Ever wonder why people who take a placebo sometimes feel better even though they are not receiving any real medication? A group of researchers at the University of Michigan, Ann Arbor finished a new study that tested the nucleus accubens (NAC), a region deep in the brain that is known to play a role in reward expectation.

Researchers told the study participants that they were testing a new pain-killing drug and that they would receive the drug or a placebo. The researchers then gave all participants a injection of salt water solution and had the patients rate the effectiveness of the painkiller.

According to HealthDay, ?The participants rated their expectation of the pain-killing effects of the "drug," as well as the level of pain relief they felt with and without the "drug" from a moderately painful injection of salt solution in their jaw muscle.

For the first experiment, the researchers used positron emission spectroscopy to measure release from the NAC of the neurotransmitter dopamine -- a chemical trigger of the brain's reward response.?

The study found that the higher the participant rated the expected pain relief of the drug, the greater the dopamine release from the NAC. So the patients that anticipated great relief, felt less pain. Also, patients that reported more relief after receiving the ?drug? showed greater NAC activity when they received the placebo before the pain.

The studies authors said, the findings support the theory that the NAC system may need to be activated to allow the placebo effect to occur. This information may be used in the future to develop new therapies for a variety of conditions.

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