Memories and aging have a complicated relationship. It’s sad to think that the majority of humans spend a lifetime creating memories, only to lose them at an elderly age. What’s even more interesting is that some people remain mentally sharp for the entirety of their long lives.

A study from researchers at Harvard Medical School have identified a mechanism that helps neurons to sharpen new memories. Researchers looked at the brain’s hippocampus, which is the only area of the organ that continues to generate neurons after birth, to understand how new and old memories are stored.

"The hippocampus allows us to form new memories of 'what, when and where' that help us navigate our lives," said the study's corresponding author, Amar Sahay, PhD, "and neurogenesis — the generation of new neurons from stem cells — is critical for keeping similar memories separate."

Basically, as the human brain ages there is a decrease in neurogenesis, and that decline in neurons makes it more difficult to retrieve and sort memories. With old age, the brain also strengthens its connections with mature neurons, which are responsible for encoding older memories. Meanwhile, young neurons carry newer memories.

Inside the hippocampus, young neurons must compete with mature neurons to survive in the brain and integrate into its memory circuit.

The researchers studied the brains and memories of mice. The team examined their minds after increasing the number of new neurons being integrated into the hippocampus. In the new study, mice with increased neurogenesis in middle age and aging exhibited better memory precision.

"We believe that by increasing the hippocampus' ability to do what it's supposed to do and not retrieve past experiences when it shouldn't can help," said Sahay — supporting the theory that these results may be particularly useful for individuals suffering from post-traumatic stress disorder, mild cognitive impairment, or age-related memory loss.

Source: Sahay A. Making Memories Stronger And More Precise During Aging. Neuron. 2016.

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