As drug use or addictive activity escalates, the involvement of various brain regions associated with our emotional state also increases. The brain region most often associated with our emotional state is the extended amygdala. Scientists think this brain region plays an important role in addiction because of its association with emotions and stress.
The amygdala affects emotions and memory. We all have both "good" memories and "bad" memories about various events in our lives. What makes a memory "good" as opposed to "bad" are the emotional states that occurred during those events. When the brain forms these memories, it stores the memory of the event along with the emotions that accompanied it. When I smell the sea air, feel the ocean breeze, and hear the seagulls, I have a pleasant memory and emotional experience. This is because these things have been repeatedly associated with relaxing and enjoyable times. The memory of the sea is stored along with a pleasant emotional state. So I can merely think of the sea, without actually being there, and I will experience a pleasant emotional state. Likewise, an addicted person may only need to think about engaging in their addiction and they will experience pleasure. The memory of engaging in the addiction is stored with a pleasant emotional state. Thus, the pleasing memories of engaging with an addiction can lead to repeating those behaviors and a habit forms.
Emotional memory has another role in the development of addiction, called cue anticipation. Cue anticipation refers to environmental cues that can initiate or elevate craving. Cravings often lead to relapse. For this reason, these cues are often called relapse triggers. Therefore, a successful recovery plan will include a strategy for coping with cues (relapse triggers).
These environmental cues (relapse triggers) can be anything that is associated with the addiction. It could be a certain time of day, a place, a person, or an activity. For instance, suppose a man is addicted to pornography use. He usually gets online after his wife goes to bed. The mere act of his wife getting ready to go to bed serves as a cue that prompts powerful cravings. Later, even his own anticipation of his wife going to bed will serve as a powerful cue. The amygdala's role in emotional memory is responsible for these cues taking root. The brain forms an association between pleasant memories of drug use or addictive activities, and the cues. The more a person repeats this cycle, the more it strengthens the emotional memory circuits associated with these cues. Eventually, this leads to a complete pre-occupation with the addiction.
So far, we've been discussing the role of the amygdala and positive emotional memories. The brain may also form an association between unpleasant emotions and a memory (forming a "bad" memory). These negative emotional memories play an important role in withdrawal. The negative emotional memory of anxiety becomes associated with the physical signs of withdrawal. As withdrawal begins, the symptoms trigger an unpleasant emotional memory. This increases the negative experience of withdrawal. Withdrawal avoidance (via returning to the addiction) often becomes the cornerstone of the addiction in the later stages. Thus, in the earlier stages of addiction the pleasurable experience of the drug motivates a repetition of that behavior. In the later stages, relief of withdrawal symptoms (physical and/or emotional discomfort) achieves pleasure. This pleasurable relief from withdrawal symptoms continues to motivate the repetition of that behavior.