Institut de Neurosciences Cognitives et Intégratives d'Aquitaine (UMR5287)

Aquitaine Institute for Cognitive and Integrative Neuroscience



INCIA - UMR 5287- CNRS
Université de Bordeaux

Zone nord Bat 2 2ème étage
146, rue Léo Saignat
33076 Bordeaux cedex
France

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Synergistic interaction between sensory inputs and propriospinal signalling underlying quadrupedal locomotion

by Loïc Grattier - published on

Synergistic interaction between sensory inputs and propriospinal signalling underlying quadrupedal locomotion
Marie Boulain, Inès Khsime, Mélissa Sourioux, Muriel Thoby-Brisson, Grégory Barrière, John Simmers, Didier Morin, Laurent Juvin

J Physiol . 2021 Aug 19. doi: 10.1113/JP281861. Online ahead of print.
https://physoc.onlinelibrary.wiley.com/doi/10.1113/JP281861


Abstract

Quadrupedal locomotion relies on a dynamic coordination between central pattern generators (CPGs) located in the cervical and lumbar spinal cord, and controlling the fore- and hindlimbs, respectively. It is assumed that this CPG interaction is achieved through separate closed-loop processes involving propriospinal and sensory pathways. However, the functional consequences of a concomitant involvement of these different influences on the degree of coordination between the fore- and hindlimb CPGs is still largely unknown. Using an in vitro brainstem/spinal cord preparation of neonatal rat, we found that rhythmic, bilaterally alternating stimulation of hindlimb sensory input pathways elicited coordinated hindlimb and forelimb CPG activity. During pharmacologically induced fictive locomotion, lumbar dorsal root (DR) stimulation entrained and stabilized an ongoing cervico-lumbar locomotor-like rhythm and increased the amplitude of both lumbar and cervical ventral root bursting. The increase in cervical burst amplitudes was correlated with the occurrence of doublet action potential firing in a subpopulation of motoneurons, enabling the latter to transition between low and high frequency discharge according to the intensity of DR stimulation. Moreover, our data revealed that propriospinal and sensory pathways act synergistically to strengthen cervico-lumbar interactions. Indeed, split-bath experiments showed that fully coordinated cervico-lumbar fictive locomotion was induced by combining pharmacological stimulation of either the lumbar or cervical CPGs with lumbar DR stimulation. This study thus highlights the powerful interactions between sensory and propriospinal pathways which serve to ensure the coupling of the fore- and hindlimb CPGs for effective quadrupedal locomotion.