How many of us have any memories of being a toddler? Chances are we don't can't recall any incidents that have occurred before the age of 3 or 4. The so-called "infantile amnesia", scientists believed, was due to our hippocampus - an area of the brain crucial to encoding memory - not having developed completely in those years. Yet, in some mysterious way, our tiny brain figures out and stores social and verbal patterns to form a bond with their parents.
The findings of a new brain imaging study cleared this mystery. All of us would have used hippocampus to recognise and learn patterns. And what's fascinating is, we would have done it as young as three-months-old, the study stated.
"A fundamental mystery about human nature is that we remember almost nothing from birth through early childhood. Yet, we learn so much critical information during that time - our first language, how to walk, objects and foods, and social bonds," said Nick Turk-Browne, a professor of psychology at Yale and senior author of the paper. The paper was published in the journal Current Biology.
The researchers arrived at this conclusion after studying the activities in the hipppocampus of 17 infants within in the age of three months to two years. With a new functional magnetic resonance imaging (fMRI) technology, the infants were shown two images - a structured sequence containing hidden patterns that could be learnt and other other, a random incomprehensible order. After showing these two sets of images several times, the infants' hippocampus responded more strongly to the structured image set than to the random image set.
What might be happening, Turk-Browne said, is that as a baby gains experience in the world, their brain searches for general patterns that help them understand and predict the surrounding environment. "This happens even though the brain is not equipped to permanently store each individual experience about a specific moment in space and time - the hallmark of episodic memory that is also lost in adult amnesia," he said.
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The strategy makes sense because learning general knowledge- such as patterns of sounds that make up the words in a language - may be more important to a baby than remembering specific details, such as a single incident in which a particular word was uttered.
The size of the hippocampus doubles in the first two years of life and eventually develops connections necessary to store episodic memories, Turk-Browne said.
"As these circuit changes occur, we eventually obtain the ability to store memories," he said. "But even if we can't remember infant experiences later on in life, our research shows that they are being recorded nevertheless in a way that allows us to learn from them."