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November 30, 2006


Biology Professor Wins NSF Grant to Study
the Stop and Go of Rhythmic Behavior

Brodfuehrer holding leech
Brodfuehrer with research subject

What happens in neurons to trigger — and stop — complex behavior patterns like walking? With a grant of $159,394 from the National Science Foundation, Professor of Biology Peter Brodfuehrer hopes to shed some light on the initiation and termination of rhythmic movements of all sorts by investigating one of the simplest examples of it: swimming in the medicinal leech.

"Leech swimming is much less complicated than, for instance, walking in a vertebrate," Brodfuehrer explains. "The leech is a segmented worm, with basically the same body plan as an earthworm. In a segmented animal, the nervous system in each segment is approximately the same as the nervous system in the next segment, so that if you understand how one segment works, you more or less have an understanding of them all. This makes swimming in the leech, which has a total of about 2,000 neurons, much easier to study than walking in humans, who have more than 100 billion neurons in their brains."

Nevertheless, Brodfuehrer says, the leech is still a good model for understanding much more complex behavior patterns in much more complex animals.

"We know from many previous studies that a neuron in the leech works basically the same way as a neuron in other animals. In the leech, there is a neural network that changes unorganized input into coordinated output; we call that a central pattern generator. There is an awful lot of evidence across different species that the same set of fundamental rules governs these networks, so if you look at a simple network, you get insight into how a more complex network operates."

Brodfuehrer and other scientists have identified what sorts of neurons are involved in the leech's pattern generator and on some levels how they communicate. Certain cells, he says, will trigger complex behavior events when stimulated.

"But those triggers are just that. They are not really involved in determining how long the event lasts or in stopping it. If you stimulate a certain cell and cause a leech to swim, it will eventually stop swimming. We want to investigate what intrinsic mechanism within the network enables the termination of the behavior pattern."

The grant will fund collaborative research with two scientists at the University of Virginia: Professor of Biology Otto Friesen, who directed Brodfuehrer's dissertation, and John T. Hackett, a professor of molecular physiology and biological physics at the University of Virginia School of Medicine.

"One aspect of the grant that I find most appealing for Bryn Mawr undergraduates is the opportunity to perform summer research in either Otto's or John's lab," Brodfuehrer says. "This is fully funded by the grant and is an excellent opportunity for someone at a small liberal-arts college to get the feel of a research experience at a major research institution."

Undergraduate research associates will learn to isolate the animals' nervous systems, to use modern electrophysiological recording techniques to acquire data, and to analyze their findings, "which are skills that will directly benefit them as they pursue careers in science," Brodfuehrer points out. Brodfuehrer and his colleagues also plan to use the proposed experiments to develop laboratory exercises that will be incorporated into advanced neurobiology courses at both Bryn Mawr and the University of Virginia.


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