Mapping the frontiers of vision

Scientists at the Salk Institute for Biological Studies have developed new tools to chart the collections of neural circuits that determine what we see, a key step in revolutionizing research into the neurological basis of vision. For the first time, scientists created a neuron-by-neuron map of the regions of the mouse brain that process different kinds of visual information, laying the groundwork for decoding the circuitry of the brain using cutting-edge, genetic research techniques. The researchers injected mice with a calcium-sensitive fluorescent dye that glows when exposed to a certain light. The amount of calcium in nerve cells varies with the activity level of the neurons, so scientists measured the activity of brain cells based on how brightly they glowed when exposed to various visual stimuli. With these brain maps, researchers now have a baseline against which they can compare the brain function of mice with genetically manipulated neural function.