There’s a lot to remember from your time as a baby — your first smile, your first steps, your first words. But chances are, you’ve forgotten all of it, a phenomenon called infantile amnesia.
For a long time, infantile amnesia was thought to be tied to an inability to make memories in infancy. But a new study supports the idea that babies do, indeed, encode memories in the first years of their lives, by linking measures of brain activity to measures of memory recall in infants for the first time.
A New Notion of Memory
Though our days as infants are filled with new experiences, we don’t remember those experiences later on in life. Researchers long thought that the hippocampus, the region of the brain that’s in charge of making memories, wasn’t developed enough during infancy to encode specific events as memories. But the results of the new study indicate that isn’t true.
Published in Science, the study involved 26 infants, all aged 4 months to 2 years old. At the start of the study, the infants’ brains were monitored as they were shown a series of images of faces, objects, or scenes. At the end, the infants were shown a previously seen image along with a new image to test their recall.
Using functional magnetic resonance imaging (fMRI) to measure the babies’ brain activity as they looked at the images for the first time, the researchers revealed a link between hippocampal activation and memory recall, represented by the length of time that the infants looked at a previously seen image.
If the infants’ hippocampal activity was higher when they saw an image for the first time, the study revealed, then they tended to look at the image longer when they saw it for a second time, indicating that heightened activity in the hippocampus had resulted in heightened recall.
Revealed through an approach that mitigated the infants’ movements (which have previously posed a problem for fMRI readings), this pattern of hippocampal activity and recall rang true for all 26 infants. That said, the patterns were most apparent among infants 12 months old or older, providing researchers with a clearer picture of hippocampal ability throughout infancy.
Read More: What Happens in Your Brain When You Make Memories?
Making Memories and Testing Them
According to the study authors, measuring memory recall in infants is a tricky task.
“The hallmark of these types of memories, which we call episodic memories, is that you can describe them to others, but that’s off the table when you’re dealing with pre-verbal infants,” said Nick Turk-Browne, a study author and a psychology professor at Yale, according to a press release. So, to measure memory recall, the study authors turned to a pre-verbal metric — the amount of time that the infants stared at a previously seen image.
“When babies have seen something just once before, we expect them to look at it more when they see it again,” Turk-Browne said in the release. “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.”
Read More: Understanding Memory Recall and Storage in the Brain
Missing Memories?
Ultimately, the new research reveals that we make memories earlier than long thought. But if we do, indeed, make memories earlier, why do these memories disappear before we reach adulthood?
The experiences of infancy may be saved as short-term memories but not as long-term memories and thus slip away as infants age into adults. It is also possible that these memories are stored somewhere out of reach in the brain, remaining there throughout adulthood.
If the latter does turn out to be true, it would indicate that infantile amnesia is not an issue of memory making but of memory retrieval, Turke-Browne said in the release. “We’re working to track the durability of hippocampal memories across childhood, and even beginning to entertain the radical, almost sci-fi possibility that they may endure in some form into adulthood, despite being inaccessible.”
Read More: How The Brain Decides Which Memories To Keep And Which To Discard
Article Sources
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Sam Walters is a journalist covering archaeology, paleontology, ecology, and evolution for Discover, along with an assortment of other topics. Before joining the Discover team as an assistant editor in 2022, Sam studied journalism at Northwestern University in Evanston, Illinois.
