Sex Sleep Eat Drink Dream (2 page)

Even within an individual, variation reigns. Over the course of a day, a year, a lifetime, we are many different people. As Montaigne said, there is as much difference between us and ourselves as between us and others.

Nevertheless, we all share common body experiences. A single volume can't hope to cover them all, or even those that transpire within the confines of a single day. The choice of topics here reflects my own preoccupations, as well as guesses about what will prove interesting for others. From caress to orgasm, multitasking to memorizing, working out to stressing out, drooping to dreaming, it's here.

Morning

The brightness of a new page
where everything yet can happen.

RAINER MARIA RILKE
Book of Hours

1. AROUSAL

M
Y EYES OPEN
just long enough to fix on the clock: 5:28
A.M.,
two minutes before the alarm rings. Except for the distant fluty notes of a songbird, the world is silent. Though the stars are fading, it will be another hour before the sun's first rays creep over the horizon.

Maybe you're like me: You anticipate your alarm, wake a minute or two before it blares. It's probably not sufficient sleep that awoke you. What did, then? Some people claim that subtle aural trigger cues do the trick, those characteristic sounds of early morning, such as the start-up of noise on a highway or the passing of a delivery truck or even the little tick produced by a mechanical alarm clock just before it rings. It's true that the brain is good at processing sound while we sleep; that's why we buy audible alarm clocks. We don't buy odor alarms for equally good reason. Though some people swear they are roused from deep sleep by the putrid stink of skunk or the heady aroma of percolating coffee, a new study suggests otherwise: Scientists at Brown University documented a complete failure of response during all but the earliest phase of sleep to powerful odors such as peppermint and the distinctly noxious pyridine, a component of coal tar often used as a herbicide for firewood. Don't count on the nose as a sentinel system, say the researchers: "Human olfaction is not reliably capable of alerting a sleeper."

In any case, there's mounting evidence to suggest that the trigger cues may not be outside your body at all, but inside, in a kind of brilliant little mind-based alarm clock that prepares the brain for waking. When Peretz Lavie, a sleep researcher at the Technion-Israel Institute of Technology, investigated whether people can awaken on their own accord at a specified time without external cues, he discovered a surprise: Many of his subjects awoke ten minutes before or after the appointed time, even if it was as early as 3:30
A.M.
This is a truly remarkable feat of time-telling, which probably exceeds the ability of most people to tell time during their waking hours. Another study showed that the mere expectation that sleep will come to an end at a certain time boosts by 30 percent blood concentrations of the stress hormone adrenocorticotropin (ACTH), a sure sign that the brain is gearing up for waking.

In some of us, at least, the unconscious mind somehow keeps careful track of clock time even as it sleeps, so that the brain "expects" a timed event, such as a target wake-up time, just as it does during wakefulness, and triggers the release of chemicals designed to get us up and going. Anticipation—once thought to be an ability only of the conscious mind—may actually occur as we sleep, allowing (or dooming) us to rouse spontaneously at the same predictable hour.

Talk about mysteries!

But maybe you don't have this problem; maybe you're among the majority who awaken with a startle to the real sound of a real alarm or a burst of music or DJ chatter from your clock radio. For you, the morning ritual begins with a poke at the snooze button to steal ten more minutes of sleep. Chances are you need this—and more. In a nation that averages less than seven hours of sleep instead of the optimal eight, most people are mildly sleep deprived, especially during the work week. Unfortunately, the short bouts of sleep you nip between slaps at your clock are not restorative or restful, say specialists, but light and fragmented. Even if you doze through the next sounding of the buzzer, your expectation of awakening will affect the quality of your slumber.

There are, of course, those who will stubbornly sleep through even the shrillest alarm. For such dyed-in-the-wool dozers a patent was granted in 1855 for an ejector bed. If the snoring sinner ignored a built-in alarm, the side rail released, tilting the bed so that the slothful occupant tumbled to the floor. Only slightly more humane is an apparatus newly devised by a clever crew at the Massachusetts Institute of Technology: "Clocky," a fuzzy, spongy robotic alarm clock, rolls off the bedside table and zips away on a set of wheels to some elusive corner of the room. It finds a new hiding spot every day. The arduous act of finding Clocky, say the inventors, should prevent even the sleepiest owner from revisiting the pillow.

Oh, to lie for a minute in that borderland of wake and sleep known as the hypnopompic state (from the Greek for "sleep" and "sending away"), to let the mind drift into wakefulness and relish the lovely, slow coming on of day. Few of us have this luxury. If waking feels strenuous, that's because it is; with rising comes brief but violent shifts in heart rate and blood pressure and a peak in blood levels of the stress hormone Cortisol.

Alertness follows only slowly. The grogginess and disorientation immediately after awakening is known as sleep inertia, and nearly everyone suffers from it. "The brain just doesn't go from o to 60 in seven seconds," quips Charles Czeisler, a rhythms researcher at Harvard University. Most of us perform poorly on mental and physical tasks at daybreak compared with how we do just before retiring at night. "It's ironic," says Czeisler, "but the brain's performance in the first half hour after waking is worse than it is if you've been up for twenty-four hours." This useful piece of information was discovered the hard way by the U.S. Air Force in the 1950s. It had put in place a practice of sending pilots out to their jets on the tarmac overnight so they could sleep in their cockpits and be ready to go at an instant. The pilots were roused from sleep and told to take off; the accident rate soared, and the practice was banned.

When a team of scientists formally quantified the effects of sleep inertia in 2006, they found that the cognitive skills of test subjects were, on awakening, at least as bad as if the subjects had been legally drunk. While the worst sleep inertia is dispelled after about ten minutes, its effects may linger for up to two hours. Its severity will depend in part on the stage of sleep from which you were roused. Lavie's team found that people waking out of the stage known as rapid eye movement
(REM)
sleep can quickly orient themselves in their surroundings and tend to be more mentally nimble and chatty,
REM
sleep is a kind of portal to wakefulness, says Lavie, best smoothing the transition out of sleep. (It is also marked by intense and vivid dreaming, which may account for the fresh, lucid memory of some dreams on waking.)

On the other hand, those who are unfortunate enough to be catapulted into consciousness from deep, non
-REM
sleep by the jarring ring of an alarm are apt to be disoriented, with that "where am I?" feeling. To eliminate such rude awakenings, Axon Sleep Research Laboratories has come up with a kinder doppelganger to Clocky called SleepSmart, which monitors your sleep cycle and awakens you out of your lighter,
REM
sleep phase. A headband described as "minimal, comfortable, and sleek" is fitted with electrodes and a microprocessor, which measure your brain waves during each phase of your sleep and transmit the information to a clock near your bed programmed with your latest possible wake-up time. The clock takes care of the rest, awakening you during the last light-sleep phase before the zero hour.

Whether you hop or drag into full morning alertness also hinges on your chronotype, a kind of avian profile that describes your rhythmic nature—larkish or more like an owl. Lark chronotypes emit their music at sunrise; owls side with the night.

I once heard the writer Jean Auel say that her brain works best long after sunset. She goes to work at eleven or twelve at night, finishes up at seven in the morning, and then retires. She sleeps until four in the afternoon, when she rises and eats with her husband—his dinner, her breakfast—goes out on the town, and finally settles down to work again at midnight. She claims this extreme owlish "shadow" life takes no toll.

Such is the pattern, too, for the great geneticist Seymour Benzer, whose often nocturnal studies of mutant fruit flies helped unravel the genetic basis of our daily body rhythms. Benzer's working day is the middle of the night; he says he risks accident if he's forced to start work when most people do, in the morning.

At the other end of the spectrum from Auel and Benzer are extreme larks, those partial to the bright work of bakeries, who fall asleep as early as 7 or 8
P.M.
and awaken full of verve at 3 or 4
A.M.
The two extreme chronotypes can seem as different from each other as people born in different centuries or on different sides of the planet, the larks stirring just as the owls are falling asleep. The "birds" differ dramatically in peak alertness (11
A.M.
for larks, 3
P.M.
for owls), heart rate (11
A.M.
for larks, 6
P.M.
for owls), and in favorite mealtime, favorite exercise time, and daily caffeine use (cups for larks, pots for owls).

Till Roenneberg, a chronobiologist at the University of Munich, has found that extreme owl types are three times more common than extreme larks. Most people fall somewhere in between, with a leaning toward mild to moderate owlishness—a pattern that often fails to fit well with work routines, leading to feelings of "social jetlag." You can assess your own status by taking a simple questionnaire devised by Roenneberg's team, which asks such questions as: What time do you normally awaken on workdays? On free days? When do you feel fully awake? At what hour do you have an energy dip?

It should be noted here that despite the many proverbs praising the virtues of larks (Benjamin Franklin's "Early to bed, early to rise," "The early bird gets the worm," and so on), science suggests that there is no health or monetary advantage to being an early riser, nor is it necessarily a sign of mental well-being. Some time ago, a group of British researchers set out to substantiate Franklin's gnomic wisdom using data collected from more than 1,200 elderly men and women. But after examining the effects of bedtimes and waking times on health, material circumstance, and cognitive function, the researchers found that owls were in fact more often wealthier than larks, and there was little difference in the health and intelligence of the two.

In any case, you may have little choice in which bird you resemble. The daily habits of larks and owls are not a result of differences in personality, as once believed, but in the nature of our internal biological clock. Almost a decade ago, Hans Van Dongen of the University of Pennsylvania demonstrated that the biological clock of average morning types is more "phase advanced" than the clock of evening types—that is, it runs earlier, by as much as two hours. Although you might be able to overcome your proclivity, says Van Dongen, you probably can't change it. Your larkishness or owlishness is likely built right into your biology.

"Time is the substance I am made of," wrote the Argentine novelist Jorge Luis Borges. There's a deep hunch here. As biologists have learned in the past decade, time permeates the flesh of all living things—and for one powerful reason: We evolved on a rotating planet.

To understand this, think back billions of years, to an earlier world where all organisms are single-celled and floating in some warm, primitive sea. The bright sun of midday cycles with the dark cool of night, day after day, periodically, predictably, for trillions of days. Light and dark, warmth and cold: In the matrix of these daily ups and downs, ins and outs, life unfolds. With no screen of ozone in place, ultraviolet radiation damaging to life bombards the earth's surface during daylight. To avoid the harmful rays, organisms limit certain fragile or sensitive biochemical processes to the dark asylum of night, generating a rhythmic metabolism. Some evolve sensors to discern the occurrence of sunlight, at first mere light-sensitive cells, and later, sophisticated eyes that help them detect the subtle transitions of dawn and dusk.

Then comes the genius. Some life forms develop genes, cells, and bodily systems capable of generating their own internal daily rhythms beautifully attuned to planetary time, known as circadian rhythms (from the Latin
circa,
about, and
dies,
day). Pathways evolve from their light sensors to these circadian clockworks to help synchronize the internal rhythms with the solar day. "In this way," says the biologist Thomas Wehr, "the circadian pacemaker creates a day and night within the organism that mirrors the world outside."

So sensitive are these pacemakers to light that even low illumination adjusts and resets them. Sunlight is their dominant
zeitgeber,
or time giver; it sets their rhythms so they remain in tune with—or entrained by—shifting patterns of daylight and darkness, so that in summer, biological day is long, and in winter, it is short. When you pull up the shade in the morning, special light-sensitive cells in your retina measure the brightness and register dawn in the dark cradle of your brain, aligning your circadian clock to cosmic rhythms.

Yet so robust and reliable are the pacemaker's rhythms that they run continuously and persist even in the absence of environmental cues. Science has discovered this through studies in which subjects are isolated from environmental cues for weeks at a time. With no clue to the turn of day and night, their bodies start to decouple from the solar cycle but adhere to a twenty-four-hour cycle of waking and sleeping and other body rhythms. (These persistent daily patterns are known as free-running rhythms and are hard-wired into a species' genome.)