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Pleasure and pain
Avoiding Pain

The PET-scan images to the right show the brain’s response to the avalanche of dopamine in the nucleus accumbens of people with dependencies. To relieve the chronic stimulation of its neurons, the nucleus accumbens simply reduces the number of dopamine receptors that they have.

In these images of the brain, the red areas indicate large numbers of dopamine receptors. These images show that people who are alcoholic, obese, or cocaine-dependent have fewer dopamine receptors than normal people do.


The brain regions involved in the sensation of pleasure and reward are among those most affected by drugs.

The nucleus accumbens, together with the ventral tegmental area, constitutes the central link in the reward circuit. The nucleus accumbens is also one of the brain structures that is most closely involved in drug dependency.

The nucleus accumbens provides liaison between the limbic system, which is the seat of the emotions, and the central grey nuclei, which help in planning movements and reasoning processes.


The nucleus accumbens appears to be involved in controlling our motivations. Also, the frequent consumption of a drug is known to tremendously increase the amount of the main neurotransmitter in this part of the brain, dopamine. We can therefore better understand the drug addict’s obsessive drive to keep seeking more of the drug.

But the nucleus accumbens is not isolated from the other brain structures that are also influenced by drugs.

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