A scan of an injured brain often produces a map of unrecoverable loss, which reveals points where damage causes memory difficulties or tremors.
But in rare cases, these scans can expose the opposite: plots of brain regions where an injury miraculously relieves someone’s symptoms, providing clues as to how doctors can achieve the same.
A team of researchers has now taken a fresh look at a set of brain images of this type, taken from nicotine-addicted smokers in which strokes or other injuries helped them spontaneously quit smoking. The results, the scientists said, showed a network of interconnected brain regions that are believed to support addiction-related disorders that can affect tens of millions of Americans.
The study, published Monday in the scientific journal Nature Medicine, supports an idea that has recently gained momentum: that addiction does not live in one region of the brain or another, but in a circuit of regions linked by filiform nerve fibers. .
The results may provide a clearer set of goals for addiction treatments that provide electrical pulses to the brain, new techniques that have proven promising in helping people quit smoking.
“One of the biggest problems with addiction is that we don’t really know where the main brain problem we need to focus on treatment is,” said Dr. Juho Joutsa, one of the study’s lead authors and neurologist. the University. from Turku to Finland. “Hopefully after that we have a very good idea of these regions and networks.”
Research over the past two decades has consolidated the idea that addiction is a brain disease. But many people still believe that addiction is voluntary.
Some independent experts said the latest study was an unusually powerful demonstration of the role of the brain in substance use disorders. Among smokers who had strokes or other brain injuries, those who had damage to a particular neural network experienced immediate relief from their cravings.
The researchers replicated their findings in a separate group of patients with brain injuries who completed an alcoholism risk assessment. The brain network associated with a lower risk of alcohol addiction was similar to that which alleviated nicotine addiction, suggesting that the circuit may be the basis for a broader set of addictions.
“I think this could be one of the most influential publications not only of the year, but of the decade,” said A. Thomas McLellan, professor emeritus of psychiatry at the University of Pennsylvania and former deputy director of the National Office. of Drugs. Control policy, which did not participate in the study. “It breaks so many of the stereotypes that still permeate the field of addiction: that addiction is a bad upbringing, addiction is a weak personality, addiction is a lack of morality.”
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In recent years, a succession of studies had identified particular brain regions where an injury or injury appeared to be associated with addiction relief. But the goals were changing.
“People had not been successful in showing consistency in the areas involved,” said Dr. Hamed Ekhtiari, an addiction treatment expert at the Laureate Institute for Brain Research in Tulsa, Okla.
In the new study, Dr. Joutsa applied sophisticated statistical techniques to an old set of brain scans of smokers in Iowa who had suffered neuronal damage. An earlier analysis of the same scans had suggested that patients with damage to the insula, a brain region involved in conscious impulses, were more likely to quit.
But Dr. Joutsa, going back on the same pixel-by-pixel scans, realized that many uninjured patients on the island had also lost the urge to smoke. “There was something in the history of the island, but it wasn’t the whole story,” he said.
Working with Dr. Michael Fox, an associate professor of neurology at Harvard Medical School, Dr. Joutsa examined a second set of scans of smokers who had suffered strokes in Rochester, NY. In total, they analyzed 129 cases.
The team struggled to find individual brain regions where injuries would reliably help patients quit smoking. Instead, the researchers used standard brain connectivity diagrams that show how the activity of one region correlates with the activity of another.
Suddenly, researchers were able to locate networks of connected brain regions where the lesions caused an instant relief of nicotine cravings and other networks where the lesions did not.
“What we are realizing in many different fields is that our therapeutic goals are not brain regions, as we thought before, but connected brain circuits,” Dr. Fox said. “If you consider how connected your brain is, you can improve your treatment.”
The study did not consider how patients’ domestic life (e.g., how often they were exposed to cigarettes) could have affected their habits. Patients who are considered to have entered into remission of addiction after their injuries generally stopped smoking immediately, reported that they did not feel like smoking and did not start again while following them.
Researchers, however, looked at whether other changes associated with injury, intelligence, or mood, for example, could have helped explain the disappearance of nicotine cravings in some patients. Ultimately, they didn’t seem to make any difference.
External experts said the parts of the brain network identified in the study were familiar to them from previous research. Dr. Martijn Figee, a psychiatrist at the Center for Advanced Circuit Therapeutics in Mount Sinai, Manhattan, is studying how electrical impulses delivered to the brain can treat obsessive compulsive disorder, depression, and addiction. He said addiction in general appeared to be associated with low activity in the cognitive control circuit of the brain and overactivity in reward-related circuits.
By applying electrical stimulation to the surface of patients ’heads or using more invasive methods such as deep brain stimulation, doctors can suppress activity in certain regions, mimicking the effect of an injury, and excite activity in others. The study identified a region, called the medial frontopolar cortex, that appeared to be a good candidate for excitatory stimulation; this region overlapped with the goal of a treatment recently approved by U.S. regulators to help smokers quit.
This treatment uses an electromagnetic coil placed against a patient’s scalp to deliver electrical pulses to the surface of the brain. Other techniques involve implanting electrodes in certain brain regions or permanently deactivating specific brain regions.
“This document is really interesting because it clearly indicates some accessible goals” for treatments, Dr. Figee said.
Although brain stimulation has become more common in treating depression and obsessive compulsive disorder, the use of these therapies for addiction has been slower. The researchers said it would take years to perfect the techniques.
Despite studies showing that electrical or magnetic stimulation can reduce the craving for addictive substances, it is unclear how long these effects last. Some of the most promising goals are in the depths of the brain; getting there may require deep brain stimulation or a specific type of coil that was only recently available, Dr. Figee said.
Knowing where to direct brain stimulation also doesn’t solve the question of how often to use it, scientists said. And the connections are different in people’s brains, which increases the possibility of needing to adapt treatments.
People with addictions have been slower to accept brain stimulation than people with depression or movement disorders, the researchers said, partly reflecting the taboo around thinking about addiction as a brain disorder.
There may also be structural challenges. Judy Luigjes, an assistant professor of psychiatry at the University of Amsterdam Medical Centers, recruited from a group of thousands of patients at addiction treatment centers in the Netherlands for a deep brain stimulation study. In three years, only two patients began the trial.
Dr. Luigjes and colleagues wrote that patients with substance use disorder may have avoided the procedure in part because their motivation to address the disease fluctuated more than in patients with obsessive compulsive disorder.
And the same instability that often accompanies substance use disorders can make it difficult to invest in time-consuming treatments. Only a third of patients with an appointment with the research team brought a family member or friend, Dr. Luigjes found.
Some scientists are working to address these concerns. An addiction team in Mount Sinai, for example, has taken the administration of less invasive brain stimulation to patients at home or in community centers instead of the hospital, lowering barriers to treatment.
But while the brain may be a starting point for dealing with addiction, Dr. Luigjes said it was probably not the most important thing. Other scientists have also argued in recent years that focusing on the model of brain disease addiction has diverted attention and money from research that addresses the social and environmental factors that contribute to addiction.
“We’ve put too much of our hopes, money and energy aside,” he said, referring to the field’s focus on brain stimulation. “I don’t know if it will be paid the way we thought.”