On the fourth day, the students tackled the video test again. Only the students who had slept every night of the study improved their performance. They identified the correct pattern of images on the computer screen more rapidly than they had on the first day. They didn't get any subsequent training, so the improvement took place the first night while they slept, Stickgold says. Students who missed the first night's sleep failed to improve their performance, even though they had gotten two full nights of catch-up sleep and were not sleepy on the day of the retest.
Many people prepare for a training or study session by getting a full night's sleep.
But this study suggests that the night after the training also is crucial. During those eight hours of sleep, the brain, in this case, the cortex, is busy nailing down the memory of what it has learned during the day. People who interrupt that process, even with a single all-nighter, may find that the memory hasn't been stored in the cortex, one part of the brain involved in learning new material. The study looked at only a specific kind of learning. Real-life examples of such tasks include learning a piece on the piano or solving a computer glitch.