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The spinal generation of phases and cycle duration
Book chapter   Peer reviewed

The spinal generation of phases and cycle duration

Jean-Pierre Gossard, Jennifer Sirois, Patrick Noué, Marie-Pascale Côté, Ariane Ménard, Hugues Leblond and Alain Frigon
Progress in Brain Research, pp 15-29
2011
DOI: https://doi.org/10.1016/B978-0-444-53825-3.00007-3
PMID: 21333800
Featured in Collection :   UN Sustainable Development Goals @ Drexel

Abstract

CPG locomotion scratch sensory control spinal cord step cycle
During walking, an increase in speed is accompanied by a decrease in the stance phase duration while the swing phase remains relatively invariant. By definition, the rhythm generator in the lumbar spinal cord controls cycle period, phase durations, and phase transitions. Our first aim was to determine if this asymmetry in the control of locomotor cycles is an inherent property of the central pattern generator (CPG). We recorded episodes of fictive locomotion, that is, locomotor patterns in absence of reafference, in decerebrate cats with or without a complete spinal transection (acute or chronic). In fictive locomotion, stance and swing phases typically correspond to extension and flexion, respectively. In the vast majority of locomotor episodes, cycle period varied more with extensor phase duration. This could be observed without phasic sensory feedback or supraspinal structures or pharmacology. In a few experiments, we stimulated the mesencephalic locomotor region or selected peripheral nerves during fictive locomotion and both could alter the phase/cycle period relationship. We conclude that there is a built-in asymmetry within the spinal rhythm generator for locomotion, which can be modified by extraneous factors. Locomotor and scratching rhythms are characterized by alternation of flexion and extension phases within one hindlimb, which are mediated by rhythm-generating circuitry within the spinal cord. Our second aim was to determine if rhythm generators for locomotion and scratch have similar control mechanisms in adult decerebrate cats. The regulation of cycle period during fictive scratching was evaluated, as were the effects of specific sensory inputs on phase durations and transitions during pinna-evoked fictive scratching. Results show that cycle period during fictive scratching varied predominantly with flexion phase duration, contrary to spontaneous fictive locomotion. Ankle dorsiflexion greatly increased extension phase duration and cycle period during fictive locomotion but did not alter cycle period during scratching. These data indicate that cycle period, phase durations, and phase transitions are not regulated similarly during fictive locomotion and scratching, with or without sensory inputs, providing evidence for the existence of distinct interneuronal components of rhythm generation within the mammalian spinal cord.

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33 citations in Web of Science
28 citations in Scopus

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Collaboration types
Domestic collaboration
International collaboration
Web of Science research areas
Behavioral Sciences
Neurosciences
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