REM sleep is thought to be related to the forming of memories, but until now nobody has been able to prove it, or explain exactly how it happens. Now, in mice at least, the mechanism has been discovered and tested.
REM (rapid eye movement) sleep is dream sleep, and researchers from McGill University and the University of Bern have successfully demonstrated that not only is REM essential for the consolidation of new memories, but also managed to actually switch off newly formed memories in mice.
The researchers, led by McGill PhD student Richard Boyce, trained mice to spot a new object that had been added to their controlled environment. Mice spend more time sniffing around the new object than they do the existing ones.
Later, when the mice were in REM sleep, dreaming of cheese, the team used light pulses to switch off neurons in the hippocampus area of the brain, specifically the neurons used to consolidate new memories.
The following day, the treated mice did not remember the new object placed the previous day. Importantly, "disrupting the same system for similar durations during non-REM sleep or wakefulness had no effect on memory," writes Boyce.
This, say the researchers, demonstrates that the silenced neurons are required, specifically during REM sleep, "for normal memory consolidation."
Apart from being a fascinating discovery on their own, the results may have important consequences for humans. Alzheimer’s sufferers, for instance, experience big disruptions in their REM sleep, which may, say the researchers, play a role in the disease’s memory-impairing effects.
Sleep, particularly REM sleep, is not only important for forming memories, but might be the very thing that sets us apart from the rest of the Earth’s apes. Humans sleep shorter, but much more efficiently than other primates, which not only freed us up to spend more time learning and bonding with our fellow humans, but also helped us to more quickly remember those skills. It could be that we conquered the world not by working, but by being really good at sleeping and dreaming.
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