Laser light stimulation to a portion of the brain can wipe away addictive behaviors – or conversely turn on a drug addiction, a new US study on rats has demonstrated. An estimated 1.4 million Americans are addicted to cocaine, and cocaine abuse is a main cause of heart attacks and strokes for people under 35. The drug addiction places a heavy toll on society in terms of lost job productivity, lost earnings, cocaine-related crime, incarcerations, and treatment and prevention programs. “When we turn on a laser light in the prelimbic region of the prefrontal cortex, the compulsive cocaine seeking is gone,” said Dr. Antonello Bonci, scientific director of the intramural research program at the National Institutes of Health’s National Institute on Drug Abuse (NIDA), where the work was done in collaboration with scientists from the Ernest Gallo Clinic and Research Center at the University of California, San Francisco. What makes the work so promising, Bonci said, is that the investigators are working with an animal model that mimics this sort of compulsive cocaine addiction. The animals, like humans, are more likely to make bad decisions and take cocaine even when they are conditioned to expect self-harm associated with it. Electrophysiological studies showed that the rats had extremely low activity in the prefrontal cortex – the brain region for impulse control, decision making and behavioral flexibility. Similar studies on humans showed the same low-activity pattern in this region in people who are compulsively addicted to cocaine. To test whether altering the activity in this region could impact addiction, the investigators inserted light-sensitive proteins called rhodopsins into neurons in a rat’s prefrontal cortex and activated the region with a laser, turning the nerve cells on and off. The compulsive behavior was wiped out when the cells were activated; deactivating the cells turned nonaddicted rats into addicted ones, the researchers discovered. A similar activation in a human’s prelimbic cortex is possible using a technique called transcranial magnetic stimulation (TMS), which applies an external electromagnetic field to the brain, said Billy Chen of NIDA, the lead author of the study. The method – which places stimulation outside the scalp, rather than zapping the brain with a laser – has been used to treat symptoms of depression. Trials are being designed to test the TMS technique a few sessions a week in people who are addicted to cocaine to see whether activity can be restored to that part of the brain to help them avoid taking the drug. The work, funded by NIDA, was published in Nature (doi: 10.1038/nature12024).