Sleep's role in memory has been discovered using advanced microscopy. Researchers witnessed the formation of new connections between the brain's synapses during sleep, proving the role of sleep in creating memories. Although it is well known that sleep plays an important role in memory, what happens inside the brain was unknown.
Professor Wen-Biao Gan of New York University, told the BBC: "Finding out sleep promotes new connections between neurons is new; nobody knew this before. "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."