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Control of locomotor cycle durations.
S Yakovenko1, D A McCrea, K Stecina
1Department of Physiology, Universite de Montreal, Montreal, Quebec, Canada.
Journal of Neurophysiology
|April 1, 2005
Summary
Locomotion speed control is flexible. In cats, changes in flexor phase duration, not extensor, primarily alter step cycle timing during fictive locomotion, challenging previous assumptions about the locomotor central pattern generator (CPG).
Area of Science:
- Neuroscience
- Locomotion Biomechanics
- Motor Control
Background:
- Locomotion speed increases typically correlate with shorter step cycles.
- Previous research suggested the locomotor central pattern generator (CPG) achieves this by shortening extensor phases.
Purpose of the Study:
- To investigate the phase duration control mechanisms in the locomotor CPG.
- To determine if the CPG has an inherent bias towards flexor or extensor phases.
Main Methods:
- Fictive locomotion was induced via midbrain locomotor region (MLR) stimulation in cats.
- Spontaneous variations in step cycle duration were analyzed.
- A half-center oscillator model was used to fit experimental data.
Main Results:
- In most experiments (22/31), spontaneous cycle duration changes were mainly due to flexor phase variations.
- The locomotor CPG demonstrated no inherent bias towards flexor or extensor phases.
- A half-center oscillator model with 'bias' and 'gain' parameters successfully fitted the data.
Conclusions:
- Locomotor phase durations exhibit significant flexibility in MLR-induced fictive locomotion.
- Background drive to neural timing elements likely determines which phase (flexor or extensor) is dominant.
- Sensory input and central drive interact to regulate locomotor phase durations.