Small region of brain recognizes facial expressions

Raised eyebrows? Wrinkled nose? Curled up corners of the lips? Most people looking at such expressions would immediately recognize surprise, disgust or happiness. Scientists have known for some time that people tune in to specific facial movements as they read another person’s emotions. Now researchers at Ohio State University in Columbus have identified which part of the brain accomplishes this feat.

Aleix Martinez led the study. As a computational biologist, he uses computer programs to better understand living things. Identifying which part of the brain interprets facial expressions is a challenge, however. Researchers can scan the brain to find the parts that are active when this is happening, Martinez notes. But scans give only a broad view of brain activity. He likens it to “looking at what people do from a satellite image.” So his team developed computer programs that could identify key complex patterns of brain activity.

The group began by selecting photos of people making different facial expressions. The scientists chose 144 pictures of each of seven emotions. They were disgust, happily surprised, happily disgusted, angrily surprised, fearfully surprised, sadly fearful or fearfully disgusted. Each expression uses specific muscle movements. One might raise the inner or outer eyebrows. Another might pull on the corners of the lips. Still another might stretch the lips horizontally.

The team recruited 10 college students to look at these images. While the students viewed them, the researchers scanned their brains. They used a magnetic resonance imaging, or MRI, machine. These tools use a powerful magnet to monitor blood flow in the brain. The resulting images highlight which areas of the brain were active during the scan.

MRI scans while some outside event (such as listening or reading) takes place is called functional magnetic resonance imaging, or fMRI. This technique allows researchers to see which areas of the brain become active during such a task. For this study, the students looked at photos while inside the MRI scanner.

They viewed the faces in 168 blocks of six. During a block, each photo appeared for 1.5 seconds. After a blank half-second, the next image appeared. All photos in a block showed the same type of expression. But each expression was made by a different person. At the end of the block of photos, the college students chose the emotion they had just seen.

One particular brain region went to work when each person viewed the photos. It is known as the posterior superior temporal sulcus (pSTS). This region sits behind each ear. But only the pSTS on the right side lit up. Martinez and his team then used brain-scan data from nine of the students to train their computer program. The program learned to recognize what happened in that brain region when specific parts of the face moved in certain ways.

The team then tested the program. They asked it to identify which facial expression the tenth student had viewed. The program could base its conclusions only on which part of the brain had been active. The researchers repeated this 10 times. Each time they used a different student’s data to test the program. Six of 10 times the program correctly identified which facial expression a student had viewed.

Martinez and his team described the findings April 20 in the Journal of Neuroscience.

“This research helps us understand an important intermediate step in this visual process,” Martinez says. Our brains must first process basic information on what has been seen, he notes. That includes things like lines and edges. The pSTS region of the brain helps turn that basic information into an understanding of faces, emotions and social cues.

The brain region they identified is the same one that helps us recognize when people and animals move, notes Madeline Harms. This psychologist at the University of Wisconsin in Madison was not involved with the study. The researchers used a new technique to align the brain scans of different people, she notes. “It will be exciting to see this technique applied to autism and other disorders in which emotion recognition is a problem.”

Power Words

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autism   (also known as autism spectrum disorders) A set of developmental disorders that interfere with how certain parts of the brain develop. Affected regions of the brain control how people behave, interact and communicate with others and the world around them. Autism disorders can range from very mild to very severe. And even a fairly mild form can limit an individual’s ability to interact socially or communicate effectively.

brain scan    The use of an imaging technology, typically using X rays or a magnetic resonance imaging (or MRI) machine, to view structures inside the brain. With MRI technology — especially the type known as functional MRI (or fMRI) — the activity of different brain regions can be viewed during an event, such as viewing pictures, computing sums or listening to music.

computational biology   A field in which scientists use mathematics and computer programs to better understand living things.

fMRI (functional magnetic resonance imaging)   A special type of machine used to study brain activity. It uses a strong magnetic field to monitor blood flow in the brain. Tracking the movement of blood can tell researchers which brain regions are active. (See also, MRI or magnetic resonance imaging)

magnetic resonance imaging (MRI)    An imaging technique to visualize soft, internal organs, like the brain, muscles, heart and cancerous tumors. MRI uses strong magnetic fields to record the activity of individual atoms. 

neuroscience    Science that deals with the structure or function of the brain and other parts of the nervous system. Researchers in this field are known as neuroscientists.

posterior superior temporal sulcus (pSTS)    A region of the brain located behind the ear that is involved with processing movement in other people and animals.

psychology    The study of the human mind, especially in relation to actions and behavior. To do this, some perform research using animals. Scientists and mental-health professionals who work in this field are known as psychologists.

social    (adj.) Relating to gatherings of people; a term for animals (or people) that prefer to exist in groups. (noun) A gathering of people, for instance those who belong to a club or other organization, for the purpose of enjoying each other’s company.