Where does our tendency to pet furry animals or scream at the sight of spiders come from? New research suggests that the right amygdala in our brains responds preferentially to the presence of animals.
Located deep inside the brain's medial temporal lobe, the amygdalae are a pair of neuron clusters associated with processing emotional reactions.
An international team of researchers examined the brain activity of 41 epilepsy patients, who already had electrodes placed in different brain regions to monitor seizures.
The study participants were shown images of people, animals, landmarks, and other objects whilst neuron-by-neuron responses were monitored via the electrodes.
"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," said Florian Mormann, study lead author and a California Institute of Technology (Caltech) alumnus, in a press release.
"This preference extends to cute as well as ugly or dangerous animals and appears to be independent of the emotional contents of the pictures," he noted.
"Remarkably, we find this response behavior only in the right and not in the left amygdala."
Previous research has shown that the amygdala is important for processing emotional reactions, but this new study shows a distinct hemispheric asymmetry in the amygdala for responding to animals.
Co-author Ralph Adolphs at Caltech said this is a novel finding because until now most amygdala research has been about fear responses to human faces.
"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," said Adolphs in the release.
"I think this will stimulate more research and has the potential to help us better understand phobias of animals."
The study was published in the journal Nature Neuroscience on Aug. 28.