CUCUMBERS AND PICKLES: CHANGES IN THE BRAIN

CUCUMBERS AND PICKLES: CHANGES IN THE BRAIN

So what changes between the fifth time that you get your muffin and the time that you waited at the bakery door until opening time each day, neglecting your job or forgetting to take your children to school? You do this even if the muffin tastes lousy. It is this sort of compulsive, repetitive involvement in drug taking despite negative consequences that most experts view as addiction.

Use of addictive drugs can be viewed in a similar way. Many people drink alcohol occasionally, or even sometimes use cocaine at parties. However, for some people, the first social experiences with drugs gradu­ally evolve into more continual use. Alcohol use provides an example. While 50 percent of the adult population of the United States drink alco­hol occasionally, of these about 10 percent drink heavily and about 5 per­cent engage in addictive patterns of drinking.

Clearly, something happens in addicts that makes the need to consume drugs so great that they will go to extreme lengths to obtain the drug. What changes in the brain explain this? We have heard recovered addicts compare the change in their behavior and lives to the change from a cucumber to a pickle. Once a cucumber is turned into a pickle, it cannot

be turned back. Is this a real analogy? If so, then the Alcoholics Anony‑ mous approach of lifetime abstinence from drugs becomes a convincing solution to alcoholism.

Most scientists think that changes gradually occur in the reward circuit of the brain as it adapts to the continuous presence of the drug. However, we don't completely understand exactly which changes are the most important for addiction. The simplest change is easy to understand: with daily stimulation by addictive drugs, the reward system comes to "expect" this artificial stimulus. When people stop using drugs abruptly, the reward system is shut down—it has adapted to the daily "expectation" of drugs to maintain its function. We know of one biochemical change in the brains of all addicts that may explain this result. The brains of alcoholics, meth-amphetamine addicts, heroin addicts, and even compulsive eaters show a common biochemistry—they have low levels of one of the receptors that normally receive dopamine. This makes sense—in response to a constant barrage of dopamine, the cell that receives it is just trying to shut down. Recovering heroin addicts often report that every time they inject heroin, they are trying to recapture the feeling of their early experience with the drug, which gave a pleasure that they never quite reached again. People who are in a stimulant "binge," taking hits every few hours, can have the same experience. They respond by "chasing the high," taking the drug every hour or so to recapture the first rush. Only when they stop taking the drug for a while does their initial sensitivity return.

Some recovering cocaine addicts say that they do not feel pleasure in any­thing for a while after they stop using cocaine. Imagine how difficult it must be to stop using a drug that gives incredible pleasure, when even things that are usually enjoyable give no pleasure during withdrawal. This inability to feel pleasure may be one of the powerful reasons why people have great diffi­culty giving up cocaine. If there is a substance at an addict's fingertips that can make him feel better immediately, clearly the impulse to take it can

become overwhelming.

Some of the changes in the brain of a person who uses addictive drugs repeatedly are just a result of normal learning in the brain. Let's go back to our bakery one more time. As our imaginary muffin addict approaches the store each day, he remembers the route and looks forward to the smell of newly baked muffins wafting down the street. Pretty soon, the smell of the bakery alone can cause an intense longing for the pastries before he gets there. What happens when our muffin addict decides that the daily search for muffins is taking too long, or when the bakery raises prices so much that he won't pay? If he goes "cold turkey" and quits muffins alto­gether, he had better find another way to go to work, because he will find that the route to the bakery, the smell of the muffins, and many of the experiences associated with going to the bakery will cause an intense longing for a muffin. This type of longing has ruined many a diet, and this type of learning plays an important role in addiction as well. Simply showing a former cocaine user a photograph of a crack pipe will trigger a strong craving for the drug, and recent studies of brain activity show that areas of the brain involved in memory are activated while he looks at these pictures.

There is another kind of "learning" that happens in the brains of addicts that makes it hard for them to stop using drugs. This is the part of the brain that plans for the future. Under normal circumstances, if an animal or person finds a reinforcer, her brain remembers where and how it happened and plans to check back the next time she needs food or sex. This ability to plan for the future is perhaps the most sophisticated thing our brain does. However, in a crack user, what this part of the brain focuses on is finding crack—the repeated stimulation with this one rein­forcer can also "hijack" these planning centers in the same way. So it isn't simply the pleasure the drugs cause that motivates drug use but our abil­ity to remember and plan for future pleasure. This may be one of the most long-lasting changes that happen in the brain.

New research shows that there is a final step in addiction: when taking the drug becomes as automatic as tying your shoes. Scientists have shown that another part of the dopamine system that is important for the transi­tion of this learning to something automatic gradually changes, too, but more slowly. Eventually, hitting the bar to get an injection of drug becomes a habit. This behavior has become an automatic and controlling part of your behavior.