Their studies show that rewiring of the brain involves the formation and elimination of synapses, the connections between neurons. The technique offers a new way to examine how learning can spur changes in the organization of neuronal connections in the brain.

The researchers, postdoctoral fellow Josh Trachtenberg, graduate student Brian Chen and Karel Svoboda, a Howard Hughes Medical Institute investigator at Cold Spring Harbor Laboratory, published their findings in the December 19/26, 2002,issue of the journal Nature.

According to Svoboda, researchers had previously shown that the adult brain has a capacity to reorganize in response to new experience. However, it is not clear how this reorganization might occur. Svoboda and his colleagues wanted to see whether learning could induce restructuring of the neural circuitry in the brain that could not be picked up with conventional techniques.

To study those kinds of changes in a living animal, Svoboda and his colleagues started with transgenic mice that were engineered to produce green fluorescent protein within neurons in a portion of the brain that processes tactile sensory inputs from the whiskers. To observe changes in these neurons at high resolution, the scientists constructed a 2-photon laser scanning microscope. This microscope uses an infrared laser to excite green fluorescent protein in neurons, deep in the brain, through a tiny glass window installed in a portion of the mouse's skull.

"Since we had this great tool to look at the brain at unprecedented resolution we did not know what to expect and we began with no preconceived notions of what we might see in these animals," said Svoboda. "
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Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
18-Dec-2002