After pulling an all-nighter or subsisting on mere hours of sleep, you may feel a dense fog has settled in your brain. Every part of you wants to acquiesce and let your heavy eyelids close and your aching body rest.

Imagine existing in a sleep-deprived state for several years, yet needing to learn and perform techniques that require incredible dexterity and diagnoses that mandate a deep clarity of thought.

This perpetual tiredness appears to be common for residents and interns who, at one time, trained more than 100 hours per week, but today work closer to 80 hours—still double what’s expected in the standard 9-to-5 job.

As detailed in my last blog, just over a decade ago, when study upon study emerged showing the link between sleep deprivation and medical errors, the Accreditation Council for Graduate Medical Education (ACGME) stepped in to help alleviate the burden by cutting work hours by 20%, or the equivalent of one year of training. This regulation, however, opened the door to a new set of worries.

Here, I examine the latest research on sleep—why it’s important for memory and how we can take some shortcuts to get the most out of our limited slumbering hours.

As Robert Stickgold, MD, PhD, associate professor at Harvard Medical School and Beth Israel Deaconess Medical Center in Boston, and Jeffrey M. Ellenbogen, MD, director of The Sleeping Brain lab and assistant professor of neurology at Johns Hopkins University, wrote in Scientific American Mind in 2008:

"The latest research suggests that while we are peacefully asleep our brain is busily processing the day’s information. It combs through recently formed memories, stabilizing, copying and filing them, so that they will be more useful the next day. A night of sleep can make memories resistant to interference from other information and allow us to recall them for use more effectively the next morning. And sleep not only strengthens memories, it also lets the brain sift through newly formed memories, possibly even identifying what is worth keeping and selectively maintaining or enhancing these aspects of a memory."

But how exactly sleep enhances learning and memory is still not completely understood. Perhaps, the authors suggest, when we sleep our brain can mull over the activities of the previous day, reactivating those neural connections and consequently strengthening them.

In fact, the brain continues to learn and make new associations while we sleep. In a 2007 study, Dr. Ellenbogen revealed that our brain requires time to process new material and link together ideas in novel ways. These connections become most robust after a night of sleep, he found. Research also reveals that sleep enhances our ability to think creatively. Psychologists at the University of California, San Diego, reported that Rapid Eye Movement (REM) sleep not only improved learning, it also facilitated creative problem solving.

Although a full night’s sleep is ideal for learning and memory, naps can also impart many of the same benefits. Research examining physicians and nurses who worked three consecutive 12-hour night shifts found that napping for 40 minutes enhanced alertness, attention and efficiency compared with the group that didn’t nap. For people who work night shifts, a nap can even save lives. In a 2004 study analyzing data on highway car accidents, researchers found that napping before a night shift reduced the risk of accidents by almost half.

If 40 minutes is too much time to spare for a nap, just 10 minutes dozing can improve performance. According to recent research, a 10-minute nap can produce immediate improvements in subjective sleepiness, fatigue, and cognitive performance and is not associated with the post-nap grogginess that often comes with longer naps.

The timing of sleep after learning may impact learning and memory as well. In one study, 200 participants memorized related and unrelated word pairs, such as“fire and smoke” or “insect and truth” and researchers tested their retention at varies intervals. After a 12-hour interval, participants who slept performed better on the recall test. Perhaps more importantly, after a 24-hour interval, participants who slept immediately after learning recalled significantly more than those who were awake for a full day before sleeping. The authors concluded that we may retain the most if we sleep soon after learning new information.

But what happens to the brain when it’s sleep-deprived? Todd Maddox, PhD, Wayne Holtzman Chair and professor of psychology in the 
Department of Psychology at the University of Texas, Austin, has tried to unravel how the brain becomes impaired after no sleep. He and colleagues found that sleep-deprived participants became less inhibited and were more likely to make riskier decisions, a potentially dangerous side effect for sleep-deprived surgical trainees who often deal with sensitive, sometimes life-or-death, situations.

Although evidence is just emerging in this area, it may be possible to train the brain to improve memory during sleep. A study published in Nature Neuroscience in 2012 found that information gleaned while awake may be enhanced at bedtime. Here, researchers had participants learn to play two melodies on a keyboard and researchers then played one of the tunes while participants napped. When they woke, volunteers could perform both tunes with greater accuracy post-nap, but did significantly better with the ditty played during their nap, despite being unaware of the music.

Another study in Science supports the idea that sound cues played during sleep can help consolidate memories. Scientists at Northwestern University taught participants to move 50 pictures to their correct locations on a computer screen, where each picture came with a related sound. Participants who had these related sounds played, unbeknownst to them, while they napped performed much better on the memory task. Thus, perhaps, it is possible to get some study time in while we sleep.

Although the literature clearly shows that sleep is essential to learning, memory and even rational decision making, it is impossible for surgical trainees to get the recommended eight hours every night, even with the work hour restrictions. But perhaps by better understanding the effect sleep has on the brain, working in a cross-disciplinary manner with sleep researchers, and integrating certain strategies into the life of residents and interns can help mitigate some of the problems associated with sleep deprivation and, at the same time, bolster learning and memory.