A brain system involved in everything from addiction to autism appears to have evolved differently in people than in great apes, a team reports Thursday in the journal Science.
The system controls the production of dopamine, a chemical messenger that plays a major role in pleasure and rewards.
"Humans have evolved a dopamine system that is different than the one in chimpanzees," says Nenad Sestan, an author of the study and a professor of neuroscience at Yale.
That could help explain why human behavior is so different from our nearest relatives even though our brains are remarkably similar, he says. It might also shed light on why people are vulnerable to mental disorders such as autism.
...Dopamine is best known for its role in the brain's reward system, which responds to everything from sex and food to addictive drugs. But dopamine also helps regulate emotional responses, memory and movement. And abnormal dopamine levels have been linked to disorders including Parkinson's, schizophrenia and autism.
One tantalizing possibility is that dopamine plays a role in humans' unique ability to pursue rewards that are months or even years away. That idea has been suggested by Robert Sapolsky, a professor of biology and neurology at Stanford University.
Sapolsky cites evidence that in humans, dopamine levels rise dramatically when we anticipate rewards that are uncertain and far in the future, like retirement or even the afterlife. That could explain what motivates people to work for things that have no obvious short-term benefit, he says.
The new study doesn't confirm Sapolsky's hypothesis, Sestan says. But the findings do "lead in that direction."
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