If you want to learn, get some sleep

Forget the all-night cramming. If you want to learn, get regular sleep!

A recently published study suggests that sleep helps people to remember a newly learned words and incorporate them into their thinking. But the same principles are likely to apply to other types of learning. Sleep has a role to play in the reorganization of new memories.

J Tamminen, JD Payne, R Stickgold, EJ Wamsley, and MG Gaskell. Sleep Spindle Activity is Associated with the Integration of New Memories and Existing Knowledge. Journal of Neuroscience, Oct 2010; 30: 14356 – 14360.

Abstract:Sleep spindle activity has been associated with improvements in procedural and declarative memory. Here, for the first time, we looked at the role of spindles in the integration of newly learned information with existing knowledge, contrasting this with explicit recall of the new information. Two groups of participants learned novel spoken words (e.g., cathedruke) that overlapped phonologically with familiar words (e.g., cathedral). The sleep group was exposed to the novel words in the evening, followed by an initial test, a polysomnographically monitored night of sleep, and a second test in the morning. The wake group was exposed and initially tested in the morning and spent a retention interval of similar duration awake. Finally, both groups were tested a week later at the same circadian time to control for possible circadian effects. In the sleep group, participants recalled more words and recognized them faster after sleep, whereas in the wake group such changes were not observed until the final test 1 week later. Following acquisition of the novel words, recognition of the familiar words was slowed in both groups, but only after the retention interval, indicating that the novel words had been integrated into the mental lexicon following consolidation. Importantly, spindle activity was associated with overnight lexical integration in the sleep group, but not with gains in recall rate or recognition speed of the novel words themselves. Spindle activity appears to be particularly important for overnight integration of new memories with existing neocortical knowledge.

When the researchers examined whether newly learned words had been integrated with existing knowledge, they discovered the involvement of a different type of activity in the sleeping brain. Sleep spindles are brief but intense bursts of brain activity that reflect information transfer between different memory stores in the brain-the hippocampus deep in the brain and the neocortex, the surface of the brain.

Memories in the hippocampus are stored separately from other memories, while memories in the neocortex are connected to other knowledge. Volunteers who experienced more sleep spindles overnight were more successful in connecting the new words to the rest of the words in their mental lexicon, suggesting that the new words were communicated from the hippocampus to the neocortex during sleep.

New memories are only really useful if you can connect them to information you already know. For this, you need sleep.