Just imagine if you could predict and prevent a burst of binge eating or alcohol intake, a heroin injection, a sudden bout of uncontrolled rage or a suicide attempt. The world would be a better place.
Long journeys start with first steps. In a study published in Proceedings of the National Academy of Sciences, Stanford researchers led by neurosurgeon Casey Halpern, MD, have identified, both in mice and in a human subject, a signature pattern of electrical activity in a small but important deep-brain region called the nucleus accumbens just a second or two before a burst of impulsive behavior.
The nucleus accumbens is the hub of the brain's reward circuitry, which evolution has engineered to reinforce survival-promoting actions by inducing pleasure in anticipation or performance of those actions. The researchers showed in mice that supplying a small electrical jolt to the nucleus accumbens as soon as the electrical signature manifested there stopped the mice from overindulging in fatty food -- without messing up the rest of its natural activity.
"Impulses are normal and absolutely necessary for survival," Halpern said when I interviewed him for our news release on the new study. "They convert our feelings about what's rewarding into concrete action to obtain food, sex, sleep and defenses against rivals or predators."
But in some contexts, impulsive behavior can be pathological, manifesting as a marked tendency to make poor decisions and act on them. One need look no further than the rash of recent reports about sexual predators perched in powerful positions in Hollywood, the media, finance and politics to see blatant examples of a fundamentally healthy drive -- sexual appetite -- taken to a pathological level.
Halpern focuses on deep-brain stimulation, whereby devices deliver electrical pulses to targeted brain regions in which they've been implanted. Tens of thousands of DBS devices are in current use for treating symptoms of Parkinson's disease and essential tremor, and DBS is in clinical trials for depression, obsessive-compulsive disorder, and multiple other disorders of the brain.
But DBS devices in use today are inflexible; they just keep firing away nonstop on a preprogrammed basis. In the new study, the scientists fitted the mice with new-generation DBS devices that can fire or not fire, depending on feedback they get from sensors in the brain region they target -- in this case, the nucleus accumbens. They identified a particular pattern of electrical activity that arose there just as mice were about to plunge into a pile of high-fat food to which they'd become quite fond, to the point of pigging out on it. But whenever the implanted device detected this pre-gluttony signal, it zapped the nucleus accumbens with an electrical pulse equivalent to one from a standard DBS pulse. That snuffed a mouse's high-fat food bingeing -- but not its intake of normal food, social behavior or other physical activity
The study's findings offer the promise, Halpern told me, of an implantable device that monitors the nucleus accumbens for the telltale signal preceding a burst of impulsivity and immediately delivers a measured dose of electricity. This intervention may prevent impulsive and sometimes life-threatening actions by high-risk people for whom all noninvasive therapies have failed.
Halpern is hoping to find out whether this kind of feedback could be helpful for obese patients who've been unable to curb their dietary intake even after bariatric surgery. The findings could also lead to less noninvasive methods of countering substance-abuse disorders, pathological gambling, sexual addiction or intermittent explosive disorder, a psychiatric condition marked by impromptu outbursts of inappropriate ferocity.
Previously: Why become a doctor? Deep brain stimulation hooked this Stanford neurosurgeon, Stanford study points to precisely positioned deep brain stimulation devices for Parkinson's and Stanford conducts first U.S. implantation of deep-brain-stimulation device that monitors, records brain activity
Photo by Julie Missbutterflies