Neuron
Volume 91, Issue 3, 3 August 2016, Pages 615-628
Journal home page for Neuron

Article
Selective Inhibition Mediates the Sequential Recruitment of Motor Pools

https://doi.org/10.1016/j.neuron.2016.06.031Get rights and content
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Highlights

  • Drosophila larval muscles are sequentially recruited during locomotion

  • Motor neuron intrinsic properties do not determine order of recruitment

  • EM reconstructions reveal divergent premotor networks of two sequential motor pools

  • A GABA+ neuron acts as a delay line mediating delayed motor pool activation

Summary

Locomotor systems generate diverse motor patterns to produce the movements underlying behavior, requiring that motor neurons be recruited at various phases of the locomotor cycle. Reciprocal inhibition produces alternating motor patterns; however, the mechanisms that generate other phasic relationships between intrasegmental motor pools are unknown. Here, we investigate one such motor pattern in the Drosophila larva, using a multidisciplinary approach including electrophysiology and ssTEM-based circuit reconstruction. We find that two motor pools that are sequentially recruited during locomotion have identical excitable properties. In contrast, they receive input from divergent premotor circuits. We find that this motor pattern is not orchestrated by differential excitatory input but by a GABAergic interneuron acting as a delay line to the later-recruited motor pool. Our findings show how a motor pattern is generated as a function of the modular organization of locomotor networks through segregation of inhibition, a potentially general mechanism for sequential motor patterns.

Cited by (0)

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Co-senior author

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Present address: School of Psychology and Neuroscience, University of St Andrews, St Andrews KY16 9JP, UK

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Present address: Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA