How the Brain Responds to Viewing Human Faces

Researchers analyzed the brains of neurosurgical patients

A group of US researchers was recently able to discover a new type of response to human faces that forms in the human brain when individuals see other people's face. This response was not analyzed before, and researchers say that these results may lead to a better understanding of the brain.

Analyzing the way the brain lights up when it perceives a face is very important towards understanding why we are able to recognize friends from foes at a single glance. We also have the ability to tell who is sad and who is happy, which is also no mean feat.

Neuroscientists at the California Institute of Technology (Caltech), the Huntington Memorial Hospital and the Cedars-Sinai Medical Center, in Los Angeles, were interested in precisely these aspects when they decided to investigate them in detail.

Details of their investigation appear in the latest issue of the esteemed scientific journal Current Biology. Its main conclusion is that a certain type of neurons in the brain becomes highly active when perceiving a full face, but only slightly so when they see only a portion of the same face.

This amazing neuron population is located in the amygdala, a portion of the brain that has been known to code for emotions. It also plays a role in controlling our fears, as well as the body's innate fight-or-flight response.

“The finding really surprised us. Here you have neurons that respond well to seeing pictures of whole faces, but when you show them only parts of faces, they actually respond less and less the more of the face you show. That just seems counterintuitive,” Ueli Rutishauser explains.

The research scientist was a Caltech postdoctoral fellow, and is now visiting the Institute's Division of Biology. He is also the first author of the new paper. The expert says that the study supports the idea that the amygdala is more complex than thought.

A growing body of evidence is showing that this region of the brain is heavily involved in processing and learning a wide variety of social cues, such as hand gestures and faces. What is new in this study are the evidences brought to show that amygdala neurons are selective to full faces only.

“Our interpretation of this initially puzzling effect is that the brain cares about representing the entire face, and needs to be highly sensitive to anything wrong with the face, like a part missing,” Caltech Bren professor of psychology and neuroscience and biology Ralph Adolphs adds.

“This is probably an important mechanism to ensure that we do not mistake one person for another and to help us keep track of many individuals,” concludes the expert, who was also the senior author on the new study.

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