Z: The most important letter in the alphabet

by Lindsay Miller on September 28, 2012

Okay, so it’s not the most important letter of the alphabet, but one thing is certain: most of us could probably use more “Z’s” in our life. That’s right—sleep! Although it varies by person, the recommended amount of sleep for adults, according to the National Sleep Foundation, is 7-9 hours. Some (myself include) may chuckle at this recommendation, as a 9-hour-snooze is literally something we can only dream of.

Source: FreeDigitalPhotos.net

But why do we need sleep? I had a friend ask me this question recently. Like a battery, I said, we need to recharge so that we have energy for the next day. You know, we have to re-wire. I stopped myself. Frustrated by my inability to explain sleep without analogizing our nervous system to familiar technology, I set out to find an answer: what is really going on when we sleep?

We know all too well the consequences of what happens when we don’t sleep—delirium, irritability, excessive yawning, multiple trips to Starbucks—but what happens when we do sleep is a question that scientists are still grappling with. Some of the more popular theories about the function of sleep include energy conservation and bodily restoration, but one of the more prominent areas of research today has to do with the role of sleep in memory consolidation.

Memory consolidation can be thought of as the reactivation and reorganization of neural pathways created by events and experiences (short-term memories) into more “retraceable” or “memorable” pathways (long-term memories).

A 2011 Psychological Research study found that while we are enjoying our alleged “rest,” our brain is actually hard-at-work sifting out unimportant memories and reinforcing more important ones. Yup, you read that right: our brain shows preference for memories that are somehow relevant for our future expectations and plans. When subjects of the study were given information and told they would have to retrieve that information later, they were more likely to remember it after a period of sleep than were subjects who were given the same information but not expected to retrieve it. Of significance is that these groups were equally able to retrieve the information during wake intervals–the differences in memory retention emerged only after the sleep period. Strengthening the connection between slow-wave sleep, specifically, and memory consolidation was the finding that those who were expected to retrieve the information had noticeably increased slow-wave brain activity during their post-learning snooze!

So sleep helps us to remember (and forget)…but that’s not all, folks.

An even more recent study done at Northwestern University revealed that previously learned skills and information can actually be reinforced or “practiced” during slow-wave sleep. Prior to a nap, participants performed equally well on two previously-learned musical sequences. After their nap, study participants performed with greater accuracy on the sequence that researchers had played for them quietly during their slumber. Though this study only looked at musical sequences, researchers are hopeful that this effect might hold for the reinforcement of other skills and processes, such as language acquisition.

Somehow I don’t think that falling asleep on top of my organic chemistry book all those times in college had the same effect…but the message still rings clear. Sleep is of primary importance in healthy mental functioning, and committing to getting those extra few hours could make a big difference!

Having trouble falling asleep? Sick of counting sheep? Try reading this blog 5 times, and that should do the trick!




Born, J., & Wilhelm, I. (2011). System consolidation of memory during sleep. Psychological Research, 76(2), 192-203.

Antony, J. W., Gobel, E. W., O’Hare, J. K., Reber, P. J., & Paller, K. A. (2012). Cued memory reactivation during sleep influences skill learning. Nature Neuroscience, 15, 1114-1116.


Photo credits:


Microsoft Office Media Gallery