Intercircuit control via rhythmic regulation of projection neuron activity

Debra E. Wood, Yair Manor, Farzan Nadim, Midlael P. Nusbaum

Research output: Contribution to journalArticlepeer-review

39 Scopus citations


Synaptic feedback from rhythmically active neuronal circuits commonly causes their descending inputs to exhibit the rhythmic activity pattern generated by that circuit. In most cases, however, the function of this rhythmic feedback is unknown. In fact, generally these inputs can still activate the target circuit when driven in a tonic activity pattern. We are using the crab stomatogastric nervous system (STNS) to test the hypothesis that the neuronal circuit-mediated rhythmic activity pattern in projection neurons contributes to intercircuit regulation. The crab STNS contains an identified projection neuron, modulatory commissural neuron 1 (MCN1), whose tonic stimulation activates and modulates the gastric mill (chewing) and pyloric (filtering of chewed food) motor circuits in the stomatogastric ganglion (STG). During tonic stimulation of MCN1, the pyloric circuit regulates both gastric mill cycle frequency and gastropyloric coordination via a direct synapse onto a gastric mill neuron in the STG. However, when MCN1 is spontaneously active, it has a pyloric-timed activity pattern attributable to synaptic input from the pyloric circuit. This pyloric-timed activity in MCN1 provides the pyloric circuit with a second pathway for regulating the gastric mill rhythm. At these times, the direct STG synapse from the pyloric circuit to the gastric mill circuit is not necessary for pyloric regulation of the gastric mill rhythm. However, in the intact system, these two pathways play complementary roles in this intercircuit regulation. Thus, one role for rhythmicity in modulatory projection neurons is to enable them to mediate the interactions between distinct but related neuronal circuits.

Original languageEnglish (US)
Pages (from-to)7455-7463
Number of pages9
JournalJournal of Neuroscience
Issue number34
StatePublished - Aug 25 2004

All Science Journal Classification (ASJC) codes

  • General Neuroscience


  • Central pattern generator
  • Gastric mill circuit
  • Modulatory projection neuron
  • Neuromodulation
  • Pyloric circuit
  • Stomatogastric ganglion


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