Sleep cherry-picks memories

Boost cleverness:

Charles Choi

Sleeping brain “calculates” what to remember and what to forget, study says

The brain cherry-picks what people remember during sleep, resulting in sharper and clearer thinking, a new study suggests.

Previous research had shown that sleep helps people consolidate their memories, fixing them in the brain so we can retrieve them later.

But the new study, a review based on new studies as well as past research on sleep and memory, suggests that sleep also transforms memories in ways that make them somewhat less accurate but more useful in the long run.

For example, sleep-enabled memories may help people produce insights, draw inferences, and foster abstract thought during waking hours.

“The sleeping brain isn’t stupid - it doesn’t just consolidate everything you put into it, but calculates what to remember and what to forget,” study leader and a cognitive neuroscientist at the University of Notre Dame in Indiana Jessica Payne said.

Emotional memories stick

For instance, the memory details that seem to get remembered best are often the most emotional ones, Payne said.

Payne and colleagues found that when people are shown a scene with an emotion-laden object in the foreground - such as a wrecked car - they are more likely to remember that object than, say, palm trees in the background, especially if they are tested after a night of slumber.

Rather than preserving scenes in their entirety, the brain apparently restructures scenes to remember only their most emotional and perhaps most important elements while allowing less emotional details to deteriorate.

Measurements of brain activity support this notion, revealing that brain regions linked with emotion and memory consolidation are periodically more active during sleep then when awake.

“It makes sense to selectively remember emotional information - our ancestors would not want to forget a snake was in a particular location or that someone in the tribe was particularly mean and should be avoided,” said Payne, whose study appeared in the October issue of the journal Current Directions in Psychological Science.

“Memories are not so much about remembering the past as being able to anticipate and predict multiple possible futures.”

Selective memory’s dark side

But there are dark sides to such selectivity. For instance, the brain can focus on remembering negative experiences at the exclusion of others, which occurs in depression and post-traumatic stress disorder.

Future research may shed light on what details are remembered and how they’re remembered, which could help deal with trauma, Payne noted.

National Geographic News