Addiction and the problem of relapse
Research on the brain is showing that addiction is a matter of memories, and recovery is a slow and hesitant process in which the influence of those memories is diminished.
Studies have shown that the initial target of addictive drugs is a circuit in the middle of the brain centering on a region called the nucleus accumbens. It is sometimes called a reward circuit because if it is functioning properly, it provides pleasure or satisfaction when we experience something that is directly or indirectly useful for survival or reproduction.
The reward circuit provides incentives for action by registering important events and experiences and their adaptive value. Rewarding experiences cause the release of the neurotransmitter dopamine, telling the brain: "Do it again." The brain records what "it" is through connections to centers of memory and emotion in the amygdala and hippocampus. Control centers in the frontal cortex use this information to judge the value of the reward, compare it with other rewards, and make plans. Dopamine activity increases not only when the brain is obtaining a reward but when it anticipates one.