http://www.technologyreview.com/biomedicine/24870/?a=f

“Just five years ago, scientists at Stanford University discovered that neurons injected with a photo-sensitive gene from algae could be turned on or off with the flip of a light switch. This discovery has since turned hundreds of labs onto the young field of optogenetics. Today researchers around the world are using these genetic light switches to control specific neurons in live animals, observing their roles in a growing array of brain functions and diseases, including memory, addiction, depression, Parkinson’s disease, and spinal cord injury.”