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"So the next thing we looked at," the researcher continues, "was a different kind of test. We gave people a bunch of words, one at a time, and said, 'Memorize these.' We wanted to see what areas of the brain are involved in the memorization process."

The two slides that summarize the results of this testing paint a much more complicated picture. Instead of appearing lifeless, the brain scans taken while the sleepy people were trying to memorize the words revealed more activity than was evident when the memorizers were rested. The activity in one area of the sleepy subjects' brains appeared to expand and -- even more remarkably -- another area (in the right prefrontal cortex) that normally has nothing to do with language appeared to "come online during sleep deprivation," in Drummond's words. This increased brain activity appeared to pay off in terms of the subjects' memorizing performance: after 36 hours without sleep, they were able to memorize the list of words almost as well as when they were rested.

"Essentially, what we took from this is that -- under certain circumstances -- the brain appears to be able to compensate for sleep deprivation," the scientist says. It doesn't always happen, he stresses. If you have to do mathematical calculations while you're sleep-deprived, don't expect perfect accuracy. But for language-memorization activities, Drummond says the scans suggested that the brain has the ability to "recruit additional cognitive resources" that it doesn't normally use and "thereby allow somebody to perform reasonably well."

Since doing the initial set of scans, Drummond says he's been able to replicate the results and ask additional questions. These have included trying to find out if the compensatory responses can be predicted and what are the limits of the brain's ability to compensate. "We're extending sleep deprivation to 62 hours -- two and a half days," Drummond says. "We're scanning in the morning versus the evening, to see if that makes a difference. We're looking at people who naturally get very little sleep, say less than six hours, versus those who naturally get a whole lot -- more than nine hours -- to see if their brains are different. We're doing a lot of different things to see what's going on."

Drummond says the major funding for this work has come from the Department of Defense. "I think there's a lot of recognition in the military that they drive people very hard, and yet there's really no choice in time of war, especially now with very long range operations. You might have pilots who take off from Saint Louis and go bomb Kosovo, then come back. They really need to know what happens when their soldiers and sailors that fly aren't sleeping. And they're also very interested in the recovery process: once you push someone and don't let them sleep for a long time, how long does it take to get back to normal?"

In the case of Randy Gardner, that recovery appeared to be swift. According to Dement's account, the teenager at first slept for 14 hours and 40 minutes; then he awoke spontaneously at a few minutes before 9:00 p.m. By midnight, after giving more interviews, "He was very wide awake and decided to stay up and go to school in the morning." He slept for 10H hours the following night and for 9 hours the third. In three subsequent follow-up visits at the Naval Hospital, his normal sleep requirement appeared to be a bit less than 7 hours nightly.

Although Drummond says much remains unknown about the process of recovering from lost sleep, he points out that the body doesn't seem to need to make up every hour it loses. Rather, some parts of sleep appear more expendable than others. "Sleep comes in different stages," he says, with the most important phases thought to be the deep sleep of Stages 3 and 4 (in which the brain waves, heartbeat, and respiration become the slowest and most regular) and REM sleep (so called for the rapid eye movement that characterizes it). Drummond says when sleep-deprived individuals finally get to bed, they move quickly into the REM and slow-wave phases, spending much less time than normal in the light, early phases of slumber. They also may sleep more efficiently -- falling asleep more quickly once they're in bed and waking up fewer times in the night. "So without even getting extra hours of sleep the next night, you can recover some of what you lost."

Drummond says when the results of his initial MRI work reached publication, "Several people said to me, 'Oh, so what you're showing is it's no big deal not to sleep.' But that's not the case," he argues. "What we're showing is it's not necessarily lethal to not sleep, but the brain is definitely working less efficiently. Even if it doesn't perform completely poorly, it's still going to be slower. It's still going to be less accurate. My guess is that you also are probably less flexible. You'll tend to get stuck in a rut in terms of the way you make decisions or face problems." The consequences of these sorts of impairments can range from trivial to catastrophic: sleep deprivation has been implicated in the grounding of the Exxon Valdez oil tanker, the Chernobyl and Three Mile Island nuclear accidents, and the Challenger space shuttle explosion, among countless less spectacular tragedies.

Drummond concurs "absolutely" with the chorus of voices denouncing how little sleep most Americans get. "We've become a 24-hour society," he says. Work demands, television, the Internet, and other modern blandishments all compete for time spent on the pillow. "People seem to think sleep can be sacrificed for, quote, productivity, even though we're much less productive when we haven't slept," he notes. Various consequences have been shown to flow from partial sleep deprivation. Drummond says researchers have "shown that something like seven nights at six hours of sleep is like 24 hours with no sleep, and seven to nine nights at four hours of sleep is like 48 hours of sleeplessness." After a week of five-hour nights, "You actually get endocrine changes that look like you're developing diabetes. You don't process glucose well. You don't use insulin efficiently. You get increases in ghrelin, which is a hormone that makes you hungry.

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