Missing infant memories may be result of brain circuit overload

The fishbowl memories of a toddler and the lack of memories adults have of infancy have been a longtime mystery in the scientific community, but the Canadian Association for Neuroscience believes it has found an answer.

A study released Friday by the association suggests that "infantile amnesia" _ a term coined by Sigmund Freud _ is caused by the mass growth of nerve cells in an area of the brain called the hippocampus.

According to the study, the massive onslaught of new experiences in infancy causes a kind of circuit overload in the area of the brain responsible for storing new experiences in the long-term memory.

"Adults have surprisingly few memories of early childhood despite the seemingly exuberant learning capacity of young children," says the report. "Studies have shown that though young children can remember events in the short-term, these memories do not persist."

The study's researchers, Paul Frankland and Sheena Josselyn from the Hospital for Sick Children in Toronto, say that this shuffling of memories could have the positive effect of increasing the capacity for new learning.

Researchers applied their theory to young and old mice by looking at the portion of their brains where memories are stored.

They suppressed the high levels of neurogenesis — the development of new nerve tissue — in young mice and stimulated increased neurogenesis in older mice.

From that work, the researchers said they were able to show a relationship between a reduction in neurogenesis and increased memory, and on the other side of the coin, a decreased memory when neurogenesis is increased.

Young mice have similar issues with their memory as human infants, which prevent them from retaining information.

In the researchers' study, the baby mice navigated a maze and forgot how to get through it days later. After the decrease of new nerve tissue, the baby mice were able to better retain the information in their long-term memory and could make their way through the maze.

Frankland may get the chance to apply this theory with humans because he encounters many children in his work who take drugs with the side-effect of slowing down neurogenesis.