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Author Notes:

Correspondence: Ronald L. Calabrese, Department of Biology, Emory University, 1510 Clifton Road N.E., Atlanta, GA 30322, USA. Email: ronald.calabrese@emory.edu

Acknowledgments: We thank Jesse Hanson and Anne-Elise Tobin for discussions on how best to implement the genetic algorithm for fitting the switch interneuron model.

We also thank Dr. Angela Wenning for countless critical discussions and help with data analysis and figure preparation.

Edited by: Kathleen A. French, University of California San Diego, USA

Reviewed by: Michael Nussbaum, University of Pennsylvania, USA; William Kristan, University of California San Diego, USA

Disclosures: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Research Funding:

This work was supported by the NIMH APA DPN predoctoral fellowship 5 T06 MH to Rebecca C. Roffman, NIH Postdoctoral Fellowship Grant GM00680 to Adam L. Weaver and by NIH Grant NS24072 to Ronald L. Calabrese.


  • neuronal networks
  • entrainment
  • neuronal oscillators

A role for compromise: synaptic inhibition and electrical coupling interact to control phasing in the leech heartbeat CPG


Journal Title:

Frontiers in Behavioral Neuroscience


Volume 4, Number 38


, Pages 1-17

Type of Work:

Article | Final Publisher PDF


How can flexible phasing be generated by a central pattern generator (CPG)? To address this question, we have extended an existing model of the leech heartbeat CPG's timing network to construct a model of the CPG core and explore how appropriate phasing is set up by parameter variation. Within the CPG, the phasing among premotor interneurons switches regularly between two well defined states – synchronous and peristaltic. To reproduce experimentally observed phasing, we varied the strength of inhibitory synaptic and excitatory electrical input from the timing network to follower premotor interneurons. Neither inhibitory nor electrical input alone was sufficient to produce proper phasing on both sides, but instead a balance was required. Our model suggests that the different phasing of the two sides arises because the inhibitory synapses and electrical coupling oppose one another on one side (peristaltic) and reinforce one another on the other (synchronous). Our search of parameter space defined by the strength of inhibitory synaptic and excitatory electrical input strength led to a CPG model that well approximates the experimentally observed phase relations. The strength values derived from this analysis constitute model predictions that we tested by measurements made in the living system. Further, variation of the intrinsic properties of follower interneurons showed that they too systematically influence phasing. We conclude that a combination of inhibitory synaptic and excitatory electrical input interacting with neuronal intrinsic properties can flexibly generate a variety of phase relations so that almost any phasing is possible.

Copyright information:

© 2010 Weaver, Roffman, Norris and Calabrese. This is an open-access article subject to an exclusive license agreement between the authors and the Frontiers Research Foundation, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are credited. - See more at: http://journal.frontiersin.org/Journal/10.3389/fnbeh.2010.00038/full#sthash.eDTqx1cW.dpuf

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