For Long-Term Memory, Sleep On It

Sleep is important for a lot of reasons, but one reason is its role in learning and memory. Scientists have known for some time now that memory doesn’t function as well without proper rest, but the reasons for this are just now starting to be revealed. New research sheds light on the mechanism of how our brain solidifies memories while we sleep.


Photo credit: David D, Flickr

Sleep is important for learning

Many of us have pulled all-nighters in college before big exams, and likely asked ourselves the next day whether it was worth it. Besides feeling poor physcially, studies in recent years have suggested that your ability to recall information is also impaired.

One study from 2012 tested the ability of volunteers to remember certain facts when learning happened at different times of day. Some of the volunteers learned the information in the morning and the other half of the volunteers learned it in the evening.  All of the volunteers were tested 12 hours later, and the study found that people performed much better when they learned the subject at night and had slept right after learning the material.

That study suggested that memory consolidation happened more readily with information that was learned right before sleeping. Memory consolidation happens when information is converted from short term to long term memory, and is necessary for learning. Other studies have shown that sleep helps to make information easier to apply later, especially in children. It has also been shown to help information better sink in, especially when there are exceptions to a rule that is being learned (such as with languages).

But why does sleep help us learn and remember better?

Sleep helps consolidate memories

More recent studies have finally begun to see that “sleeping on it” actually strengthens the connections between neurons. Research from 2014 was the first to show a real mechanism for memory consolidation. A team from China and the US found that mice that trained for 3 hours on a task but were sleep deprived performed more poorly than well-rested mice that only trained for 1 hour. Beyond just testing, the researchers actually looked directly at the neurons of the mice – and found that there were more connections between neurons of the mice that slept. They also looked at the different phases of sleep to find that deep or slow-wave sleep was where the connections were formed.

The newest research from the University of Bristol adds more to the story. By studying rats, the group found that memories are actually replayed during sleep, but at fast-forward speed. While this happens, the neural connections are strengthened, and important memories from the day are consolidated. The brain figures out which memories are important as it goes through them.

The replay activity happens in the hippocampus, where new memories are made and sorted. The hippocampus is also associated with emotions.

Lead scientist of the study, Dr. Jack Mellor, said, “These findings are about the fundamental processes that occur in the brain during the consolidation of memory during sleep. It also seems that the successful replay of brain activity during sleep is dependent on the emotional state of the person when they are learning. This has major implications for how we teach and enable people to learn effectively.

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