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Why is it easier to remember some things but not others?

Kathleen Blanchard's picture
Why do some memories last a lifetime, but we forget other simple things?

Have you ever wondered why it is so easy to remember some things, but other memories quickly slip away? New research may shed some light on how memories are formed during sleep that can last a lifetime, but other information we receive throughout the day is so easily forgotten.

High value memories are easiest

Scientists at Northwestern University, U.S. say we retrieve memories during sleep, but mostly those that have high value.

The researchers explain we remember things more easily when they have high value. An example is making more money. The reason is because we rehearse the memory and then consolidate it during sleep.

For their study, the scientists manipulated sleep to help people retain information that has less value.

Delphine Oudiette, a postdoctoral fellow in the department of psychology at Northwestern and lead author of the study designed an experiment that required people to remember the placement of objects on a computer screen.

Each object was assigned a monetary reward that could be obtained for remembering where it was located.

Ken Paller, professor of psychology at Northwestern and co-author of the study explained in a press release, “In other words, we manipulated the value of the memories -- some were valuable memories and others not so much, just as the things we experience each day vary in the extent to which we'd like to be able to remember them later."

Each object was also accompanied by a sound, like the whistle of a tea kettle. Some of the sounds were played during wakefulness and sleep.

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To help the study group remember low-value items, soft sounds were played when they were awake and when they were sleeping. The result showed memory improved when sounds associated with lesser value items were played during sleep.

Paller, who is the director of the Cognitive Neuroscience Program at Northwestern, suggests the finding shows memories are stored during sleep. Anything we rehearse during sleep is going to be remembered. Conversely, if we don’t rehearse during sleep, a memory will be forgotten.

The study gives insight into how we store memories, yet others are easily forgotten during the day that was previously unknown and poorly understood.

Memory practice during sleep might make perfect

Paller explains memory changes all the time. If we don’t practice and rehearse, we can’t remember – but much of the rehearsal occurs during sleep.

The focus of research has been on when we first form a memory and how we retrieve it later, the study authors explain. The hope is to learn more about how to reactivate memory during the time in-between, Paller said.

Past studies have shown we form memories during sleep. The current study suggest we retain high value information much more easily. There is still much to be learned about memory consolidation. Memory rehearsal during sleep could be the key to a sharper mind.

Northwestern University
April 12, 2013

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