Memory can be mysterious. Certain life events remain clear in our minds no matter how long ago they occurred, while episodes from the prior day may already be fuzzy and difficult to recall.
A study, published Thursday in Science, reveals why this happens. Scientists have found that the brains of humans and other mammals have a system for choosing which life experiences are important enough to be cemented into long-term memory — and which will be allowed to fade away.
Experiments in mice revealed that during waking hours, cells in the brain’s hippocampus spark in a specific pattern called “sharp-wave ripples,” which tag important experiences for movement into long-term memory storage during sleep.
Although the research was performed in mice, certain brain processes have remained almost the same as mammals have evolved, so the findings can tell us a lot about ourselves, said the study’s senior author, Dr. György Buzsáki, Biggs Professor of Neuroscience at NYU Langone Health.
As part of the research, Buzsáki and his colleagues put mice through a maze that had a sugary reward at the end for those that successfully reached it. Meanwhile, the researchers were monitoring the activity of nerve cells through electrodes implanted in the rodent brains that fed data into computer programs.
They observed that as the mice paused to eat their treats, their brains sparked sharp-wave ripples that were repeated as many as 20 times. The daytime pattern of sharp-wave ripples was replayed during the night, a process that moved the experience into long-term memory.
It’s during sleep when experiences from waking hours deemed to be important are converted into enduring memories.
Events that were followed by very few or no sharp-wave ripples failed to form lasting memories, the researchers noted.
This tagging process during waking hours is totally unconscious, Buzsáki said. “The brain decides on its own, rather than us deciding voluntarily,” he added.
Relaxation…
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