It may seem counterintuitive, but after an interval of sleep, we improve our memory and our abilities to perform tasks, while sleep deprivation impairs learning and memory. Researchers have even prompted students to take naps while studying. From The Secret Life of Sleep.
Years ago, a piano teacher suggested I take time off my daily practice periodically because, as she said, “for some reason, people play better after they’ve slept a night or two.” Her observation was shared by the Roman orator Quintilian many centuries before, who noted that: “[It] is a curious fact, of which the reason is not obvious, that the interval of a single night will greatly increase the strength of the memory.” Now my piano teacher’s casual observation is backed by scientific research. Studies reveal that learning improves over the course of several nights without any practice. In fact, sleep provides the equivalent of twice as much practice. We are smarter when we wake up than when we went to bed.
Most researchers agree that short-term memory is anchored and translated into long-term memory when we sleep. The process, called memory consolidation, appears to involve two simultaneous procedures: weakening rarely used neural connections and strengthening the patterns of newly formed memories by replaying them. Neuroscientist Mayank Mehta likened it to erasing the chalkboard so new messages do not overlap and get confused with old ones. Giulio Tononi and his colleague Chiara Cirelli at the University of Wisconsin-Madison propose that the large, slow waves that dominate SW sleep wash the board clean by reducing the number of active connections, while the brief bursts of faster activity, called ripples, inscribe new learning. They work together to enable new memories to stand out clearly. It seems that we forget in order to remember, and we do this best when we are deeply asleep, all is quiet, our breathing is slow, and the slate is clean.