. During classical reaching studies the position of a salient target determines where the participant should reach, constraining the associated motor decisions. We aimed at investigating implicit variables guiding action selection when faced with the complexity of human-environment interaction. Subjects had to perform whole body reaching movements towards a uniform surface. We observed little variation in the self-chosen motor strategy across repeated trials while movements were variable across subjects being on a continuum from a pure 'knee flexion' associated with a downward center of mass (CoM) displacement to an 'ankle dorsi-flexion' associated with an upward CoM displacement. Two optimality criteria replicated these two strategies: a mix between mechanical energy expenditure and joint smoothness and a minimization of the amount of torques. Our results illustrate the presence of idiosyncratic values guiding posture and movement coordination that can be combined in a flexible manner as a function of context and subject. A first value accounts for the reach efficiency of the movement at the price of selecting possibly unstable postures. The other predicts stable dynamic equilibrium but requires larger energy expenditure and jerk.
authors.affiliation: INSERM-U1093, Action Cognition et Plasticité Sensorimotrice, Univ Bourgogne-Franche-Comté, Dijon, France.|Italian Institute of Technology CTNSC@UniFe (Center of Translational Neurophysiology for Speech and Communication) Via Fossato di Mortara, 17/19 - 44100 - Ferrara.
authors.forename: P M
authors.initials: PM
authors.lastname: Hilt
authors.affiliation: CIAMS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay Cedex, France.|CIAMS, Université d'Orléans, 45067, Orléans, France.
authors.forename: B
authors.initials: B
authors.lastname: Berret
authors.affiliation: INSERM-U1093, Action Cognition et Plasticité Sensorimotrice, Univ Bourgogne-Franche-Comté, Dijon, France.
authors.forename: C
authors.initials: C
authors.lastname: Papaxanthis
authors.affiliation: Neural Control of Movement Lab, School of Medicine, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, NSW, Australia.
authors.forename: P J
authors.initials: PJ
authors.lastname: Stapley
authors.affiliation: INSERM-U1093, Action Cognition et Plasticité Sensorimotrice, Univ Bourgogne-Franche-Comté, Dijon, France.|Department of Robotics, Brain and Cognitive Sciences, Istituto Italiano di Tecnologia, Genova, Italy.|Italian Institute of Technology CTNSC@UniFe (Center of Translational Neurophysiology for Speech and Communication) Via Fossato di Mortara, 17/19 - 44100 - Ferrara.|Institut Universitaire de France, Université de Bourgogne, Campus Universitaire, UFR STAPS Dijon, France.
authors.forename: T
authors.initials: T
authors.lastname: Pozzo
mesh_terms: D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D011187:Posture; D013647:Task Performance and Analysis; D055815:Young Adult