Sex Sleep Eat Drink Dream (19 page)

What might have triggered the bloom of new brain cells? The researchers found that exercise spurs the growth of capillaries around the brain, which increases blood flow, raises oxygen levels, and boosts amounts of brain-derived neurotrophic factor, or BDNF, a molecule so important in helping brain cells grow and thrive that the neuroscientist Carl Cotman calls it "the brain's wonder drug." The brain cells of the running mice also showed evidence of more synaptic plasticity, that mechanism vital to learning and memory.

"It's reasonable to speculate that the same brain changes observed in rats and mice in response to exercise may also underlie some of the improvements we see in cognitive processes in adult humans," says Art Kramer, a psychologist at the University of Illinois and an expert on the mental benefits of physical fitness. Indeed, new evidence suggests that exercise not only sharpens people's thinking, it can moderate—even halt—the cognitive decline that often comes with age.

This really is excellent news, especially given that so much new research points to the ways in which age sabotages the brain. Not long ago, Naftali Raz of Wayne State University and his colleagues measured five-year changes in the volume of particular brain regions in healthy adults. The team found widespread shrinkage, though it varied across regions. Substantial diminishment occurred in the cerebellum—that "little brain" behind the brain stem that manages movement, balance, and posture—as well as in the hippocampus, crucial for memory.

It's not clear how these changes in the size of brain regions relate to the deterioration of cognitive function that comes with older age. But the failings are all too apparent. As life slopes down from the twenties, so goes working memory, perceptual speed, quick processing of new information, the ability to resist distractions. As we grow older, we have more difficulty picking up new skills and more trouble comprehending texts, finding the right word (the tip-of-the-tongue phenomenon), and remembering the names of friends and acquaintances. This is not senility or dementia, but normal cognitive aging. Even my father, sharp as ever in his mid-seventies, admits he needs a bumper sticker reading "I brake for names."

Tim Salthouse of the University of Virginia believes that the gradual falling off of mental performance may be due to the brain's slowed processing of lower-level stimuli. If the mind is slogging slowly through basic incoming information, it has less time to spend on more complicated thinking tasks, such as the ability to plan, make decisions, multitask, update information, block out the din of the irrelevant, and sift through memory. "But just why mental processing slows with increasing age isn't clear," says Salthouse. "Maybe there's a loss of neurons, which results in more neural detours, or maybe there are age-related reductions in the quantity of neurotransmitters or a degeneration of myelin, the sheathing around neurons that's involved in communication between them."

Fortunately, exercise offers hope. One big Canadian study showed that physical activity over a lifetime is linked with lower risk of cognitive impairment and dementia of any type. The link was especially strong for women. This was confirmed in 2004, when researchers at Harvard studied exercise patterns and mental performance in eighteen thousand older women who are part of the Nurses' Health Study at the Harvard School of Public Health. Women who walked or engaged in other regular exercise did better on memory and other cognitive tests than women who were less active; in fact, said the team, the exercising women performed as if they were three years younger. Physical activity in middle age may be critical to this protective effect. Studies show that older people who exercised at least twice a week when they were middle-aged were 50 to 60 percent less likely than their sedentary counterparts to develop dementia or memory loss. The exercise seemed to benefit particularly those who carried the gene associated with a bigger risk of Alzheimer's in old age.

Art Kramer and his colleagues recently investigated the changes that occur in the human brain with exercise. Their study showed that physically fit subjects had less age-related shrinkage of brain tissue in areas critical to memory and learning than did less active subjects, and that fit seniors had more intense blood flow in frontal brain areas that are normally associated with attention in younger brains. Previous imaging studies have revealed that the young use these frontal brain regions to complete a variety of cognitive tasks. As we age, our brains show less specificity in carrying out these same tasks—possibly because we're recruiting new brain regions to compensate for losses in the efficiency of our neurons in these areas. "Perhaps cardiovascular exercise, by boosting blood flow, helps our brains turn back the clock, biologically speaking," says Kramer, thus restoring the efficiency of those areas we rely on when we're young.

Think of it as you're cooling off after a hard workout: The mind that initiates your swim, your run, your vigorous row, is itself altered, enhanced, protected by the rush of blood and changed body chemistry it originally set in motion.

Evening

If you can get through the twilight,
you'll live through the night.

DOROTHY PARKER

9. PARTY FACE

D
USK, THE HOUR
between dog and wolf. You're finally home from work, well exercised or not, and perhaps still feeling a little stressed. To leave behind the cares of the day, you may try the route to forgetting suggested by Shakespeare's Julius Caesar: "Give me a bowl of wine. In this I bury all unkindness." The end of the workday is as good a time as any to have a drink. Tolerance of alcohol peaks now, just in time for the cocktail hour. Time of day influences how quickly alcohol is metabolized and how much it affects different target organs and body functions. Alcohol ingested early in the day is more intoxicating than the same dose at twilight. In one study of twenty men, those who received a large dose of vodka at 9
A.M.
performed worse on tests of reaction time and psychological functioning than did those who received the same dose at 6
P.M.

Steal a moment before you head off to an office party and sit with your wine or gin to watch the dwindling light. I love this time of day: the gloaming, crow time, transit into night, when clarity of form dissolves, when everything near becomes distant and blurred with failing light. The body delights in thresholds, the poet Theodore Roethke tells us. It relishes the sweet coming-out of sleep or falling into it and this thing we feel at the cusp of evening. The ruddy sun limning the horizon helps to dissolve tensions and slow the hour.

This time of day may in fact affect your perception of the ticking minutes. In the late afternoon and early evening, when body temperature peaks, the passage of time seems to slow a little. To the interval timer in the brain, a minute in real time may feel several seconds longer.

Drugs such as marijuana and hashish have a similar time-expanding effect. William James wrote about the "curious increase" in felt time that comes with hashish intoxication. "We utter a sentence, and ere the end is reached the beginning seems already to date from indefinitely long ago. We enter a short street, and it is as if we should never get to the end of it." That glass of wine or gin, on the other hand, may make time fly. Alcohol reduces felt time compared with clock time, possibly by preventing the brain from receiving as many sensory inputs per second.

Whether booze buries any unkindness, however, is a topic of much debate. Depending on the particulars, on person and situation, alcohol can either lessen stress or intensify it. A key factor may once again be timing. If you consume alcohol before the onset of a stressful event, the drink may reduce its impact, says Michael Sayette of the University of Pittsburgh—for the very good reason that the booze prevents you from fully experiencing the event. It's called alcohol myopia. Intoxication disrupts the brain's ability to appraise new information and to link it with stressful associations. In other words, a traumatic event after a cocktail may feel less nerve-racking because the drink ensures that you don't quite know what hit you.

Alcohol myopia can also relieve anxiety and depression
after
a stressful occurrence, says Sayette, as long as the alcohol is paired with some kind of distraction, such as a party. The combination quite literally keeps your mind off your worries. Without such distraction, drinking alcohol after the fact can have the reverse effect, exacerbating stress—dubbed by one investigator the crying-in-your-beer effect.

So much depends on dose. That first drink makes us cheery and talkative, perhaps a little unsteady on our feet; the second or third slurs our speech, disrupts perception, affects our body sway, and impedes our ability to notice our own mistakes. It all comes down to our blood alcohol concentration, or BAC, the ratio of alcohol to blood in the body. This, in turn, is governed by how fast we drink, as well as how rapidly the alcohol is absorbed into the bloodstream and the rate at which the body distributes and metabolizes it.

There are cold-potato formulas. BAC is usually expressed as a percentage, reflecting grams of alcohol per deciliter of blood. (For example, .08 percent is equivalent to .08 grams per deciliter, a ratio that would make most of us feel pretty drunk.) After a person starts drinking, the time it takes to reach peak BAC can range anywhere from ten to ninety minutes. An hour after consuming two beers on an empty stomach, a 160-pound man may reach a BAC of about .04 percent.

I can enjoy a couple of drinks in an evening. But beyond this, my body cries out, "No more!" My low tolerance is fairly typical of my sex. Women reach higher peak blood alcohol levels than men after consuming equal doses of alcohol and become intoxicated with less drink. It was once thought that this gender difference was a simple matter of size or body weight: Women, generally smaller in stature than men, reach a higher BAC with less alcohol because there is only so far for the stuff to go. In a big body, the liquor travels farther, grows dilute, and loses its potency—certainly in a man as big as, say, two hundred pounds. But according to work by scientists at Stanford University, the real divergence results from the makeup of body mass in men and women, and perhaps some gender differences in chemistry. Women have proportionally more body fat and less water than men of the same body weight. Because alcohol is dispersed in the body's water, women—with their lower volume of water—reach higher alcohol levels than men after consuming equal amounts. Also, women may break down and eliminate alcohol and its byproducts less efficiently.

But BAC is influenced by a host of factors beyond gender and body makeup: whether your stomach is empty or full, for instance (a full stomach slows absorption); and how much sleep you've had (in the sleep-deprived, alcohol hits hard, so that one drink may seem like two).

The moderate level of drinking recommended by most experts means one standard drink (a beer or glass of wine) a day for women, two for men. To keep dog from morphing into wolf, wrote the poet George Herbert, "drink not the third glass, which thou canst not tame when once it is within thee."

It's early evening. You've arrived at your party and begun to mingle in the crowded room, launching into a lively discussion with a colleague. Though you've had only a single glass of wine, your mind fails you when an acquaintance approaches: In the midst of introductions, you temporarily blank on his name. It's there, tantalizingly, on the tip of your tongue, but you can't for the life of you retrieve it, and you stand awkwardly for a moment before mumbling, "You two know each other?"

William James described this failure as a kind of intensely active gap in our minds: "A sort of wraith of the name is in it, beckoning us in a given direction, making us at moments tingle with the sense of our closeness and then letting us sink back without the longed-for term." It's one of the "seven sins of memory" described by Daniel Schacter, a psychologist at Harvard University. Schacter's research suggests that this particular active gap is rooted in the absence of meaning in most proper names, which he calls the baker/Baker effect. If I tell you I'm a baker, he says, I'm giving you information about what I do and how I spend my time, which helps build a house of memory. If I tell you my name is Baker, I'm just providing a meaningless term. This means that the memory is isolated, bereft of mental ties or links, and so is vulnerable to temporary forgetting.

Here's where some kind of association strategy may come in handy, linking a name with an animal or object. Or perhaps a technological solution to the dilemma, like the one devised by Hewlett-Packard: a special cell phone headset fitted with a small camera that focuses on your field of vision and connects via the cell phone to your personal computer, where it accesses a database of photos and names. Once it fixes on a face, it jogs your memory with a vocal prompt.

We often forget names; we rarely forget faces. Survey the sea of people at your party, and you can spot those you know in a fraction of a second. This gift for instantly recognizing familiar faces in different contexts, regardless of view, age, light, and pose, is an astonishing perceptual achievement. Machines generally fall short at the task. "Real world tests of automated face-recognition systems have not yielded encouraging results," writes Pawan Sinha of the Massachusetts Institute of Technology. By way of example, he cites one test of face-recognition software designed to identify passengers with terrorist links. The system had a success rate of less than 50 percent, and some fifty false alarms for every five thousand passengers.

The philosopher Ludwig Wittgenstein called the face "the soul of the body," and Shakespeare called it "a book where men may read strange matters." No, wrote Milan Kundera, the face is only an "accidental and unrepeatable combination of features. It reflects neither character nor soul, nor what we call the self." In any case, faces are a currency of social exchange, and the ability to recognize them is a vital skill. "This man" becomes "my friend" or "my husband." We all have momentary failures—when we stand in blank unrecognition as someone greets us at a party as if we were old friends. For most of us these are mere temporary lapses. But there are some who suffer permanent face forgetfulness.