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Why do we make certain decisions? For example, are you motivated to study for a class at the beginning of the semester when the first exam is over a month away? Would you baby-sit on a Saturday night? If you had to give up a party, but would be paid double, would you consider missing your party? What encourages you to get involved in volunteer work?
There are circuits of nerve cells in the brains of humans and other animals that act as a reward system. They create pleasurable feelings when we engage in adaptive behaviors, making us want to repeat the task. Unfortunately, by inappropriately activating these neural circuits, drugs can hijack them. Activation of the reward system has a very powerful impact on behavior. For example, if a rat receives stimulation to the reward center in its brain when it presses a lever, it will continue to press the lever, actually ignoring food and eventually starving to death.
Why This Science Matters
According to the 2004 National Survey on Drug Use and Health, an estimated 22.5 million people had abused drugs or alcohol during the previous year. Substance abuse costs taxpayers hundreds of billions of dollars each year, due to lost productivity, health care, auto accidents, crime and extra law enforcement.
By knowing how the brain responds to addictive drugs, we can better understand addicts' behaviors and the choices they make, which is the first step toward developing better treatment programs, or, even better, preventing people from becoming addicted in the first place. This lesson and the lecture video with Professor Terrence Sejnowski, explore our current state of understanding about the brain's reward system and how drugs affect it.
Lesson developed by Juanita Quevedo, who teaches chemistry at the School of Science and Technology at San Diego High School.