Lecture Notes: Reward Pathway in the Brain

Introduction

• Focus on a common response of the brain to rewarding stimuli.
• Brain releases neurotransmitter dopamine in response to pleasurable activities (e.g., hugs, praise, eating cake).

The Reward Pathway

• Dopamine: Key neurotransmitter involved in pleasure and reward.
• Ventral Tegmental Area (VTA): Primary production site of dopamine, located in the mid-brain.
• Dopamine release affects various parts of the brain:
  • Amygdala: Involved in emotions.
  • Nucleus Accumbens: Controls motor functions.
  • Prefrontal Cortex: Involved in attention and planning.
  • Hippocampus: Responsible for memory formation.

Mesolimbic Pathway

• Comprised of VTA connections to nucleus accumbens, amygdala, and hippocampus.
• Main component of the brain's reward circuit.

Function of the Reward Circuit

• Dopamine travels through the mesolimbic pathway, causing feelings of euphoria and reward.
• Example: Eating a delicious piece of cake:
  • Amygdala: Registers the pleasure of taste.
  • Hippocampus: Records details of the experience.
  • Nucleus Accumbens: Engages motor functions to continue eating.
  • Prefrontal Cortex: Focuses attention on the pleasurable activity.

Role of Neurotransmitters in Addiction

• Prolonged dopamine activity reduces serotonin, which is linked to satiation.
• This imbalance can lead to compulsive and addictive behaviors.

Biological Basis of Addiction

• Previously thought to be moral weakness, now understood to have physiological components.
• Genetic predispositions can increase risk.
• Environment and choices also play roles.

Evidence from Animal Models

• Rats conditioned to self-administer drugs, showcasing drug-seeking behavior.
• Addicted rats ignore negative consequences.

Conclusion

• Addiction affects rational decision-making.
• Upcoming topic: Tolerance and withdrawal when pleasurable stimuli are removed.