My lab studies how networks of nerve cells produce different behaviors and how these neuronal networks are established during embryogenesis. We use electrophysiological, imaging, anatomical, computational, and embryological techniques to characterize these circuits in the relatively tractable nervous system of the medicinal leech, and construct computerized models of them. One behavior, local bending, is produced by a distributed network that we have used to study vector calculations, coding/decoding, and control of gain. Two other behaviors, swimming and crawling, use overlapping networks of neurons. We have found, remarkably, that interneurons are used in multiple behaviors to make decisions about which behavior to produce. We use voltage-sensitive to identifying neurons involved in different behaviors, for monitoring the activity of many interneurons at once, and for determining the connections among the neurons involved in the various behaviors. We also study the mechanisms by which these neuronal networks are established during embryogenesis. We are testing several mechanisms that have been proposed for how the neuronal connections form. For instance, we can show that knocking down the expression of gap junction molecules just before chemical synapses form keeps the chemical synapses from forming for the life of the animal. These studies will also help us to understand how particular kinds of neuronal connections are used to put together different behavioral circuits.
Briggman, K.L., Abarbanel, H.D.I., & Kristan, W.B., Jr. (2005) Optical imaging of neuronal populations during decision-making. Science 307: 896-901.
Baca, S.M., Thomson, E.E., & Kristan, W.B. (2005) Location and intensity discrimination in the leech local bending response quantified using optic flow and principal components analysis. J. Neurophysiol. 93:3560-72.
Marin-Burgin, A., Eisenhart, J.F., Baca, S.M., Kristan, W.B. Jr., & French, K.A. (2005) Sequential development of electrical and chemical synaptic connections generates a specific behavioral circuit in the leech. J. Neurosci 25:2478-89.
Kristan, W.B., Jr., Calabrese, R.L., and Friesen, W.O., (2005) Neuronal basis of leech behaviors. Prog. Neurobiol. 76:279-327.
Thomson E.E., Kristan W.B. (2006) Encoding and decoding touch location in the leech CNS. J Neurosci 26:8009-16.
Briggman, K.L., Kristan, W.B., Jr. (2006) Imaging dedicated and multifunctional neural circuits generating distinct behaviors. J Neurosci 26:10925-33.