Scientists Discover the Reason behind Infantile Amnesia

Rebecca Lewis May 28, 2013

Neurogenesis or the production of neurons, which is at its peak during the first years of life, is the reason why most of us rarely recall our childhood memories, Canadian scientists report.

Their findings, which were presented at the Canadian Association of Neuroscience, suggest that the formation of new brain cells plays a key role in enhancing cognitive functions. However, it also clears the mind of old memories. According to the study, neurogenesis, which takes place in the hippocampus (the part of the brain responsible for learning and remembering) reaches its peak before and after birth, then declines steadily during childhood all through adulthood.

Researchers from the Hospital for Sick Children in Toronto and the University of Toronto wanted to know how the over-production of neurons affects memory formation. In an experiment on adult mice, they found that the increasing neurogenesis stimulates forgetfulness. In infant mice, the declining rate of neuron production was linked to strengthened memories. This mechanism, according to the researchers, provides explanation for the absence of long-term memories in childhood, also called ‘infantile amnesia’.

"Why infantile amnesia exists has long been a mystery.” said Dr Paul Frankland, senior scientist in neuroscience and mental health at the Toronto Hospital. "We think our new studies begin to explain why we have no memories from our earliest years.”

Dr Frankland explained that at the age of four or five, the brain has a highly dynamic hippocampus which can’t steadily store information, making the recall of memories very difficult.

"This is a very interesting and elegantly executed study which shows a direct link between neurogenesis and memory formation.” said Dr Bettina Forster from the cognitive neuroscience research unit at City University in London. She said the current study puts to test some psychological theories, particularly the link between verbal development and infantile amnesia.

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Neuron growth in children ’leaves no room for memories’