More than a century ago, the zoologist Richard Semon coined the term “engram” to designate the physical trace a memory must leave in the brain, like a footprint. Since then, neuroscientists have made progress in their hunt for exactly how our brains form memories. They have learned that specific brain cells activate as we form a memory and reactivate as we remember it, strengthening the connections among the neurons involved. That change ingrains the memory and lets us keep memories we recall more often, while others fade. But the precise physical alterations within our neurons that bring about these changes have been hard to pin down — until now.
In a study published last month, researchers at the Massachusetts Institute of Technology tracked an important part of the memory-making process at the molecular scale in engram cells’ chromosomes. Neuroscientists already knew that memory formation is not instantaneous, and that the act of remembering is crucial to locking a memory into the brain. These researchers have now discovered some of the physical embodiment of that mechanism.
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