Modern Medicine

What does sleep have to do with memory?
Answered by Discovery Fit & Health
  • Discovery Fit & Health

    Discovery Fit & Health

  1. There's a theory among certain researchers that sleep is our brain's opportunity to file away or discard thoughts and memories of events from the previous day. The theory has been tested often in recent years and studies over the past few decades have shown that adequate sleep seems to improve memory.

    In 2009, researchers at MIT used mice to show how replaying experiences from mazes while sleeping seemed to help them perform better when they returned to the mazes while awake. The mice formed cells that would fire when they moved through the maze; the cells in the hippocampus formed patterns -- or memories -- of negotiating the maze to reach the end. When the mice slept after running through the maze, the same cells fired in similar orders. Scientists interrupted the sleep and memory formation of some mice, but not of others. The ones who slept uninterrupted remembered the maze path longer than those who had broken sleep; researchers said that this showed that sleep helps form long-term memory [source: US News Health].

    Neuroscientists at Northwestern University also carried out a small study to see if we could take advantage of the sleep-memory connection by using sleep to help improve short-term memory -- and why not make the most of time spent snoozing? After showing 12 participants 50 images on a computer screen, along with a sound that related to the object (such as a meow sound when a cat popped up), the researchers sent the group to another room for a nap. Using caps fitted with electrodes, they could tell when each participant entered deep sleep; they then played the related sounds of half of the objects at a very low volume. When the participants awoke and were asked to recall the positions of the objects on the computer screen, they did slightly better at locating those objects associated with the 25 sounds played than they did locating the other objects. Some of the short-term memories likely consolidated with the sleep-time reminders [source: Narayan].

    Even without audio reminders, many neuroscientists agree that during deep sleep, our brains replay the day's events and strengthen memories. The brain probably orders factual memories, like names and dates, during deeper sleep and memories related to emotions and motor skills during rapid eye movement, or REM, sleep. Some neuroscientists say that the brain's relationship to memory has less to do with filing and ordering memories and more to do with letting the brain rest from the hard work neurons do all day.  This would not explain, however, why recorded cues help improve short-term memory. There is no doubt research on sleep and memory will continue.

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