The first demonstration of the new technique, reported as the cover story in the Jan. 28, 2004, issue of The Journal of Neuroscience , was in neurons of the lowly sea slug, Aplysia . But the Cornell researchers anticipate that eventually the technique will be used in brain tissues of higher animals and could help decipher the wiring of the brain and possibly explain consequences of degenerative brain diseases such as Alzheimer's.
"This technique gives us the ability to look at membrane potential in nerve-cell signaling with high resolution deep in intact tissue, where previous methods were not applicable," says Daniel A. Dombeck, lead author on the journal paper and a graduate student in the Developmental Resource for Biophysical Imaging Opto-Electronics laboratory of Watt W. Webb, professor of applied physics at Cornell.
"With submillisecond resolution, we're beginning to see how much the electrical signals can vary between different places of a single neuron," says Dombeck. "With further development, we should be able to see how pathology affects electrical signals. We'd like to know, for example, how much Alzheimer's plaques affect the signal transmission in axons."
Multiphoton microscopy, including second-harmonic generation, produces high-resolution, three-dimensional pictures of tissue with minimal damage to living cells, using a laser that produces a stream of extremely short, intense pulses. When two or three photons strike a biological molecule at the same time, their energies combine. This has the cumulative effect of delivering one photon -- with nearly twice the energy -- to the sample. By adjusting
Contact: Roger Segelken
Cornell University News Service