A team of researchers at Ohio State University pinpointed the area of the brain that recognizes human facial expression. Their recent study reveals that this region - the posterior superior temporal sulcus (pSTS) - is on the right side of the brain behind the ear.
The study utilized functional magnetic resonance imaging (fMRI) to identify the pSTS as the region that is activated when their test subjects viewed images of people making various kinds of facial expressions. Using the subjects' fMRI images and comparing them to facial muscle movements in test photographs, the team created a map of pSTS regions that activate for specific facial muscle groups
In addition, the study revealed that particular neural patterns within the pSTS are used for specific facial movements, such as a furrowed brow.
"That suggests that our brains decode facial expressions by adding up sets of key muscle movements in the face of the person we are looking at," said Aleix Martinez, a professor of electrical and computer engineering at Ohio State and senior author of the study.
Martinez and his team used a machine learning algorithm to pinpoint the unique brain activity linked to specific facial expressions using just an fMRI signal.
"Humans use a very large number of facial expressions to convey emotion, other non-verbal communication signals and language," Martinez said. "Yet, when we see someone make a face, we recognize it instantly, seemingly without conscious awareness. In computational terms, a facial expression can encode information, and we've long wondered how the brain is able to decode this information so efficiently. Now we know that there is a small part of the brain devoted to this task."
The team's machine learning algorithm has a 60 percent success rate in decoding human facial expressions from fMRI data, no matter which expression is being examined or who is viewing it.
"That's a very powerful development, because it suggests that the coding of facial expressions is very similar in your brain and my brain and most everyone else's brain," Martinez said.
"This work could have a variety of applications, helping us not only understand how the brain processes facial expressions, but ultimately how this process may differ in people with autism, for example," said Julie Golomb, assistant professor of psychology at Ohio State and co-author of the study.
The findings were published in the April 20 issue of The Journal of Neuroscience.
