Validity of "Let Me Sleep on it"

New research shows how sleep can help us to better remember newly learned words.

New study results from a team of researchers at the University of York and Harvard Medical School suggests that sleep can help us to not only learn a new piece of information, but also allow our brains to better file it away and make it available when needed.

Publishing their results in the Journal of Neuroscience, the researchers found that sleep helps people remember a word that they’ve just learned, as well as incorporate new words into their “mental lexicon.”

The team came to this conclusion after teaching volunteers new words in the evening and then immediately testing them. The volunteers then slept overnight in a laboratory, with brain activity recorded on an EEG. The following morning, they were tested again, and the researchers found that the volunteers could remember more words than during the test immediately after they learned the words; what’s more, the volunteers could recognize the words faster, a sign that sleep allowed for the strengthening of their new memories. When a control group was trained on new words in the morning and tested in the evening, without sleeping in between, the above results were not found.

Evaluation of EEG readings shows that slow-wave sleep, as opposed REM sleep, aided in strengthening the new memories. Involvement of sleep spindles—brief but intense bursts of brain activity that reflect information transfer from the hippocampus to the neocortex—was found after examining if new words were integrated with existing mental lexicon knowledge. Those who experienced more sleep spindles while sleeping were better able to connect the new words (stored in the hippocampus separately from other memories) to the existing words in their mental lexicon (connected in the neocortex to other knowledge), suggesting that while they slept, the new words were communicated from the hippocampus to the neocrotex.

"We suspected from previous work that sleep had a role to play in the reorganisation of new memories, but this is the first time we've really been able to observe it in action, and understand the importance of spindle activity in the process, ” said co-author professor Gareth Gaskell, Department of Psychology, University of York.

Though focused on expanding vocabulary, the principles learned in the study are likely to apply across the board in regards to learning.

“New memories are only really useful if you can connect them to information you already know,” said lead author Dr. Jakke Tamminen. “Imagine a game of chess, and being told that the rule governing the movement of a specific piece has just changed. That new information is only useful to you once you can modify your game strategy, the knowledge of how the other pieces move, and how to respond to your opponent’s moves. Our study identifies the brain activity during sleep that organizes new memories and makes those vital connections with existing knowledge.”

What impact on your practice will knowledge of how sleep helps our learning have? Should students (medical or not), and even practicing physicians educate themselves just prior to going to bed? It would be interesting to see how night students perform on tests compared to day students who complete the same tests. What other potential do these findings hold?

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