They were cigarette smokers. Then a stroke overcame addiction.

A scan of an injured brain often creates a map of irreversible loss, revealing areas where memory damage or tremors are causing the damage.

But in rare cases, these scans reveal just the opposite: plots of brain regions that miraculously relieve someone’s symptoms of an injury, providing clues as to how doctors can achieve the same thing.

A team of researchers has now taken a fresh look at such a set of brain images taken from nicotine-addicted cigarette smokers, which helped them get out of strokes or other injuries on their own. The results, the scientists said, showed a network of interconnected brain regions that they believe addictive disorders are at the root of the disorders that could affect tens of millions of Americans.

A study published in the journal Nature Medicine on Monday supports an idea that has recently taken hold: that addiction does not live in one region of the brain or another, but in a circuit of regions connected by nerve-shaped fibers.

The results may provide a clearer target for addictive treatments that give electrical pulses to the brain, new techniques that have shown hope to help people quit smoking.

“One of the biggest problems with addiction is that we don’t really know where the main problem we need to focus our treatment with is in the brain,” said Dr. Juho Joutsa, one of the lead authors of the research and a neurologist at Turku University in Finland. “After this, we hope to have a very good idea of ​​these regions and networks.”

Research over the past two decades has strengthened 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 a powerful demonstration of the role of the brain in substance use disorders. Among smokers who suffered strokes or other brain injuries, those with damage to a particular neural network immediately relieved their cravings.

The researchers repeated their findings in a different group of patients with brain injuries who conducted an assessment of the risk of alcoholism. The brain network associated with a lower risk of alcohol dependence was similar to that which alleviated nicotine addiction, suggesting that the circuit may be under a broader set of addictions.

“I think it could be one of the most influential publications of the year, not just a decade-long publication,” said A. Thomas McLellan, an emeritus professor of psychiatry at the University of Pennsylvania and a former deputy director of the National Drug Office. Control Policy, not participating in the study. “It puts an end to so many stereotypes that are still prevalent in the field of addiction: that addiction is a bad parent, that addiction is a weak personality, that addiction lacks morality.”

In recent years, a series of studies have identified certain regions of the brain where an injury or an injury was related to the dependency relief. But the goals kept changing.

“People were not successful in showing consistency in the areas involved,” said Drs. Hamed Ekhtiari, an expert in addiction treatment for the Tulsa (Okla) Award-winning Institute for Brain Research.

In the new study, Dr. Joutsa applied sophisticated statistical techniques to an old set of brain scans of Iowa smokers who suffered from neuronal damage. An earlier study of the same study suggested that patients with damage to the island, the regions of the brain involved in conscious impulses, were more likely to quit smoking.

But Dr. Joutsa, going back in the same pixel-by-pixel scan, noticed that many patients with no insular lesions also lost the urge to burn. “There was something in the Insula story, but it wasn’t the whole story,” he said.

Dr. Michael Fox, Associate Professor of Neurology at Harvard Medical School, Dr. Jouts examined a second set of smokers who suffered strokes in Rochester, NY A total of 129 cases were examined.

The team made an effort to find individual regions of the brain where the lesions reliably helped patients to stop smoking. Instead, the researchers turned to standard diagrams of brain connectivity, which show how one activity in one region relates to the activity in another.

Suddenly, the researchers were able to find networks of connected brain regions where the lesions caused immediate nicotine-opening relief and the lesions did not have other networks.

“Therapeutic goals in different areas but the brain are not regions of the brain, as we once thought, connected to the brain circuit,” Dr. said Fox. “If you consider how your brain connects, you can improve your treatment.”

The study did not look at how patients’ lives, such as the frequency with which they were exposed to cigarettes, could affect their habits. Patients were reported to have entered into a remission of addiction after injuries, which generally stopped smoking immediately, they reported that they did not feel like smoking and were not starting to continue again.

The researchers, however, looked at whether other changes related to the injury (e.g., mental or mood) helped explain the disappearance of nicotine cravings in some patients. After all, they didn’t seem to be making any changes.

External experts said parts of the brain network identified in the study were known from previous research. Dr. Martijn Figee, a psychiatrist at the Mount Sinai Advanced Circuit Therapy Center in Manhattan, examines how electrical impulses sent to the brain can treat obsessive compulsive disorder, depression, and addiction. He said that in general, addiction seemed to be related to the excessive activity of the cognitive control circuit of the brain and the excessive activity of the circuits associated with rewards.

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 some regions by mimicking the effect of an injury and in others stimulating activity. The study identified a region called the medial frontopolar cortex that was a good candidate for stimulating stimulation; it overlapped with the goal of a treatment recently approved by U.S. regulators to help smokers quit this region.

This treatment uses an electromagnetic coil placed on a patient’s skin to deliver electrical pulses to the surface of the brain. Other techniques include implanting electrodes in certain brain regions or permanently deactivating specific brain regions.

“This paper is really interesting because it clearly states some of the available goals for treatments,” Dr. said Fige.

Although brain stimulation has become more common in the treatment of depression and obsessive compulsive disorder, the use of these addiction therapies has been slower. The researchers said it would take years to improve the techniques.

Even studies that show that electrical or magnetic stimulation reduces the craving for the addictive substance, it is not clear how long these effects last. Some of the most promising goals are in the depths of the brain; reaching them may require deep brain stimulation or a specific type of coil that was recently available, Dr. said Fige.

Knowing where to direct brain stimulation also does not solve the question of how often to use it, scientists said. And the connections are different in the brains of different people, increasing the need for treatments to be tailored.

People with addiction have been slower than those with depression or movement disorders in taking brain stimulation, the researchers said, reflecting the taboo about thinking addiction as a brain disorder.

There may also be structural challenges. Judy Luigjes, an assistant professor of psychiatry at the University of Amsterdam Medical Center, recruited from a group of thousands of patients in the Netherlands for the treatment of addiction to study in-depth brain stimulation. At three years, only two patients began the test.

Dr. Luigjes and his colleagues avoided the procedure for patients with substance use disorder, in part because their motivation to fight the disease changed more than in patients with obsessive compulsive disorder.

And the instability associated with substance use disorders can make it difficult to invest in long-term treatments. Only one-third of patients who had an appointment with the research team brought in a relative or friend, Dr. Luigi found it.

Some scientists are working to address these concerns. A group of Sinai mountain addicts, for example, provide less invasive brain stimulation to patients at home or in community centers than at the hospital, reducing treatment barriers.

But while the brain may be the entry point for treating addiction, Dr. Luigjes said it was probably not the most important thing. Other scientists have also argued that brain disease in recent years has focused on the addiction model, which has diverted attention and money from research and environmental factors that lead to addiction.

“We put our expectations and too much money and energy aside,” he said, referring to the area’s focus on brain stimulation. “I don’t know if he’ll pay the way we thought he would.”

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