One of the fundamental problems in neuroscience is understanding how circuit function arises from the intrinsic properties of individual neurons and their synaptic connections. Of particular interest to us today is the extent to which similar circuit outputs can be generated by multiple mechanisms, both in different individual animals, or in the same animal over its life-time. As an experimental preparation we exploit the advantages of the central pattern generating circuits in the crustacean stomatogastric nervous system. Central pattern generators are groups of neurons found in vertebrate and invertebrate nervous systems responsible for the generation of specific rhythmic behaviors such as walking, swimming, and breathing. The central pattern generators in the stomatogastric ganglion (STG) of lobsters and crabs are ideal for many analyses because the STG has only about 30 large neurons, the connectivity is established, the neurons are easy to record from, and when the stomatogastric ganglion is removed from the animal, it continues to produce rhythmic motor patterns.
Work in the lab centers on three main questions:
- How do neuromodulators and neuromodulatory neurons reconfigure circuits so that the same group of neurons can produce a variety of behaviorally relevant outputs?
- How can networks be both stable over the lifetime of the animal despite ongoing turnover of membrane proteins such as channels and receptors? How is network stability maintained over long time periods? To what extent do similar network outputs result from different underlying mechanisms or solutions?.
- How variable are the sets of parameters that govern circuit function across animals? How can animals with disparate sets of circuit parameters respond reliably to perturbations such as neuromodulators and temperature?
To address these questions we employ electrophysiological, biophysical, computational, anatomical, biochemical, and molecular techniques.
A) A schematic drawing of the entire stomatogastric nervous system including the stomatogastric ganglion (STG). B) Spontaneous electrical activity of the pyloric central pattern generator of the STG. C) A schematic wiring diagram showing the synaptic connectivity of the pyloric neurons within the STG.
The ongoing electrical activity within the STG is altered by the presence of neurohormones delivered by the circulatory system (left) as well as the local release of neuromodulators from projection neurons (right). While neuromodulators are present and critically important in many biological systems, the role of neuromodulators in shaping network output is most concretely understood in simple systems, such as the stomatogastric nervous system.