LOS ANGELES, Sept. 9 (UPI) -- U.S. researchers say they've discovered that a certain area of the human brain is hard-wired by evolution to rapidly detect and respond to animals.
Scientists from the California Institute of Technology and UCLA say neurons in the amygdala -- an area of the brain responsible for processing emotional reactions -- respond preferentially to images of animals over other objects. There are two amygdala, almond-shaped clusters of neurons, located deep in the brain.
In the study, 41 epilepsy patients at the UCLA Medical Center already being electrically monitored for brain activity related to seizures viewed images of people, animals, landmarks or objects, a Caltech release said Friday.
"Our study shows that neurons in the human amygdala respond preferentially to pictures of animals, meaning that we saw the most amount of activity in cells when the patients looked at cats or snakes versus buildings or people," Florian Mormann, a former postdoctoral scholar at Caltech, said. "This preference extends to cute as well as ugly or dangerous animals and appears to be independent of the emotional contents of the pictures.
"Remarkably, we find this response behavior only in the right and not in the left amygdala," he said.
Researchers say the study supports the theory that early in vertebrate evolution, the right hemisphere of the brain became dominant in dealing with unexpected and biologically relevant stimuli.
"Nobody would have guessed that cells in the amygdala respond more to animals than they do to human faces, and in particular that they respond to all kinds of animals, not just dangerous ones," Caltech researcher Ralph Adolphs said. "I think this will stimulate more research and has the potential to help us better understand phobias of animals."
