Medtronic scientists emphasize the very early nature of the device. "This is research for use with animal models and not ready for any kind of human translation currently," emphasizes Denison. Still, he continues: "What's exciting is that therapies today remain based on these electrically based ideas from the 19th century. Now this novel, disruptive technology offers a unique interface to the nervous system."

Today, over 500 laboratories are applying optogenetic tools to animal models of Parkinson's, blindness, spinal injury, depression, narcolepsy, addiction, and memory. Medtronic, which has built its business by pioneering market implementation of medical research, has consulted extensively with optogenetic pioneers Karl Deisseroth of Stanford and Ed Boyden of MIT to build an implant to support this new science. (Boyden is an occasional columnist for Technology Review.)

In order to transform the research implant into a clinical device, Medtronic or others will need to find ways to safely deliver the necessary genes to specific neural circuits in the brain. Denison says he thinks that development of practical optogenetic-based therapies for human patients will be gradual. "Frankly, this is a technology I can see my son working on as a Medtronic employee," he says.

MIT's Boyden, however, envisions a more accelerated development: "I think it's more in the three- to 10-year span," he says. Boyden has cofounded a company, Eos, to develop gene therapies to cure blindness. (Because it targets the eye, this therapy would not require an implant.) Jerry Silver of Case-Western University has a startup, LucCell, that aims at such therapies to restore damaged spinal cord function. "Gene therapy is a maturing field," says Silver. "There's a virus type called AAV --adeno-associated virus--that is natural, that almost all of us already carry, that has no symptoms, and that already has been used in many hundreds of patients without a single serious adverse event."

Overall, Boyden concludes: "In many neural or psychiatric disorders, a very small fraction of brain cells have very big alterations --Parkinson's is the death of perhaps a few thousand cells. If with optogenetics you can correct those downstream targets without altering all the 'normal neurons'--in quotes--you could solve our present problem, which is that every drug for treating brain disorders has very serious side-effects and neural implants are extremely blunt instruments. So that's the hope."