While vision is continuous, people move their eyes from point to point three to four times per second. In this study, the investigators found that when the eye touches the face, certain cells in the amygdala, the part of the brain that processes social information, responds and activates generating activity. memory.
“You could easily argue that the face is one of the most important objects we look at” Ueli Rutishauser, PhD, director of the Center for Neuroscience and Medicine at Cedars-Sinai and senior author of the study. “We make many important decisions based on looking at faces, including whether we trust someone, whether the other person is happy or angry, or whether we’ve seen the other person. this before or not.”
To conduct their experiments, the investigators worked with 13 epilepsy patients who had electrodes implanted in their brains to help determine the focus of their seizures. The electrodes also allow the researchers to record the activity of individual neurons in the patient’s brain. While doing so, the researchers tracked the position of the subject’s eyes with a camera to determine where they were looking on the screen.
The researchers also recorded the theta wave activity of the study participants. Theta waves, a distinct type of brain electrical wave, are generated in the hippocampus and are key to information processing and memory formation.
First, the investigators showed study participants images that included human and primate faces and other objects, such as flowers, cars, and geometric shapes. Next, they showed the participants a series of pictures of human faces, some of which they had seen in the first activity, and asked if they remembered them.
The investigators found that every time the participants’ eyes prepared to focus on a human face – and not any other type of image – certain cells in the amygdala set off fire. And every time these “face cells” activate, the pattern of theta waves in the hippocampus reset or restart.
“We think this is a reflection of the amygdala preparing the hippocampus to take in new socially relevant information that will be important to keep in mind.” Rutishauser, Chair of the Board of Governors for Neuroscience and professor of Neurosurgery and Biomedical Sciences.
“Studies in primates have shown that theta waves restart or reset every time they move their eyes” Juri Minxha, PhD, a postdoctoral scholar in neurosurgery at Cedars-Sinai and first co-author of the study. “In this study, we show that this also happens in humans, and it’s especially strong when we’re looking at other people’s faces.”
More importantly, the researchers showed that the faster the subjects’ facial cells fired when their eyes were fixed on a face, the more likely the subject was to remember that face. As the subject’s face cells fire more slowly, the face they have fixed may be forgotten.
The subjects’ facial cells also acted more slowly when they were shown faces they had seen before, indicating that those faces were already stored in memory and that the hippocampus did not need to be remind.
These results suggest that people trying to remember faces may have amygdala dysfunction, Rutishauser said, noting that this type of dysfunction is linked to disorders related to social cognition. , such as autism.
The results also point to the importance of both eye movements and theta waves in the memory process, Rutishauser said.
“If theta waves in the brain are missing, this process that is activated by the amygdala in response to faces may not take place.” Rutishauser said. “Therefore, restoring theta waves could prove to be an effective therapeutic target.”