Neural circuits coordinate with muscles and sensory feedback to generate motor behaviors appropriate to an animal’s environment. In C. elegans, the mechanisms by which the motor circuit generates undulations and modulates them based on the environment are largely unclear. We quantitatively analyzed C. elegans locomotion during free movement and during transient optogenetic muscle inhibition. Undulatory movements were highly asymmetrical with respect to the duration of bending and unbending during each cycle. Phase response curves induced by brief optogenetic inhibition of head muscles showed gradual increases and rapid decreases as a function of phase at which the perturbation was applied. A relaxation oscillator model based on proprioceptive thresholds that switch the active muscle moment was developed and is shown to quantitatively agree with data from free movement, phase responses, and previous results for gait adaptation to mechanical loadings. Our results suggest a neuromuscular mechanism underlying C. elegans motor pattern generation within a compact circuit.
All data and software have been deposited to a Dryad repository.
- Hongfei Ji
- Anthony D Fouad
- Christopher Fang-Yen
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Manuel Zimmer, University of Vienna, Austria
- Received: April 29, 2021
- Accepted: September 24, 2021
- Accepted Manuscript published: September 27, 2021 (version 1)
© 2021, Ji et al.
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