午夜福利1000集合

Maybe it鈥檚 a brutal deadline that has kept you up. Or your newborn, who didn鈥檛 let you sleep all night. Or perhaps you鈥檙e just at a club and don鈥檛 want to cut the party short.

Even those of us who love our shuteye must admit that there are times when we wish we didn鈥檛 need so much of it. Now a small group of researchers is starting to zero in on ways to squeeze a full night鈥檚 sleep into fewer hours, using technology rather than drugs. If they succeed, they could do more than help us cram more activities into our waking hours 鈥� they could, in theory, provide an alternative route to the fountain of youth.

While sleep researchers have not yet managed to reach a consensus on why we sleep (see 鈥�Sleep: Why do we need it?鈥�), they have a pretty good idea of how we do it. During sleep, complex changes occur in the brain. Some of these can be observed with an electroencephalograph, which uses electrodes placed on the skull to track the brain鈥檚 electrical activity. Your nightly 8 hours are not a single undifferentiated lump, but instead multiple cycles of four stages. We go through these sequentially; during a good night鈥檚 sleep, we鈥檒l repeat each roughly 90-minute cycle five or six times (see diagram).

Some of the stages have especially strong associations with specific functions. Stage 1 is considered the boundary between sleep and wakefulness. Its length varies from person to person and throughout the night, but it tends to lasts between 5 and 15 minutes, and its primary function appears to be to get us to the deeper stages. 鈥淵ou can think of it as the on-ramp to sleep,鈥� says Chris Berka, a neuroscientist at Advanced Brain Monitoring in Carlsbad, California.

The transition to stage 2 is sometimes disrupted by what is known as a hypnic jerk, a falling sensation that results in a violent twitch as the body鈥檚 muscles begin to relax. That relaxation makes stage 2 sleep ideal for naps. Lasting 20 minutes or so, it restores fatigued muscles and replenishes alertness, and if you are awakened during this stage, you鈥檒l feel refreshed.

Not so for stage 3. Its characteristic brainwaves on EEG lend it the name 鈥渟low-wave sleep鈥�. For reasons that are poorly understood, there is a robust relationship between . For example, , and prolactin regulates the immune system. It鈥檚 also the hardest to wake from. If you are roused, say, 45 minutes into sleep, you will feel groggy, confused and irritable. The time we spend in stage 3 varies, but it lasts about 60 minutes in the first cycle of the night, diminishing in duration with each subsequent cycle and increasingly being replaced by an entirely different phase known as rapid-eye-movement (REM) sleep. This is when the majority of dreaming is thought to take place (see 鈥�Where do our minds go at night?鈥�).

To get by on fewer of these nightly cycles, our main strategy has simply been to curtail sleep at predetermined times, courtesy of the cursed alarm clock. Get less sleep than you need, however, and say goodbye to attention, alertness, concentration, judgement and problem-solving (see graph). To reduce these effects, we鈥檝e traditionally enlisted stimulants like caffeine. It works well enough in the short term, which may explain why . However, caffeine wears off after a few hours and is subject to the law of diminishing returns.

In the late 1990s, a putative wonder drug called modafinil briefly promised to trounce caffeine. But excitement fizzled when it became clear that the restorative effects of a tablet of modafinil were equivalent to no more than a few cups of coffee. While its longer half-life meant it could be taken less frequently, with fewer gastrointestinal effects, the price 鈥� coupled with the necessary prescription 鈥� meant caffeine stayed king.

In any case, no stimulant can stave off the far more alarming physical effects of sleep deprivation. In one experiment at the University of Chicago, researchers kept rats awake continuously. . Last year, clues to the mechanism were revealed. After keeping volunteers awake for 29 hours, researchers at the University of Surrey, UK, found that their white blood cell counts . 鈥淚t is a fair conclusion that sleep loss adversely affects one鈥檚 ability to combat infections,鈥� says , at Washington State University in Pullman.

鈥淣o stimulant can stave off the alarming long-term effects of sleep deprivation鈥�

It鈥檚 not just acute sleep deprivation, however 鈥� over time, even the moderate daily shortfall most of us endure during an average working week will get us in trouble. After reviewing 15 studies of 470,000 people over 25 years in eight countries, researchers at the University of Warwick, UK, concluded that 鈥渟hort sleepers鈥� 鈥� those consistently getting fewer than 5 hours per night 鈥� increased their risk of heart disease, diabetes, stroke and even cancer. No stimulant can fix that.

As we improve our understanding of what happens during the different phases of sleep, however, it may become possible to take a more targeted approach to increasing our waking hours. 鈥淚deally you want 8 hours,鈥� says Nancy Wesensten, a psychologist at Walter Reed Army Institute of Research in Silver Spring, Maryland. 鈥淭he goal is to get the same benefits from 6 hours.鈥�

Instead of lopping off great, undifferentiated chunks, however, sleep researchers began to investigate how they might carve out the slivers deemed least important, to compress sleep to include just the critical parts. In 2008, hints emerged that these might be the deeper stages. For example, drugs that enhance slow-wave sleep . Unfortunately, trials on one such drug were halted when it was found to carry a higher incidence of 鈥減sychiatric side effects鈥�.

Twenty winks

Luckily, there was another option. 鈥淏rain stimulation techniques can do the same thing,鈥� Wesensten says, 鈥渙nly better.鈥�

Wesensten has spent her career finding ways to help soldiers face the extremes of what most of us tussle with during an average working week: they must make crucial, split-second decisions despite frequent sleep deprivation. 鈥淚鈥檓 not interested in whether someone can stay awake for five days in a row,鈥� she says. 鈥淚 want to give them well-rested levels of performance no matter how long they鈥檝e been awake.鈥�

Soldiers must attempt strategic naps in occasional 1 or 2-hour windows whenever the opportunity arises. How do you stay functional 鈥� not to mention sharp? There is a way. Dip into stage 2 sleep for as little as 3 minutes, and you can benefit from its refreshing effects ().

For many people, though, the anxiety of knowing they must sleep within a precise amount of time would be more effective than a stimulant in keeping them awake. The US Defense Advanced Research Projects Agency funded Berka to tackle this problem without pharmaceuticals, and such research may benefit us all eventually. Her team designed a device they call the Somneo mask, a thick, padded band that covers the cheeks, ears and much of the head. It carries a heating element around the eyes, piggybacking on research that shows facial warming sends people to sleep. In so doing, the mask fast-tracks the wearer through the stage 1 on-ramp, which seemingly has few inherent benefits, to enter stage 2 more quickly 鈥� albeit by only 2 minutes. 鈥淭his might not sound like much, but it鈥檚 the same reduction we see with hypnotic drugs,鈥� says Berka, such as zolpidem, which is used to treat insomnia.

More importantly, the mask鈥檚 built-in EEG monitors any changes in sleep stage. Program it to allow you exactly 20 minutes of sleep, and it will start counting only when it detects actual sleep. Don鈥檛 want to wake up groggy? If you are approaching stage 3 but don鈥檛 have time for a full sleep cycle, the mask will trip an alarm. Not just any alarm: the mask contains a blue light that gradually brightens, suppressing the sleep hormone melatonin to .

EEG monitoring will help make sure you do not wake up at the wrong time, but it cannot manipulate your brain waves to help you stay asleep or move you into deeper stages. This is where a technique called transcranial direct current stimulation (tDCS) comes in. It involves administering a weak current to a part of the brain called the dorsolateral prefrontal cortex, and can direct brain waves into an alignment that mimics specific features within the sleep cycle.

Researchers at the University of L眉beck in Germany who used tDCS on the brains of sleeping volunteers were able to shift them between adjacent phases of sleep. First, they deepened sleep by increasing slow waves at the cost of short-wave 鈥渓ighter鈥� sleep. This artificially induced slow-wave sleep appeared identical to normal sleep and, more importantly, reducing short-wave sleep seemed to have no ill effects. Indeed, the tDCS group showed improvement in subsequent memory tests 鈥� notably in the kind of memory that is encoded during slow-wave sleep (). 鈥淭here was no other functional difference between the control group鈥檚 sleep and tDCS subjects,鈥� says team member Lisa Marshall.

tDCS can also move your sleep in the opposite direction, Marshall says. In a follow-up study, the team was able to kick sleepers out of slow-wave sleep and into a lighter waveform more characteristic of stage 2 ().

Berka says a future version of the Somneo mask could include tDCS stimulation to address insomnia. However, while tDCS can help intensify or lighten sleep, Marshall notes that it cannot stimulate the brain to bypass stages 1 and 2 altogether. The method certainly cannot 鈥� 鈥渁s yet鈥�, she says 鈥� put you into slow-wave sleep at the flick of a switch.

But another technique, transcranial magnetic stimulation, or TMS, might do just that. It is strong enough that neuroscientists at the University of Wisconsin-Madison were able to use it to directly trigger deep sleep. As part of an investigation into increasing sleep efficiency, Giulio Tononi and his team fitted 15 volunteers with EEG caps, and, using an electromagnet held over the skull, generated an electrical current. This induced low-frequency pulses in the part of the brain where slow-wave sleep is generated. Every volunteer who was able to fall asleep under these conditions immediately produced slow oscillations characteristic of stage 3 sleep the moment TMS was flicked on ().

TMS therapy won鈥檛 be arriving in our bedrooms any time soon, though. The equipment is not portable, and the discomfort of lying in the machine prevented some volunteers from falling asleep at all. Still, the experiment showed that in principle, it is possible to move a person directly from sleep onset to stage 3 sleep, raising the intriguing possibility of bypassing stage 1 and 2 sleep altogether. In theory, doing so could nibble at least 20 minutes鈥� sleep off each cycle. Subtract those minutes from the whole without health consequences 鈥� a big, untested 鈥渋f鈥� 鈥� and you might be able to squeeze the mental and physical health benefits of 8 hours of sleep into little more than 6.

If it worked, such a device would effectively add a few weeks to the average person鈥檚 year 鈥� quite a startling increase. This is why some researchers think the technology is very likely to be developed in the near future. 鈥淚t鈥檒l take some mavericks to go out there and push the boundaries,鈥� says Julian Savulescu, who directs the Oxford Centre for Neuroethics in the UK. 鈥淏ut it鈥檒l happen.鈥�

And that鈥檚 exactly where he sees a problem. Should such technologies prove safe and become widely available, they would represent an alternate route to human longevity. Time that would otherwise be spent sleeping counts toward an extension of your waking lifespan 鈥� if you can afford the device, that is. 鈥淵ou come up against the fair innings argument: that we鈥檙e each allotted our three score years and ten, and then it鈥檚 time to retire,鈥� he says. 鈥淏ut if you live to 80 but have an effective life of 100, your life is much richer.鈥�

Therapeutic rest

And while Savulescu is all for human enhancement, he won鈥檛 be experimenting with his own sleep any time soon. 鈥淵ou always pay for it later,鈥� he says. In particular, bypassing stage 2 could prove problematic. While the study of stage 2 sleep has lagged behind work on other sleep stages, Marshall points to research indicating that this stage may be involved in memory consolidation.

Still, cajoling the brain into specific sleep stages may confer more unexpected benefits. Researchers are just beginning to find evidence of complicated connections between sleep and, for example, mental health and ageing. 鈥淧eople with depression have sleep patterns that look nothing like the cycles of healthy sleepers,鈥� says Berka. They spend more time in REM and stage 1 sleep during an average night. Use tDCS to nudge them into a healthy pattern, she says, and it might be possible to ameliorate the symptoms.

Then there鈥檚 ageing. 鈥淪leep deteriorates like everything else does as you age,鈥� says Wesensten. 鈥淧eople have more difficulty falling asleep, and that could account for the cognitive decline we see in normal ageing.鈥� But is caused by the decline in sleep, or is it the other way around, or something else entirely? No one can definitively answer this question, but early research hints that tDCS applied to older adults during sleep can restore some of that youthful memory retention.

鈥淒ifficulty falling asleep could account for the cognitive decline seen in normal ageing鈥�

And if finding a way to sleep like a young person, in turn, makes a person think like their younger self? The fountain of youth may have been as close as our bedrooms all along.