How Sleep and Memory Connect: A HealthCentral Explainer

ATsai Editor
  • Sleep and memory are intimately connected, and scientists are just figuring out how they work together. Here is some of the latest research on how to boost memory with sleep and sound, and how sleep affects memory.


    How can you boost your memory with sleep?


    New research from Northwestern University has found that rehearsing a memory, during sleep or while awake, can help you to remember it later. Researchers first found that with high value memories--such as making more money-- the memory is more likely to be rehearsed and consolidated during sleep. This process automatically makes it easier for us to remember it later. The scientists also found that they could manipulate sleep to make low-value memory more easily recalled by using sound stimulation.

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    For the study, participants were shown locations of objects on a computer screen, and each object was assigned with a numerical value to let the participants know how much money they could make if they remembered the object later. When each object was shown, an accompanying sound was also present.


    One example is a tea kettle and a whistling sound. The sound was played while the participants were awake and asleep, and researchers found that participants remembered the low-value associations better when the sound was played during sleep.


    Researchers believe that sleep is reactivated the information with sound, and therefore re-energizes  the memories and stores them better.


    Another recent study looked at sleep and sound stimulation to boost memory during slow wave sleep oscillations, which are critical for retaining memories. The researchers found that playing sounds synchronized to the rhythm of the slow wave oscillations enhanced the oscillations and boosted memory. They also noted that this type of therapy might also boost quality of sleep.


    For the study, researchers conducted the sound test on 11 participants on different nights. Some were given the synchronized sounds, while others were given unsynchronized sounds. The participants who had received the synchronized sounds were better able to recall word associations they had learned the night before. The unsynchronized sounds did nothing to help memory. Researchers say this might be able to enhance other brain rhythms that would be useful, such as attention span.


    How can sleep affect memory?


    Scientists have also found a connection between poor quality sleep and memory loss, particularly in the elderly. Researchers looked at the brain waves that store memories as we sleep, which transfers memories from the hippocampus to the pre-frontal cortex where long-term memories are stored. They found that when adults have poor sleep, the memories get stuck in the hippocampus and never make it to the pre-frontal cortex. This can cause forgetfulness, such as forgetting names.


    For the study, researchers looked at memory and quality of sleep in 18 young adults (in their 20s) and 15 older adults (in their 70s). Prior to sleeping, the participants were tested on 120 pairs of words, and then an EEG machine monitored their brain activity while they slept.


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    When they woke, they were tested again on the word pairs, but this time they were undergoing fMRI scans. Researchers found that deep sleep among the older adults was 75 percent lower than the younger group, which led to their memory being 55 percent worse the next day than the younger group. Researchers believe deterioration of the frontal lobe has something to do with the decline.



    University, N. (2013, April 16). "Memory Rehearsal During Sleep Can Make A Big Difference In Remembering Later." Medical News Today. Retrieved from


    Press, C. (2013, April 15). "Enhancing Memory During Sleep Using Sound Stimulation." Medical News Today. Retrieved from


    Nordqvist, J. (2013, January 28). "Poor Sleep Causes Memory Loss And Forgetfulness." Medical News Today. Retrieved from


Published On: April 19, 2013