A technique that combines a laser beam with a multiphoton microscope allows scientists to quickly observe the function of neurons, or nerve cells, in three dimensions, providing a much better view of their fast activity.Scientists at Baylor College of Medicine (BCM) in Houston used a multiphoton microscope, which looks at tissues in different optical planes, albeit very slowly, and adapted a fast-moving laser beam to work with the microscope to quickly observe neurons from all sides. “Most microscopes can only study cell function in two dimensions,” said Dr. Gaddum Duemani Reddy, an MD/PhD student at BCM and Rice University in Houston. He is first author of a paper on the work appearing in the current issue of the journal Nature Neuroscience. “To look at different planes, you have to move your preparation (of cells) or the objective lens. That takes time, and we are looking at processes that happen in milliseconds.” To solve that problem, he said, they developed a “trick” to quickly move a laser beam in three dimensions and then adapted that laser beam to the multiphoton microscope they were using. That allowed them to “see” the neuron’s function in 3-D. A multiphoton microscope looks much like a conventional, upright microscope but it has an adaption that allows it to look at tissues in sections. A conventional multiphoton microscope does that very slowly, he said. “With ours, you can do it very quickly. We are starting to see how a single neuron behaves in our laboratory,” he said. The next step will be to use to it to look a clusters or colonies of neurons. This will enable them to actually see the neuronal interactions, he said. “At present, the technology is applied in my lab to study information processing of single neurons in brain slice preparations by 3-D multisite optical recording,” said Dr. Peter Saggau, professor of neuroscience at BCM and the paper’s senior author. He is collaborating with two other labs on using the technology in other ways. In one, he said, researchers plan to use the technology to monitor nerve activity in the brains of lab animals in order study how populations of neurons communicate during visual stimulation. Another study attempts to use the technology to monitor stimulation of the acoustic nerve optically. Those scientists hope to reinstate hearing in lab animals whose inner ear receptors do not work. Keith Kelleher of the University of Houston and Rudy Fink of BCM also took part in the research, which was funded by the National Institutes of Health and the National Science Foundation. For more information, visit: www.bcm.edu