In the first study, Sara Mednick of Harvard University and her colleagues investigated the role of sleep in perceptual learning by training subjects to report the direction of colored bars superimposed on other lines on a computer screen. Their performance progressively worsened throughout the day. If the researchers allowed individuals to nap for 30 minutes, however, the deterioration halted; a one-hour snooze enabled performance to bounce back to initial morning levels. Additionally, participants¿ functioning improved when given a new task that required a neural network different from the one used in the initial session. These effects prompted the team to posit that saturation of a particular set of connections in the brain, not general fatigue, caused the decline in performance. Upon reaching a certain threshold, the brain seems to prevent the absorption of new information in order to allow the data already there to be committed to memory during slumber. Apparently, the deep, slow-wave sleep that occurs in even short naps allows recently learned information to be processed and readies the mind for new knowledge.
In the second study, Matthew Walker and his collaborators, part of the same group at Harvard University, looked at the effects of sleep on motor learning. Subjects were taught to punch a certain sequence of keys, and they practiced the task for some time. But 12 hours later that same day, their speed and accuracy did not significantly improve. When the team trained the participants at night and retested them the next morning after a good night¿s sleep, however, their performance improved by 20 percent. Improvement seemed to be directly related to what is known as stage 2 non-rapid eye movement sleep. "This is the part of a good night¿s sleep that many people will cut short by getting up early in the morning," Walker notes.
These findings may also help answer other questions, such as why infants sleep so much. "The intensity of learning new skills and information may drive the brain¿s hunger for large amounts of sleep," Walker remarks. He adds that "in order for an individual to learn new things, they may require a good night¿s sleep before the maximum benefit of the time they spend practicing is realized." Perhaps in the future a typical day at the office will start later and include a power nap.