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A central pattern generator producing alternative outputs: phase relations of leech heart motor neurons with respect

Brian J Norris1, Adam L Weaver, Angela Wenning

  • 1Department of Biology, Emory University, Atlanta, GA 30322, USA.

Journal of Neurophysiology
|August 31, 2007
PubMed

Insights

Leech heartbeat central pattern generators (CPGs) create asymmetric motor patterns. This study maps neural coordination, revealing stereotypical midbody motor neuron activity during peristaltic heartbeats.

Area of Science:

  • Neuroscience
  • Animal Physiology
  • Biophysics

Background:

  • The leech heartbeat central pattern generator (CPG) involves identified interneurons controlling motor neurons.
  • CPGs generate rhythmic motor patterns, but coordination mechanisms remain complex.
  • Leech hearts exhibit synchronous and peristaltic constriction patterns, reflecting underlying neural asymmetry.

Purpose of the Study:

  • To elucidate the neural basis of asymmetric intersegmental coordination in the leech heartbeat CPG.
  • To map the phase relationships between premotor interneurons and motor neurons in different coordination modes.
  • To identify the most stereotypical features of the fictive motor pattern across individual leeches.

Main Methods:

  • Extracellular recordings of motor neuron activity in 61 isolated leech nerve cords.
  • Simultaneous recording of premotor heart interneurons, including the phase reference HN(4).
  • Integration of recorded data with existing descriptions of premotor interneuron activity patterns.

Main Results:

  • The CPG generates stereotypical side-to-side asymmetric coordination patterns in motor neurons.
  • These motor patterns directly reflect the asymmetric activity of premotor interneurons.
  • Midbody intersegmental phase progression during peristaltic coordination is highly stereotypical.

Conclusions:

  • The study provides a comprehensive phase diagram of the leech heartbeat CPG motor ensemble.
  • Asymmetric coordination is a fundamental feature of leech heart motor control.
  • The findings offer insights into the robustness and variability of neural pattern generation.

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