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October 22, 2007
Brain imaging shows similarities and differences in chimps and humans

By lisa newbern

In the first study of its kind, researchers at the Yerkes National Primate Research Center used functional brain imaging to assess resting-state brain activity in chimpanzees to compare chimp brain activity to that of humans.

The researchers’ findings, which appear in the current Early Edition of the Proceedings of the National Academy of Sciences, suggest that chimps may engage in thought processes similar to those of humans at rest, as well as thought processes that are quite different. The findings are significant because they show the uniqueness of humans, as well as our similarity to our closest living primate relative.

According to lead researcher Jim Rilling, “Examples of resting-state thoughts are when your mind wanders to past social interactions, to potential future social interactions and to problems you need to solve.”

Working with his research team — Sarah Barks, Todd Preuss and Lisa Parr — and using positron emission tomography, Rilling studied eight humans and five chimps. Results showed significant overlap in brain activity patterns such as high levels of activity in the medial prefrontal and medial parietal cortex, brain regions associated with reflecting on mental states of self and others. Results also showed differences with humans, including activity in regions associated with language and the analysis of meaning; these were found in humans but not chimps.

The researchers reasoned if the pattern of brain activity in chimps at rest is similar to humans, there is likely to be some similarity in cognition; conversely, they thought, if there are differences in brain activity during rest, it would imply differences in resting-state cognition.

“This study bears on important issues in comparative psychology, specifically whether chimpanzees understand that other beings have minds. This study doesn’t resolve the issue, but it does suggest humans and chimpanzees share brain systems involved in thinking about one’s own behavior and that of others,” Preuss said.

Researchers plan to further study chimp brain activity by imaging the animals while they are engaged in tasks that specifically drive mental processes the researchers hypothesize to be ongoing at rest.

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