I've got an article in tomorrow's New York Times about a startling new way to control the nervous system of animals. Scientists at Yale have genetically engineered flies with neurons that grow light-sensitive triggers. Shine a UV laser at the flies, and the neurons switch on. In one experiment, the scientists were able to make decapitated flies leap into the air by triggering escape-response neurons. In another, they put the trigger in dopamine-producing neurons, and the flash sent healthy flies walking madly around their dish. (You can read the paper for free at Cell's web site.)
In working on this story, I was reminded of the research being done now with implanted electrodes, which I wrote about last year in Popular Science. Much of this research focuses on listening in on neurons to control robots or computers. But the electrodes have also been used to send electricity into the brain to control an animal. In one case, scientists steered a rat by sending jolts into its brain.
But those who feel anxious about the genetic engineering I write about tomorrow should bear a couple things in mind. First off all, this method only lets scientists turn on an entire type of neurons. All the escape-response neurons became active in the first experiment. All the dopamine-producing neurons became active in the second. That's a far cry from a complex set of signals that might make an animal carry out a complex behavior. But that's not what the scientists who designed this new method had in mind, anyway. They want to develop new ways to do experiments on the nervous system.
Still, science fiction writers should pay heed. It's conceivable, for example, that a completely unethical scientist could engineer similar triggers into a human brain (although it could also fail completely). And another thing that inspires the sci-fi imagination is the experiment on dopamine-producing neurons. Dopamine is a neurotransmitter that give the brain a sense of expectation and anticipation, priming it to learn how to gain rewards. It's also what cocaine exploits to produce its addictive pleasure. In other words, when the scientists switched on their laser, the flies got the biggest high of their lives.