Ron
Harris-Warrick |
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The Harris-Warrick lab is studying the cellular and molecular mechanisms underlying the modulation of activity of small neural networks in the stomatogastric ganglion of crustacea. These circuits, called central pattern generators, generate the sequences of commands for simple rhythmic movements. Neuromodulators such as amines or peptides affect the neurons in the circuits by changing their intrinsic electrophysiological firing properties and by modifying the strength of their synaptic interactions. This allows the moment-by-moment construction of new functional circuits from the anatomical network of available neurons, thus generating many variants on the basic theme of the movement. The lab is presently analyzing the effects of serotonin, dopamine and octopamine on the pyloric motor circuit of the lobster stomatogastric ganglion. This circuit contains only 14 neurons, each of which can be unambiguously identified in experiments. Our work involves several different levels of analysis, including: 1) physiological and biophysical studies of the ionic currents modified by amines in each identified neuron, and correlation with its changes in firing patterns; 2) identification and study of the neurons that normally release these amines, to put their activity into a proper behavioral context; 3) mathematical modeling of the intrinsic firing properties of single neurons and small networks, using the tools of dynamical systems analysis and bifurcation theory. In a second project, the lab has cloned lobster homologues of the four members of the Shaker family of voltage-dependent K+ channe genes, and is expressing them in Xenopus oocytes to study their properties and compare them to endogenous currents in identified neurons. They have also developed in situ hybridization and quantitative single cell PCR methods to map the level of expression of these 4 genes in single identified neurons in the pyloric network, with the goal of understanding the physiological roles of each gene in this small network. The eventual goal of the lab is to bridge the gap between biophysics and behavior and to show how modulator-induced changes in neuronal activity at the channel level can lead to detectable changes in behavior.
updated 9/15/06 - Suzanne Aceti Koehl