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Have you ever seen a stranger in public whose face seems eerily familiar? Or maybe a fellow student in the hallways, who you swear you’ve seen some time ago? If you answered yes, then don’t worry, you aren’t going insane, your brain just reacts differently when your eyes see a face. In a study spearheaded by Cedars-Sinai Medical Centre, a Los Angeles based hospital famous for housing celebrity patients such as Stan Lee and Frank Sinatra, researchers discovered valuable information on how memory is triggered when looking at a human face versus other objects or images.
While vision feels continuous, people tend to shift their focus between objects or spots in their vision 3 to 4 times every second. If you casually look around your environment right now, you’ll find that even if you keep your eyes moving, a select few random objects will tend to catch your attention as you look around. In this study, it was found that when the eyes focus on a face, certain cells in the amygdala react and instigate memory forming activity.
The amygdala is the region of the brain that is primarily responsible for emotional processes. The name itself comes from the Greek word amygdale, meaning “almond”, due to the structure’s almond-like shape. The amygdala is responsible for regulating emotions and is also a major factor in an individual’s social behavior, as emotions heavily influence cognitive processes such as memory making and attention.
In this experiment, the scientists worked with 13 epileptic patients with electrodes implanted in their brains. Electrodes in the brain are used to help determine where a seizure starts, however, electrodes are also able to measure the activity of individual neurons within the patients’ brains. While measuring the activity of the patients’ neurons, researchers also used a camera to determine where each patient’s eyes were focused on at any given moment. The patients’ theta waves were also recorded throughout the study. Theta waves are brain waves created in the hippocampus that are responsible for processing information and forming memories.
The investigators first showed the participants a series of images, consisting of both human and primate faces, as well as objects such as flowers and cars. Afterwards, they presented a collection of pictures of human faces, a few of which they had already seen in the first collection, and were asked if they could remember any of the faces.
When participants looked at the first set of pictures, it was found that certain cells in the amygdala would fire when the participants looked at a human face. These “face cells”, however, would only be fired if the eyes rested on an image of a human face, and not any of the other images, including the images of a primate face. It was also found that when these cells would fire, the pattern of the theta cells would reset. Scientists believe that this could be caused by the amygdala preparing the hippocampus for socially relevant information, as faces are arguably one of the most important things we look at during social interaction.
In the second set of photos, it was also discovered that if a subject’s face cells were fired more quickly, then the face that they saw would be more likely to be remembered. Conversely, if a subject’s face cells were fired slowly, then the subject would be more prone to forgetting the face they just saw. The participant’s face cells also fired off slower when looking at a face that was already seen before, indicating that the hippocampus does not need prompting as those faces were already stored away in the brain’s memory.
These results suggest that people with problems remembering faces may have a dysfunctional amygdala, and it is noted that dysfunction in the amygdala is already implicated in disorders related to social cognitive ability, such as autism. The results of this experiment also show that theta waves play a large importance in the memory process. Ueli Rutishauser, PhD, director of the Centre for Neural Science and Medicine at Cedars-Sinai and senior author of the study stated that “If theta waves in the brain are deficient, this process triggered by the amygdala in response to faces might not take place, so restoring theta waves could prove to be an effective treatment target.”
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