Think Smart: A Neuroscientist's Prescription for Improving Your Brain's Performance (7 page)

Sleep specialists have confirmed what all of us have experienced at one time or another: Sleep deprivation wreaks havoc on our mental and physical health. The risks of heart attacks, stroke, and mental breakdowns (especially among people with bipolar disorder) all rise when people are deprived of adequate sleep.

Yet sleep deprivation is a common problem even among “normal” people. Advertisements for prescription sleep aids (43 million prescriptions written per year) make up a goodly proportion of television commercials. With 26 million people working as shift workers (20 percent of whom simply can’t tolerate such a work schedule and eventually give up their jobs), the disruptive effect on the brain’s normal rhythms is a nationwide challenge.

Thanks to PET scans we now know what is going on in the brain of insomniacs. Even after finally getting to sleep the insomniac brain shows heightened activity in the arousal circuits. And since this activity prevents deep restorative sleep, insomniacs experience daytime problems in learning, memory, concentration, and mood. Indeed, psychiatrists are now speculating that insomnia, a frequent accompaniment of depression, may be the
cause
rather than the result of depression. In support of this theory, depressed people recover more quickly if, as part of their treatment, they are given sleeping pills along with an antidepressant instead of only an antidepressant.

Even among insomniacs who are not clinically depressed, sleeplessness leads to fretfulness and worry about things that next morning are recognized as not worth fretting over. Think back to the last time you had trouble getting to sleep. Odds are you weren’t lying there in a relaxed frame of mind while thinking how wonderfully everything was going in your life. More likely you were running one or another personal doomsday scenario through your mind.

“People are not awake because they are worrying, they’re worrying because they’re awake,” according to Michael L. Perlis, director of the sleep and neurophysiology laboratory at the University of Rochester. In other words, insomnia creates a worried, anxious frame of mind rather than serving as one of its symptoms. In such a state your brain is unable to restore and refresh the local brain circuits involved in memory.

Insomnia is such a debilitating problem because disturbed sleep, with the accompanying daytime sleepiness, is incompatible with optimal brain functioning. So if you suffer from insomnia, take the necessary steps to resolve it. Start by seeking professional help to find out if you suffer from some of the easily treatable causes of sleep disruption such as obstructive sleep apnea. Devices exist that can normalize breathing patterns and restore restful, refreshing sleep. If after investigation a specific cause isn’t found, you are likely to benefit from occasional use of sleeping pills. Medications are on the market now that target different neurotransmitters while exerting minimal effects on the normal brain wave patterns associated with normal sleep.

After you’ve resolved your nighttime sleep problems you can use naps as an additional brain enhancer. A daytime “power nap” will produce nearly as much skill-memory enhancement as a whole night of sleep, according to the findings of Mathew P. Walker.

In an experiment testing finger dexterity, Walker taught student volunteers skilled finger movements similar to piano scales. After learning the movements half of the students took a sixty-to-ninety-minute nap while the others remained awake and continued with their day. When retested later that same afternoon, those who napped did 16 percent better than those who did not nap.

“A daytime power nap produces nearly as much off-line memory enhancement as a whole night of sleep,” Walker told me. In order to do this, the brain selectively increases brief bursts of electrical activity called “sleep spindles.” Walker believes that these spindles trigger chemical reactions within brain cells that “instruct” specific brain circuits to strengthen connections, and thereby enhance memory.

“The brain selectively increases spindle activity in local brain circuits, thereby discretely targeting those regions in the brain that have recently formed new memories. Sleep spindles appear to make a selective and critical contribution to improving our motor memories at night and across power naps during the day,” said Walker.

Fortunately, the benefit of naps isn’t confined to learning motor skills, because most of the things we want to remember involve facts, words, and concepts rather than motor skills.

In an experiment confirming this, Mathew Tucker at the City University of New York asked volunteers to memorize pairs of words. They were then tested immediately afterward and a second time six hours later. Those who had been allowed a nap of less than one hour (far too short a time for REM sleep to occur in the normal person) scored 15 percent better than the nonnappers.

Naps play an especially critical role in the lives of highly creative people. When performance psychologist K. Anders Ericsson examined the diaries of expert musicians, he found that most of them could engage in concentrated focused practice for only around an hour. After that, their concentration began to falter and their performance declined. To compensate for this turndown in performance, they spent more time napping. These recuperative naps restored their ability to maintain the high levels of concentration required for their creative efforts.

At this point you’re probably wondering: But how do I force myself to fall asleep for a nap less than an hour long? And doesn’t taking a nap make it more likely that I’ll not be able to get to sleep later that night?

Sleep can’t be forced. It has to flow naturally from a state of relaxation and surrender. Indeed, sleep involves a paradox: The more effort you expend trying to fall asleep, the more awake you become. Instead of trying to force yourself to sleep, you should set an alarm for thirty minutes (or ask someone to awaken you after that time) and lie down with the intention of simply relaxing. After a few days of doing this, you’ll find yourself drifting off into a brief but refreshing sleep. I discovered this several years ago when I was teaching an evening course on the brain at the Smithsonian Institution in Washington, D.C.

My lecture, and the questions-and-answers following, went on from six to eight p.m. As I discovered, that schedule proved exhausting, especially on busy days when I was already beginning to feel fatigued after a day in which I wrote from seven to nine a.m., then treated a steady stream of patients from ten until four. In order to recharge my energy before my lecture, I decided to try simply turning off the lights in my office at four-thirty and resting on the couch.

The first few attempts at napping were failures. I didn’t fall asleep and didn’t feel any less tired when I got up. But I kept at it and after a few days of simply “relaxing” and not trying to “make myself” fall asleep, I started drifting into a light sleep within minutes of lying down. Now I can fall into a light sleep for fifteen or twenty minutes almost every time I lie down. Most important, I can deliver evening lectures without feeling fatigued and still remain fully engaged afterward with questions from the audience.

The second question—Do daytime naps interfere with sleep later that night?—requires a more nuanced answer. Yes, if a nap goes on too long it does interfere with sleep quality and duration later that night. That’s why I suggested resolving any nighttime sleep difficulties before establishing the nap habit. In general, a nap lasting more than an hour is probably too long. The key is to find your own personal cutoff point separating a nap that increases your mental sharpness from one that makes you feel groggy upon awakening and, later that night, results in insomnia.

In addition, if a nap goes on for too long, cognitive performance immediately after the nap is worsened rather than improved. Your personal optimum nap length is best estimated by gauging how you feel after the nap. If you feel mentally refreshed and are eager to get back to a mentally challenging task after your nap, you are “in the zone” for achieving your goal of using naps to enhance your cognitive performance.

Just as important as getting enough sleep is thinking about sleep in the right way. Stop thinking of sleep and naps as “downtime” or as a “waste of time.” Think of them as opportunities for memory consolidation and enhancing the brain circuits that help skill learning. Nor should you feel guilty about sleep. It’s just as crucial a part of successful brain work as the actual task itself.

PART THREE

Specific Steps for Enhancing Your Brain’s Performance

N
ow that we’ve covered the basics of diet, exercise, and sleep, let’s explore the specific steps you can take to achieve a super-power brain. Some of the world’s most prestigious brain experts have suggested to me that anyone who wishes to develop and maintain an optimally functioning brain must work on the following functions:

Attention:
This must be rock solid. If you can’t maintain focus or concentration, you can’t marshal the effort needed to improve performance in the other brain functions. Attention in the mental sphere is equivalent to physical endurance in the physical sphere.

The Japanese novelist Haruki Murakami—a former couch potato turned marathon runner—captures this link between physical effort and mental concentration, as we have already seen: “Stamina and concentration are two sides of the same coin. I sit at my desk and write every day, no matter whether I like it or not, whether it’s painful or enjoyable. I do this day after day . . . it’s the same as running. You need physical strength for something like that.”

Memory
is a natural extension of attention. If you attend to something you increase your chances of remembering it. Memory also anchors us; in many ways we are the sum total of our memories. We learn from past experiences—but only those that we can remember. As we lose memory, we lose parts of our experience and can suffer a form of identity disorder. But we can combat this by strengthening our memory, by reaching into the past and recapturing earlier thoughts, experiences, and emotions. In the process we unify our personality by integrating our past with our present and our imagined future. In essence, we create who we are.

Traditionally, memory can be broken down into three broad types: sensory memory, long-term memory, and short-term or working memory.

Sensory memory
consists of the brain’s initial recording of physical sensations as they impinge on our sense organs. Iconic memory (things that we see) and echoic memory (things that we hear) are the main forms of sensory memory. Typically sensory memory occurs outside our awareness, but there are ways that we can make the process conscious and thereby improve it.

Long-term memory
refers to information that becomes a permanent part of us (information about our work, our relatives and friends; basic facts about our culture such as holidays, movies, and television shows; income tax deadlines). Long-term memory can be strengthened by practice. You can store as much information as you want in long-term memory over your lifetime without ever exceeding its capacity. Indeed, long-term memory is essentially infinite. Vocabulary is the best example. We can learn new words and phrases throughout our lives, no matter how old we become.

Just because long-term memory is potentially infinite doesn’t mean that you can recall everything that you’ve ever learned. Conversely, forgetting a piece of information doesn’t mean that it has disappeared forever; rather, for one reason or another you cannot retrieve it. Thus people with “good” memories don’t necessarily store more information in their long-term memory—they’re just better at accessing it. As a general rule, memories are best retained and retrieved when they are linked with an image or an emotion.

Working memory:
Also known as short-term memory, working memory involves the most important mental operation carried out by the human brain: storing information briefly and manipulating it. You’re using your working memory whenever you balance two or more competing thoughts, shifting at will from the first thought to the second thought while holding the original thought in a kind of suspended animation. The process is similar to shifting documents on your computer by toggling from one to another.

Working memory differs from long-term memory in an important way. While long-term memory is for the long haul—establishing memories that become permanent and available for future retrieval—working memory is for “right now.” For instance, it was helpful three nights ago for you to temporarily store in your working memory what your waiter looked like so that you could distinguish him from the other waiters in the crowded restaurant when you wished to get his attention. Today you have no need to remember him and, as a result, he is no longer a part of your working memory and occupies an infinitesimal portion of your long-term memory—if you visit that restaurant again you may or may not recognize him.

Think of working memory as the conduit for long-term memory: most things encoded in long-term memory are first processed in working memory. It usually requires concentrated effort by your working memory to encode all of the information now residing in your long-term memory. As a child you learned the alphabet and multiplication tables by laboriously memorizing them, i.e., running them through working memory. Eventually you could recite the alphabet and do the sums automatically as a result of shifting the alphabet and the multiplication tables from working memory into long-term memory. From that point, if you were asked to spell a simple word or carry out a multiplication contained in a table (How much is 7 times 7?), the answer sprang to your lips from long-term memory without the need to first process it using working memory.