The Addicted Brain

1. The Addicted Brain Insights from Imaging Studies N. Volkow et. Al.

2. The Dopamine System • Dopamine is a neurotransmitter that regulates motivation and drive for everyday activities. • Dopamine activity decreases as drug use persists, requiring an increase in the use of the drug to achieve the same level of dopamine activity in the synapse.

3. Saliency • Definition: “The saliency of an item is its state or quality of standing out relative to neighbouring items” (Wikepedia) • In a nervous system dysregulated by drugs, the drug -which increases synaptic dopamine availability x3-5, gains more saliency than natural reinforcers such as food, sex, exercise, etc.

4. The reinforcement-reward system • Reward system –the nucleus accumbens • Memory and learning system –amygdala and hippocampus • Motivation and drive system -orbital frontal cortex • Control system –pre-frontal cortex, specifically the anterior cingulate cortex.

5. What the different parts of the reinforcement/reward system do: • Reward centre: (old brain) the ‘more’ part of the circuit. Provides a feeling of satisfaction when a need is fulfilled –or a surge of relief when pain is relieved. • Memory/learning centre: (old brain) stores explicit and implicit emotional memories of the satisfaction obtained, the source of the satisfaction and how it was obtained

6. Continued • Motivation/drive circuit – (sits on border of old and new brain) Involved in planning behaviour associated with a predicted reward or punishment. Acts as a “stop” switch once satiation has occurred. • Control System (in new brain) Concerned with error detection and modulation of emotional responses.

7. Non-Addicted Brain Control Reward Drive Memory

8. Dysregulation of the reward-reinforcement system in drug use. • Reward system: The ‘more’ switch becomes overactive, sending strong ‘do it again’ messages to the motivation/drive controller • Memory/learning circuit receives the ‘cue’ that recalls the agent/behaviour associated with pleasure. It activates the reward centre by releasing dopamine in the reward centre area.

9. Continued • Motivation/drive circuit: The circuit’s evaluation of reward and risk changes as the high-intensity signals from the reward and memory circuits override the motivation/drive circuit’s ‘stop’ switch • The function of the control centre most involved in common-sense, moral reasoning, conscious appraisals of self and identity is weakened.

10. Addicted Brain Control Reward Drive Memory

11. Vulnerability to drug-addiction • Environment and heredity: some individuals may be genetically pre-disposed to developing addictions. • Environmental factors influence brain development by determining which genes become expressed. The interaction of heredity and environment early in the individual’s life may create a susceptibility to drug-abuse later in life.

12. Implications for treatment • Use interventions that: • Decrease the rewarding value of drugs • Increase the saliency of natural reinforcers • Increase rewards for non-drug-related behaviours • Enhance cognitive and emotional regulation