Healthcare (Commonwealth Union) – Although we absorb a vast amount of knowledge in our early years, we are unable to recall specific moments from that time once we reach adulthood. Scientists have long theorized that this occurs because the hippocampus—the brain region responsible for storing memories—continues to develop throughout adolescence and is initially incapable of properly encoding experiences. However, new research from Yale challenges this assumption.
In a recent study, Yale researchers introduced infants to new images and later assessed their ability to recognize them. The results showed that infants whose hippocampus was more active when first seeing an image were more likely to exhibit signs of recognition later.
Published on March 20 in Science, these findings suggest that memories can, in fact, be formed in the earliest stages of life. Researchers are now exploring what becomes of these early memories as time passes.
The inability to recall events from infancy is known as “infantile amnesia,” but investigating this phenomenon presents significant challenges.
According to Nick Turk-Browne, a psychology professor at Yale University‘s Faculty of Arts and Sciences, director of Yale’s Wu Tsai Institute, and a senior author of the study, the defining characteristic of episodic memories is the ability to share them with others. However, this is not possible when working with infants who cannot yet speak.
To examine infants’ episodic memory, the researchers sought a reliable testing method. Led by Tristan Yates—who was a graduate student at the time and is now a postdoctoral researcher at Columbia University—the team designed an experiment involving infants between four months and two years old. The infants were first shown an image of a new face, object, or scene. Later, after viewing several other images, they were presented with a side-by-side comparison of a previously seen image and a completely new one.
“When babies have seen something just once before, we expect them to look at it more when they see it again,” said Turk-Browne. “So in this task, if an infant stares at the previously seen image more than the new one next to it, that can be interpreted as the baby recognizing it as familiar.”
In a recent study, researchers who have spent the past decade refining techniques for conducting functional magnetic resonance imaging (fMRI) on awake infants—an achievement given the challenges posed by their short attention spans and difficulty remaining still—examined activity in the hippocampus as the infants viewed images.
The study specifically investigated whether hippocampal activity correlated with the strength of an infant’s memory. The results revealed that the more active the hippocampus was when an infant saw a new image, the longer they focused on it when it appeared again later. Notably, the strongest encoding activity occurred in the posterior hippocampus (the region closer to the back of the head), which is the same area most closely linked to episodic memory in adults.
These patterns were observed across all 26 infants in the study, but they were most pronounced in those older than 12 months, who made up half of the sample group. This age-related difference is helping refine theories on how the hippocampus develops to facilitate learning and memory, explained Turk-Browne.
Previous research by the team found that even at just three months old, infants’ hippocampi engaged in a different type of memory known as “statistical learning.” While episodic memory involves recalling specific events—such as having dinner with out-of-town guests—statistical learning enables infants to detect patterns across experiences, such as recognizing the common features of restaurants, identifying which cuisines are prevalent in certain areas, or understanding the typical sequence of being seated and served.
These two memory processes rely on distinct neural pathways in the hippocampus. Prior studies on animals have shown that the pathway supporting statistical learning, located in the anterior hippocampus (the region closer to the front of the head), matures earlier than the one associated with episodic memory.
