New research has revealed that the part of the brain responsible for processing memories is active in babies as young as three months old, despite not being fully formed yet. Known as the hippocampus, this key brain region typically takes a few years to mature, and this lengthy development process is often cited as an explanation for our inability to remember our early infancy.
The discovery that the hippocampus can in fact encode memories in young babies therefore flies in the face of everything we thought we knew about the infant brain. Writing in the journal Current Biology, the authors of this latest study present a new theory, suggesting that young babies are capable of “statistical learning” but can’t yet form episodic memories.
Statistical learning refers to the ability to recognize, understand and predict patterns that help us make sense of our environment. Episodic memory involves the recall of specific events. Previously, it had been assumed that such a capacity for statistical learning only arises after the development of episodic memory, yet the study authors say their findings contradict this hypothesis.
“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 senior study author Professor Nick Turk-Browne in a statement.
To unravel this mystery, the researchers scanned the brains of 17 babies, aged between three months and two years, while they observed two separate series of images. One of these consisted of random, unconnected pictures, while the other contained images that appeared in a structured sequence, with a clear pattern that could be learned.
Results showed that activity in the hippocampus increased after observing the structured sequence of images in all babies, regardless of how developed their hippocampus was. The researchers concluded that the age and size of the hippocampus have no bearing on the brain’s capacity for statistical learning.
Interestingly, though, they found that the activity elicited by observing these patterned images occurred predominantly in the anterior regions of the hippocampus, which are typically not associated with episodic memory formation. As the brain grows during the first few years of life, the posterior hippocampus expands significantly, and it is this region that is believed to be responsible for episodic memory.
The researchers write in the paper that “statistical learning can occur within the hippocampus itself in a way that bypasses the circuitry for episodic memory. Thus, the hippocampus may support statistical learning in infants, as reported in this study, before it can support episodic memory.”
“As these circuit changes occur, we eventually obtain the ability to store memories,” explains Turk-Browne. “But our research shows that even if we can’t remember infant experiences later on in life, they are being recorded nevertheless in a way that allows us to learn from them."