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Many areas of the brain are involved in addiction, and most of them are found in the limbic system. The interesting thing about addiction is that it isn’t simply about dopamine and the pleasurable feeling it provides. Numerous other systems are involved with addiction, including the endocrine system and certain hormones, as well as other neurotransmitters. The major areas of the brain involved in addiction include the ventral tegmental area, substantia nigra, amygdala, anterior cingulate, prefrontal cortex, hippocampus, and nucleus accumbens (also discussed in Chapter 3).

The nucleus accumbens is the major area in the limbic region of the brain; it’s a dense bundle of cells where a very large number of dopamine receptors reside. Dopamine is one of the major excitatory neurotransmitters responsible for pleasure and movement, and along with serotonin and norepinephrine, it has a lot to do with mood, reward, motivation, pleasure, and compulsion. (Neurotransmitters are chemicals that enable nerve cells to communicate with one another.) The nucleus accumbens is the major traffic center for pleasure for most of the things we do, and as mentioned earlier, the brain is wired to make sure that certain behaviors associated with survival and thriving are pleasurable. It makes sense that nature would do this, as it increases our survival potential. Figure 2-1 shows the reward centers of the brain.

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FIGURE 2-1: The reward centers of the brain.

As you read the following sections, keep in mind that addiction involves borrowing those pleasure pathways meant for survival, so in an odd way, addiction is really a natural phenomenon gone awry — much like many medical conditions. It’s also important to note that the human brain and nervous system are always about checks and balances — where excitatory neurotransmitters are held in check by other inhibitory neurotransmitters such as GABA (gamma-aminobutyric acid).