During the last decade researchers have labored intensively to find new methods to photograph the complex networks of nerve cells that make up the brain and spinal cord, an attempt to overcome the severe limitations of earlier imaging technologies. The emerging science of connectomics, intended to map such connections, will be made possible by deploying these techniques.
In 2007 Jeff Lichtman, Joshua Sanes and colleagues at Harvard University came up with one of the most notable examples of the new brain-cell imaging methods. Brainbow lights up neurons in about 100 different hues, enabling a precise tracking of neural circuitry and synapses, the gaps between brain cells.
Scientists engineer a mouse or another model animal with a gene that randomly causes each neuron to express differing amounts of a red, green or blue fluorescent protein, producing a palette of varying pastel-like colors. Slices of tissue are photographed and recombined to produce detailed imagery of the brain’s structural topography. (The original discovery of what is called green fluorescent protein by Martin Chalfie, Osamu Shinomura and Roger Y. Tsien, from which these new multicolored fluorescent proteins are derived, was awarded the 2008 Nobel Prize in Chemistry.)