How Sleep Helps Us to Remember and Forget at the Same Time

Posted on September 29, 2017

Extensive research on memory has shown that it is deeply connected to sleep. For example, neuroplasticity (the brain’s ability to retrace new connections and pathways between neurons that enable us to learn new information) is heavily dependent on sleep.

However, scientific literature on the ability to learn while we are asleep shows mixed results. Some studies suggest that our brains have the ability to learn during sleep, while others produce evidence of the opposite. Thomas Andrillon, Ph.D., and his team from the École Normale Supérieure (ENS) and the Paris Descartes University hypothesized that the reason why different studies got different results is that they studied different sleep phases, each with a different effect on learning abilities.

Using readings from the EEG, the researchers looked at three sleep phases: rapid eye movemet (REM) sleep, light non-REM (NREM) sleep, and deep non-REM sleep.

REM sleep accounts for around 25% of any sleep cycle, and occurs around 70 to 90 minutes after you fall asleep. NREM on the other hand has several substages, and because of the different brain waves associated with these different sleep phases, an EEG is able to detect when a person is entering a specific sleep phase. An EEG can also measure whether the brain is responding to new auditory information (a sequence of sounds) or to information that has already been learned in the past.

As hypothesized, the research team revealed significant differences between the three sleep phases: According to the EEG marker, during deep NREM sleep, the brain seems to not aid learning as well as suppress it. They concluded that the role of deep NREM sleep is to suppress previous learning, otherwise useless information would back up and overwhelm our brains’ capacities.

In an interview with Medical News Today the study’s first author said that "[the] biggest surprise came from brain's ability to unlearn. Thus, it seems that during sleep, we can either form new memories, learn, or do the reverse: suppress memories and unlearn."

You could say the study was able to harmonize two previously disagreeing theories: one suggesting that sleep’s main function in memory is to consolidate newly acquired information, and the other saying that sleep is a way of discarding useless information.

Category(s):Learning Difficulties, Other

Source material from Medical News Today

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