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article imageWhy can’t you remember life as a baby?

By Tim Sandle     May 16, 2014 in Science
The growth and development of new neurons may explain why adults cannot remember being infants, according to a new study.
Infants’ memories may be wiped clean by the growth of new brain cells, a new study in rodents suggests. The findings offer an explanation for why people cannot recall memories from early childhood.
There have been various theories as to why we cannot remember our early years. Over 100 years ago, Sigmund Freud speculated that humans’ tendency to forget their early years, dubbed infantile amnesia, might have a psychosexual origin. Scientists later thought memories might be rooted in language, thus children typically start making long-term memories around the time they start speaking.
Now a new theory has emerged, based on the hippocampus region of the brain. This is the part of the brain that produces new neurons, which scientists believe help make memories.
This theory came from a study in mice. Researchers found that as mice age, the birthrate of neurons slows down. This drop-off matches up with the rodents’ ability to remember events like scary situations.
For their tests, Science Now reports, the researchers placed adult mice in a chamber noticeably different from their usual homes —stripes on the walls and a vinegary smell — and buzzed the animals with mild foot shocks. The mice learned to fear the room, and even 28 days later would freeze up when put in the chamber.
Infant mice were more forgetful. A day after being shocked, their fear began to fade. The animals’ behavior hinted that making new brain cells might be mucking up memory retention. Next, the researchers boosted neuron production, or neurogenesis, in adult mice.
The researchers then shocked adult mice in the striped room and then let them exercise at will on running wheels for days or weeks. Running naturally seemed to trigger the growth of new brain cells in the hippocampus. And just a few weeks of racing on the wheel helped mice forget their fear of the scary room.
The findings have been published in the journal Science, in a paper titled “Hippocampal neurogenesis regulates forgetting during adulthood and infancy.”
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