Annabell Timset: Why the brain hangs on to some memories but lets others fade

Leo Chenyang Lin was on a trip to New Hampshire two years ago when he stopped to watch a group of squirrels darting through the trees. That “playful moment” stuck with him. By the end of that day, he realized he could recall that moment “in vivid detail” — and also the farm animals he and his colleagues had passed earlier, on their way to their destination.

These were scenes that Lin, a doctoral student in the Reinhart Neuroscience Lab at Boston University, believes he wouldn’t normally have remembered. He said the experience made him wonder: Why does the human brain hold on to some seemingly ordinary moments while letting others slip away?

That question is at the heart of a study published Wednesday in Science Advances that researchers hope will have broad practical implications — for example, in the way teachers seek to maximize information retention in their students, or how caregivers interact with people with dementia.

Written by Lin and other researchers at Boston University, the study finds that our brains selectively strengthen certain memories when they are associated with important experiences, in a mechanism known as memory enhancement. As part of that process, the brain uses a sliding scale to decide which memories to preserve, according to the study, which relies on the findings of 10 individual studies involving close to 650 participants.

The study, which has been peer-reviewed, suggests that tying “fragile” memories — of typically routine events — to memorable or rewarding moments could prevent them from slipping away, and that doing this in a systematic way could help strengthen useful memories or weaken irrelevant ones.

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