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What if it were possible to stop anyone from overeating, from injecting heroine, or from drinking too much? Researchers from Stanford University say that a preventative treatment for impulsive, destructive behaviors like these might soon be a reality.
In their study published Dec. 18 in the Proceedings of the National Academies of Sciences, Casey Halpern, senior author and assistant professor of neurosurgery at Stanford, and his team discovered an electrical signal — a “moment of weakness” — that occurs in the brain just before a surge of impulsive behavior. They observed the brain signal in mice just before they indulged in high-calorie food pellets and found that delivering a small electrical pulse directly to the nucleus accumbens, the brain’s reward center, prevented the mice from eating the fatty food.
Impulsive behavior is an often-necessary act of survival — turning our feelings about obtaining a reward into tangible action like eating food, having sex, or getting enough sleep. However, in many situations, our impulses can lead to unhealthy, harmful decisions like over-indulging in food or using addictive substances.
Halpern points to the recent allegations of sexual predation on the part of men in powerful positions as one example, where a fundamentally healthy behavior like sex drive has been taken to a compulsive level. “Anything that is extremely rewarding has a risk of provoking abuse,” Halpern told Seeker. “This includes sex, as well as alcohol, drugs of abuse, food, gambling, etc.”
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Halpern thinks the solution to combatting this behavior may be a device implanted in the brain. Currently, deep-brain stimulation (DBS) devices, which deliver electrical pulses to the brain, are approved by the Food and Drug Administration to treat Parkinson’s disease and are in clinical trials to treat depression and obsessive-compulsive disorder. But the timing and duration of these electrical pulses cannot be controlled; they’re delivered on a consistent basis, 24 hours a day.
A new form of intracranial device recently approved by the FDA to treat brain disorders, like partial-onset epilepsy, might serve as a better option for treating impulsive behavior, Halpern believes. The mechanism, known as a responsive neurostimulation device, would monitor the brain’s reward center for signs of the electrical signal that occurs right before an impulsive decision is made and deliver a dose of electricity to suppress the impulse.
“For epilepsy, stimulation is delivered … only when a seizure is detected,” Halpern said. “This ability to only intervene during an ‘at risk moment’ is novel and also appropriate for impulse control.” Because the device can respond to signals in the brain and deliver an electrical pulse only when necessary, it delivers fewer pulses than the DBS device, reducing the risk of side effects.
In their trials with mice, the researchers gave each mouse special high-fat food pellets for one hour every day, for 10 consecutive days. By day 10, the mice became very used to the fatty food and ate it nonstop until it was taken away. Electrode arrays, to detect and administer electrical current, were implanted in the brains of the mice and researchers observed heightened electrical activity emerge right before the mice began binge eating, peaking the second prior to taking a bite. This electrical activity did not happen before the mice ate standard lab food.
Halpern and his team programed the electrode arrays to send 10-second pulses of electrical current to the brain’s reward center, the nucleus accubmens, whenever the electrical activity increased in the mice’s brains. The pulses stopped the mice from binging on the fatty food but did not affect their social activity or any other behavior.
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The team also ran tests on a human participants with obsessive-compulsive disorder, who had been resistant to all prior OCD treatments. The patient had recently opted for surgical implantation of a DBS device. While the researchers did not test a responsive neurostimulation device on him, they aimed to detect that same electrical signal observed in mice, in the patient’s nucleus accubmens just before engaging in impulsive behavior.
The patient was asked to perform several computerized tasks that when completed successfully, rewarded him with cash prizes. As the team hypothesized, when the patient was close to receiving the reward, a receiver detected this electrical pulse, or biomarker, in his brain.
“We only looked at this brief moment in time, that is the 4 second period when the participant was anticipating a loss or gain of smaller or larger sums of money,” Halpern said. “We detected this biomarker only before larger sums of money were anticipated.”
Very similar signals emerged in both the mice and the human participant, prior to two different reward-centric behaviors, leading Halpern to conclude that this signal is likely associated with varied impulsive behaviors. This means potentially all impulsive behaviors could be treated by delivering electricity through a responsive neurostimulation device, though Halpern cautions that clinical studies to test the device on more than one human participant are needed.
Still, Halpern is confident that responsive neurostimulation has the potential to help treat conditions like obesity, substance abuse, or sex addiction, when all other available methods of treatment have failed. “We are interested in all possibilities,” Halpern said. “We are very interested in the opiate crisis, obesity, and all kinds of neuropsychiatric disorders that are resistant to current treatment options.”
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