title: Proprioceptive feedback in humans expresses motor invariants during writing.
abstract: Proprioceptive feedback from populations of muscle spindle afferents feeds the brain with information relating to the instantaneous velocity and direction of ongoing movements. In this paper, we investigate whether the invariant relationship between the velocity and curvature of a trajectory, i.e. the two-thirds power law, is reflected in this muscle spindle feedback. Sixty unitary muscle spindle afferents from six ankle muscle groups were recorded using intraneural microelectrodes during imposed "writing-like" movements. The movements had kinematic parameters obeying the two-thirds power law and were imposed so that the tip of the foot followed trajectories forming four different letters and six numbers. The responses of the muscle spindle afferent populations were analysed using the population vector model. The results demonstrate that the neuronal trajectories attained from populations of muscle spindles clearly depict the path and kinematic parameters and express the movement invariants, i.e. the trajectory segmentation into units of action and the two-thirds power law. The central vs peripheral origin of such constraints involved in the motor system is discussed.
authors.affiliation: Laboratoire de Neurobiologie Humaine, UMR 6149, Université de Provence CNRS, Centre St-Charles, 3, place Victor Hugo, 13331, Marseille Cedex 03, France. albert-f@up.univ-mrs.fr
authors.forename: Frederic
authors.initials: F
authors.lastname: Albert
authors.forename: Edith
authors.initials: E
authors.lastname: Ribot-Ciscar
authors.forename: Michel
authors.initials: M
authors.lastname: Fiocchi
authors.forename: Mikael
authors.initials: M
authors.lastname: Bergenheim
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Roll
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000344:Afferent Pathways / Q000502:physiology; D000843:Ankle Joint / Q000502:physiology; D001696:Biomechanical Phenomena; D004576:Electromyography; D005246:Feedback / Q000502:physiology*; D005528:Foot / Q000294:innervation / Q000502:physiology; D006801:Humans; D009048:Motor Skills / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D009470:Muscle Spindles / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D009475:Neurons, Afferent / Q000502:physiology; D011434:Proprioception / Q000502:physiology*