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The primary system on which addictive drugs operate is the brain’s gratification network, commonly called the Limbic, or Reward System. This network is an ancient part of the brain, pre-dating the structures involved in memory.¹ Thus, the vast majority of activity there takes place unconsciously.²

The Limbic System is also pre-rational in that it pre-dates the evolution of rational brain networks.³

The key neurotransmitter that stimulates this system is dopamine.⁴ If enough dopamine is released into the brain’s reward circuits euphoria results.

Dopamine-based exhilaration is a common experience, at least partially responsible just about anytime one experiences pleasure. “A hug, a kiss, a word of praise or a winning poker hand”⁵can trigger a dopamine spike. When your team pulls out an improbable victory at the last second — think Joe Montana, Dwight Clark and “The Catch” — the delirium you feel if you’re a 49er fan is the rush of dopamine stimulating the brain’s Limbic system. By contrast, the crushing disappointment felt by Cowboy fans was, at least in part, the result of dopamine depletion.

Researchers discovered that normal dopamine spikes are triggered by the unexpectedness of a reward.⁶ (For more on this subject, click on Dopamine Basics.)

But dopamine and the Limbic System are involved in more than just pleasure. For more, click on Dopamine: Learning, Memory and Motivation.

For the next article in the Brain Overview series click here.

To go back to the Addiction Science Menu click here.

 1. A Depression Switch?; New York Times Magazine, Apr. 2, 2006.

2. Hijacking the Brain Circuits With A Nickel Slot Machine, New York Times,

3. Psychoactive Drug Use in Evolutionary Perspective; Science, Oct. 3, 1997.

4. Hijacking the Brain Circuits With A Nickel Slot Machine, New York Times, February 19, 2002.

5. Addicted, Time Magazine, May 5, 1997.

6. Hijacking the Brain Circuits With A Nickel Slot Machine, New York Times, February 19, 2002.