Cocaine abusers may find it difficult to control their addiction because of a “back door” in their brain that causes them to lose self-control; this neural circuit, unknown until now, has been discovered by scientists at the University of Cambridge. Their study has been done in rats, but the researchers believe their findings will be relevant to humans.
Drugs trigger the release of dopamine in the brain, which is why they cause euphoria. Taking them begins as a voluntary act, but over time it becomes a habit that the individual does not control, something that also happens in rats.
Previous work led by Professor Barry Everitt of the Cambridge Department of Psychology had shown that when these animals were voluntarily allowed access to cocaine , dopamine-related activity took place in an area of the brain known as the nucleus accumbens, which plays an important role in goal-directed behavior: for example, that of rats searching for drugs.
However, when rats were administered cocaine for a long period of time, this activity was transferred to the dorsolateral striatum, key to habits, suggesting that the rats lost control and developed an addictive response.
The brain mechanisms that balance habits with voluntary behaviors involve the prefrontal cortex, the area of the brain that directs our behavior. Chronic exposure to drugs alters the prefrontal cortex, but also an area of the brain called the basolateral amygdala, associated with the link between stimulus and emotion and which stores the pleasant memories linked to cocaine; but the prefrontal cortex manipulates this information and helps the individual decide whether or not to take the drug: if the subject consumes it, the dorsolateral striatum mechanisms are activated and addiction occurs.
However, the study with rats published in the journal Nature Communications by Professor Everitt and Dr. Belin, from the Department of Pharmacology at the University of Cambridge, reveals that there is a brain shortcut that links voluntary impulses with habits. This circuit joins the basolateral amygdala with the dorsolateral striatum and “skips” the passage through the prefrontal cortex. This means that an addict may not be aware of his desire to use the drug.
As Dr. Belin explains, “We have always assumed that addiction is caused by a failure of our self-control, but now we know that this is not always the case. We have found a back door that leads to habits. Drug addiction is often seen as a psychiatric disorder, and many of its treatments work to restore the prefrontal cortex’s ability to control drug use. But our research shows that the prefrontal cortex is not always aware of what is going on, and that these healing methods could be ineffective “.
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