Mice Make Memories While They Snooze: Sleep and The Brain

Of course, a good night's sleep plays a critical role in our daily function, but what's exactly going on as we sift in and out of dreamland? A lot of memory-making, according to researchers at New York University (NYU).

When Wen-Biao Gan, a neuroscientist and physiologist at NYU, watched mice sleeping, he discovered that the animals' brains are quite active. The flurry of nerve cells in their organs showed what's really going on as these creatures sleep: an active consolidation of memories.

"Finding out sleep promotes new connections between neurons is new, nobody knew this before," says Gan, via BBC.

"We thought sleep helped, but it could have been other causes, and we show it really helps to make connections and that in sleep the brain is not quiet, it is replaying what happened during the day and it seems quite important for making the connections."

For the study, published in the journal Science, researchers had mice run on a rotating and accelerating rod. Shortly after, they allowed them to sleep. However, while some of the mice were allowed to sleep undisturbed, others were kept from quality sleep cycles.

For those who received untroubled rest periods, they showed signs of stronger neural connections following just the non REM sleep cycles. 

"My feeling is that sleep is important to the process of forming long term memory," says Gan, via TIME.

Researchers found that during REM cycles, nerve connections that the mice made were reactivated. However, when the reactivation of the nerves was blocked, no new connections could be made. This suggests that making long-term memories is more of a two part process in which sleep plays a critical role.