title: Speed dependency in α-motoneuron activity and locomotor modules in human locomotion: indirect evidence for phylogenetically conserved spinal circuits.
abstract: Coordinated locomotor muscle activity is generated by the spinal central pattern generators (CPGs). Vertebrate studies have demonstrated the following two characteristics of the speed control mechanisms of the spinal CPGs: (i) rostral segment activation is indispensable for achieving high-speed locomotion; and (ii) specific combinations between spinal interneuronal modules and motoneuron (MN) pools are sequentially activated with increasing speed. Here, to investigate whether similar control mechanisms exist in humans, we examined spinal neural activity during varied-speed locomotion by mapping the distribution of MN activity in the spinal cord and extracting locomotor modules, which generate basic MN activation patterns. The MN activation patterns and the locomotor modules were analysed from multi-muscle electromyographic recordings. The reconstructed MN activity patterns were divided into the following three patterns depending on the speed of locomotion: slow walking, fast walking and running. During these three activation patterns, the proportion of the activity in rostral segments to that in caudal segments increased as locomotion speed increased. Additionally, the different MN activation patterns were generated by distinct combinations of locomotor modules. These results are consistent with the speed control mechanisms observed in vertebrates, suggesting phylogenetically conserved spinal mechanisms of neural control of locomotion.
authors.affiliation: Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan.|Department of Rehabilitation for the Movement Functions, Research Institute of National Rehabilitation Center for the Disabled, Saitama, Japan.|Japan Society for the Promotion of Science, Tokyo, Japan.
authors.forename: Hikaru
authors.identifier: http://orcid.org/0000-0001-6027-3869
authors.initials: H
authors.lastname: Yokoyama
authors.affiliation: Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Ogawa
authors.affiliation: Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Shinya
authors.affiliation: Department of Rehabilitation for the Movement Functions, Research Institute of National Rehabilitation Center for the Disabled, Saitama, Japan.
authors.forename: Noritaka
authors.initials: N
authors.lastname: Kawashima
authors.affiliation: Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan nakazawa@idaten.c.u-tokyo.ac.jp.
authors.forename: Kimitaka
authors.initials: K
authors.lastname: Nakazawa
mesh_terms: D006801:Humans; D008124:Locomotion; D009046:Motor Neurons / Q000502:physiology*; D012420:Running; D013116:Spinal Cord / Q000502:physiology*; D016138:Walking
keywords: central pattern generators; locomotion; locomotor module; muscle synergy; spinal cord