© Scott Camazine/Science Photo Library
Short of sticking electrodes directly into an organism's brain, scientists looking to image neural signaling in living systems have few options. Until recently, most researchers made do with voltage- or calcium-sensitive organic dyes.
The use of green fluorescent protein (GFP) by scientists in Roger Tsien's lab at the University of California, San Diego, in the early 1990s marked a turning point for the field. By fusing GFP to a gene whose product is sensitive to changes in neural activity – for instance, fluctuations in calcium ion concentration or membrane voltage – scientists could target the probes to specific populations of neurons and read these changes optically.
"This is such a wonderful technique to be able to use. It's such a wonderful fusion of traditional observational anatomy and electrophysiology and molecular reductionist understanding of how the brain works," says neuroscientist Alison Barth of Carnegie Mellon University ...
