|Subject:||MEMORY; BRAIN -- Localization of functions|
|Source:||Newsweek, 06/15/98, Vol. 131 Issue 24, p48, 7p, 14c|
|Author:||Cowley, Geoffrey; Underwood, Anne; et al|
|Abstract:||Examines the function of human memory. Expanding knowledge and understanding of memory, as of 1998; Comparison of the brain's working memory and long-term memory functions to a computer's random-access memory and hard drive; Function of the hippocampus; Variations in personal recall abilities; The impact of stress; Protection of memory. INSETS: Tested your memory lately?; Connections matter; Can supplements boost brain power?|
|Note:||Glendale College Library subscribes to this magazine.|
How Memory Works. . .And What
You Can Do to Improve Yours
Forgetfulness is America's latest health obsession. How much is normal? Can we do anything about it? An explosion of new research offers reassuring insights.
STAN FIELD KNOWS WHAT AGE can do to a person's memory, and he's not taking any chances with his. He chooses his food carefully and gets plenty of vigorous exercise. He also avoids stress, soda pop and cigarette smoke. But that's just for starters. At breakfast each morning, the 69-year-old chemical engineer downs a plateful of pills in the hope of boosting his brainpower. He starts with deprenyl and piracetam--drugs that are normally used to treat diseases like Parkinson's but that casual users can get from overseas sources--and moves on to a series of amino acids (glutamine, phenylalanine, tyrosine). Then he takes several multivitamins, some ginkgo biloba (a plant extract), 1,000 units of vitamin E and, for good measure, a stiff shot of cod-liver oil.
Michelle Arnove is less than half Field's age, but no less concerned about her memory. While working round the clock to finish a degree in film studies, the 33-year-old New Yorker had the alarming sensation that she had stopped retaining anything. ``I couldn't even remember names,'' she says. ``I thought, `Oh no, I'm over 30. It's all downhill from here'.'' Besides loading up on supplements (she favors ginseng, choline and St. John's wort), Arnove signed up for a memory-enhancement course at New York's Mount Sinai Medical Center. And when she got there, she found herself surrounded by people who were just as worried as she was.
For millions of Americans, and especially for baby boomers, the demands of the Information Age are colliding with a sense of waning vigor. ``When boomers were in their 30s and 40s, they launched the fitness boom,'' says Cynthia Green, the psychologist who teaches Mount Sinai's memory class. ``Now we have the mental-fitness boom. Memory is the boomers' new life-crisis issue.'' And, of course, a major marketing opportunity. The demand for books and seminars has never been greater, says Jack Lannom, a Baptist minister and longtime memory trainer whose weekly TV show, ``Mind Unlimited,'' goes out to 33 million homes on the Christian Network. Anxious consumers are rushing to buy do-it-yourself programs like Kevin Trudeau's ``Mega Memory,'' a series of audiotapes that sells for $49.97. And supplement makers are touting everything but sawdust as a brain booster.
But before you get out your checkbook, a few questions are in order. Does everyday forgetfulness signal flagging brain function? Is ``megamemory'' a realistic goal for normal people? And if you could have a perfect memory, would you really want it? Until recently, no one could address those issues with much authority, but our knowledge of memory is exploding. New imaging techniques are revealing how different parts of the brain interact to preserve meaningful experiences. Biologists are decoding the underlying chemical processes--and neuroscientists are discovering how age, stress and other factors can disrupt them. No one is close to finding the secret to flawless recall, but as you'll see, that may be just as well.
To scientists who study the brain, the wonder is that we retain as much as we do. As Harvard psychologist Daniel Schacter observes in his 1996 book, ``Searching for Memory,'' the simple act of meeting a friend for lunch requires a vast store of memory--a compendium of words, sounds and grammatical rules; a record of the friend's appearance and manner; a catalog of restaurants; a mental map to get you to one, and so on.
How do we manage so much information? Brains are different from computers, but the analogy can be helpful. Like the PC on your desk, your mind is equipped with two basic types of memory: ``working memory'' for juggling information in the present moment, and long-term memory for storing it over extended periods. Contrary to popular wisdom, our brains don't record everything that happens to us and then bury it until a hypnotist or a therapist helps us dredge it up. Most of what we perceive hovers briefly in working memory, a mental play space akin to a computer's RAM (or random-access memory), then simply evaporates. Working memory enables you to perform simple calculations in your head or retain phone numbers long enough to dial them. And like RAM, it lets you analyze and invent things without creating a lasting record.
Long-term memory acts more like a hard drive, physically recording past experiences in the brain region known as the cerebral cortex. The cortex, or outer layer of the brain, houses a thicket of 10 billion vinelike nerve cells, which communicate by relaying chemical and electrical impulses. Every time we perceive something--a sight, a sound, an idea--a unique subset of these neurons gets activated. And they don't always return to their original state. Instead, they may strengthen their connections to one another, becoming more densely intertwined. Once that happens, anything that activates the network will bring back the original perception as a memory. ``What we think of as memories are ultimately patterns of connection among nerve cells,'' says Dr. Barry Gordon, head of the memory-disorders clinic at the Johns Hopkins School of Medicine. A newly encoded memory may involve thousands of neurons spanning the entire cortex. If it doesn't get used, it will quickly fade. But if we activate it repeatedly, the pattern of connection gets more and more deeply embedded in our tissue.
We can will things into long-term memory simply by rehearsing them. But the decision to store or discard a piece of information rarely involves any conscious thought. It's usually handled automatically by the hippocampus, a small, two-winged structure nestled deep in the center of the brain. Like the keyboard on your computer, the hippocampus serves as a kind of switching station. As neurons out in the cortex receive sensory information, they relay it to the hippocampus. If the hippocampus responds, the sensory neurons start forming a durable network. But without that act of consent, the experience vanishes forever.
The hippocampal verdict seems to hinge on two questions. First, does the information have any emotional significance? The name of a potential lover is more likely to get a rise out of the hippocampus than that of Warren Harding's Agriculture secretary. Like Saul Steinberg's cartoon map of America (showing the Midwest as a sliver between Manhattan and the West Coast), the brain constructs the world according to its own parochial interests. And it's more attuned to the sensational than the mundane. In a 1994 experiment, researchers at the University of California, Irvine, told volunteers alternate versions of a story, then quizzed them on the details. In one version, a boy and his mom pass a junkyard on their way to visit his father. In the other version, the boy is hit by a car. You can guess which one had more staying power.
The second question the hippocampus asks is whether the information entering the brain relates to things we already know. Unlike a computer, which stores related facts separately, the brain strives constantly to make associations. If you have already devoted a lot of neural circuitry to American political history, the name of Harding's Agriculture secretary may actually hold some interest. And if the hippocampus marks the name for storage, it will lodge easily among the related bits of information already linked together in the cortex. In short, we use the nets woven by past experience to capture new information. And because our backgrounds vary, we often retain very different aspects of similar experiences.
Sophie Calle, a French artist, illustrated the point nicely by removing Magritte's ``The Menaced Assassin'' from its usual place at New York's Museum of Modern Art and asking museum staffers to describe the painting. One respondent (the janitor?) remembered only ``men in dark suits'' and some ``dashes of red blood.'' Another (the conservator?) remembered little about the style or content of the painting but readily described the dimensions of the canvas, the condition of the paint and the quality of the frame. Still another respondent (the curator?) held forth on the painting's film noir atmosphere, describing how each figure in the eerie tableau helps convey a sense of mystery.
By storing only the information we're most likely to use, our brains make the world manageable. As Columbia University neuroscientist Eric Kandel puts it, ``You want to keep the junk of everyday life out of the way so you can focus on what matters.'' Perfect retention may sound like a godsend, but when the hippocampus gets overly permissive, the results can be devastating. Neurologists sometimes encounter people with superhuman memories. These savants can recite colossal strings of facts, words and numbers. But most are incapable of abstract thought. Lacking a filter on their experience, they're powerless to make sense of it.
At the other end of the spectrum stands H.M., a Connecticut factory worker who made medical history in 1953. He was 27 at the time, and suffering from intractable epilepsy. In a desperate bid to stop his seizures, surgeons removed his hippocampus. The operation made his condition manageable without disrupting his existing memories. But H.M. lost the ability to form new ones. To this day, he can't tell you what he had for breakfast, let alone make a new acquaintance. ``Nearly 40 years after his surgery,'' Boston University researchers wrote in 1993, ``H.M. does not know his age or the current date [or] where he is living.''
It doesn't take brain surgery to disrupt the hippocampus. Alzheimer's disease gradually destroys the organ, and the ability to form new memories (sidebar). Normal aging can cause subtle impairments, too. Autopsy studies suggest that our overall brain mass declines by 5 to 10 percent per decade during our 60s and 70s. And imaging tests show that both the hippocampus and the frontal cortex become less active. As you would expect, young people generally outperform the elderly on tests that gauge encoding and retrieval ability.
Fortunately, the differences are minor. Experts now agree that unless you develop a particular condition, such as Alzheimer's or vascular disease, age alone won't ruin your memory. At worst, it will make you a little slower and less precise. ``We continue to encode the general features of our experiences,'' says Schacter, ``but we leave off more details.'' For example, Schacter has found that young adults are usually better than old folks at remembering the details of a picture. But the oldsters quickly catch up when coached to pay more attention. And not everyone needs coaching. Though average scores decline with age, some octogenarians remain sharper and quicker than college kids.
Whatever their age, people vary widely in recall ability. ``Bill Clinton will probably always remember more names than you will,'' says Gordon. ``Unless he has to testify.'' But that's not to say our abilities are completely fixed. Researchers have identified various influences that can keep the brain from working at full capacity. High blood pressure can impair mental function, even if it doesn't cause a stroke. One study found that over a 25-year period, men with hypertension lost twice as much cognitive ability as those with normal blood pressure. Too little sleep (or too many sleeping pills) can disrupt the formation of new memories. So can too much alcohol, or a dysfunctional thyroid gland. Other memory busters include depression, anxiety and a simple lack of stimulation--all of which keep us from paying full attention to our surroundings.
And then there's information overload. ``You used to have time to reflect and think,'' Gordon observes. ``Now you're just a conduit for a constant stream of information.'' It comes at us with terrifying speed--via fax, phone and e-mail, over scores of cable channels, even at the newsstand. And when information bombards us faster than we can assimilate it, we miss out on more than the surplus. As Michelle Arnove (remember her?) discovered, an overwhelmed mind has trouble absorbing anything.
The problem often boils down to stress. Besides leaving us sleepless, distractible and more likely to drink, chronic stress can directly affect our brain chemistry. Like a strong cup of coffee, a stressful experience can energize our brains in the short run. It triggers the release of adrenaline and other glucocorticoid hormones, which boost circulation and unleash the energy stored in our tissues as glucose. The stress response is nicely tailored to the environments we evolved in--where surprise encounters with hungry predators were more common than looming deadlines and gridlocked calendars. But this fight-or-flight mechanism causes harm if it's turned on all the time. After about 30 minutes, says Stanford neuroscientist Robert Sapolsky, stress hormones start to knock out the molecules that transport glucose into the hippocampus--leaving the brain low on energy. And over longer periods, stress hormones can act like so much battery acid, severing connections among neurons and literally shrinking the hippocampus. ``This atrophy is reversible if the stress is short-lived,'' says Bruce McEwen, a neuroscientist at Rockefeller University. ``But stress lasting months or years can kill hippocampal neurons.''
What, then, are the best ways to protect your memory? Obviously, anyone concerned about staying sharp should make a point of sleeping enough and managing stress. And because the brain is at the mercy of the circulatory system, a heart-healthy lifestyle may have cognitive benefits as well. In a 1997 survey of older adults, researchers in Madrid found an association between high mental-test scores and high intake of fruits, vegetables and fiber. An earlier study, conducted at the University of Southern California, found that people in their 70s were less likely to slip mentally during a three-year period if they stayed physically active. Besides protecting our arteries, exercise may boost the body's production of brain-derived nerve growth factor (BDNF), a molecule that helps keep neurons strong.
What about all those seminars and supplements? Can they help, too? The techniques that memory coaches teach can be powerful, but there's nothing magical about them. They work mainly by inspiring us to pay attention, to repeat what's worth remembering and to link what we're trying to remember to things we already know. To remember a new name, says Green of Mount Sinai, listen intently. Then spell it to yourself and make a mental comment about it. Popping vitamins and herbs is easier, but it's no substitute. Preliminary studies suggest that nutritional supplements such as vitamin E and ginkgo biloba may help preserve brain function (chart). But no one has shown convincingly that over-the-counter remedies improve recall in healthy adults.
Estrogen is a different story. While the hormone may not supercharge your memory, it clearly supports brain function. Barbara Sherwin, codirector of the McGill University Menopause Clinic, revealed estrogen's importance two years ago, by testing verbal memory in young women before and after they underwent treatment for uterine tumors. The women's estrogen levels plummeted after 12 weeks of chemotherapy--as did their scores on tests of reading retention. But when half of the women added estrogen to their treatment regimen, their performance promptly rebounded. Researchers at the National Institute on Aging have since found that estrogen may affect visual as well as verbal memory (though not as strongly). And other studies suggest that women who take estrogen may lower their risk of Alzheimer's disease. The reasons are still unclear, but the hormone seems to fuel the development of hippocampal neurons and boost the production of acetylcholine, a chemical that helps brain cells communicate. Unfortunately estrogen has risks as well as benefits, especially for women predisposed to breast cancer. For now, few experts recommend it as a memory aid.
Estrogen is just one of many compounds that pharmaceutical companies are now eying as potential brain savers. ``There are so many drugs under study that I have to believe one or more will make it,'' says James McGaugh, a neuroscientist at the University of California, Irvine. Most are being developed as treatments for Alzheimer's disease, but researchers foresee a day when people will treat even the minor lapses that come with age. ``We want to optimize the opportunity to live a free and independent life,'' says Columbia's Kandel. ``It would be nice to have a little red pill that would take care of it.''
Kandel has formed a company called Memory Pharmaceuticals to exploit his seminal findings about memory. You'll recall that the brain stores information by strengthening the connections among stimulated neurons. To lock in a memory, the neurons in question actually sprout new branches, creating more avenues for the exchange of chemical signals. Kandel has identified a pair of genes--CREB1 and CREB2--that help regulate that process. CREB1 initiates the growth process, while CREB2 holds it in check. Together, they act as a kind of thermostat. Kandel hopes that by selectively inhibiting one gene or the other, we may be able to change the setting on that thermostat. Partially disabling CREB2 might help anyone retain things more easily, without becoming an indiscriminate sponge. And a drug that activated CREB2 (or hogtied CREB1) might help trauma victims avoid having painful experiences seared so vividly into their brains.
It's a thrilling enterprise, but fraught with possible pitfalls. New treatments create new expectations, and not just for the infirm. ``Suppose the drug raises your score on a job test,'' says McGaugh. ``Who gets hired? Does the other guy file suit? Can the employer fire you if you stop taking the drug?'' And suppose parents start feeding the drug to their school-age kids. Others would have to take it just to keep up. Those worries may be vastly premature. Our memory systems have evolved over several million years. If a slight modification made them far more efficient, chances are it would have cropped up naturally by now. The fact is, ``maximal memory'' and ``optimal memory'' are not synonymous, says Cesare Mondadori, chief of research for nervous-system drugs at Hoechst Marion Roussel. As any savant can tell you, forgetting is as important as remembering. So be careful what you wish for.
By Geoffrey Cowley and Anne Underwood
With KAREN SPRINGEN and T. TRENT GEGAX
When it comes to our memories we are our harshest critics, focusing not on countless facts recalled every day, but on the forgotten few. This quiz offers a rough guide to how your memory stacks up against the norm. Now, where did you put that pen?
1 point Not within the last six months
2 points Once or twice in the last six months
3 points About once a month
4 points About once a week
5 points Daily
6 points More than once a day
How often do you fail to recognize places you've been before?
How often do you forget whether you did something, such as lock the door or turn off the lights or the oven?
How often do you forget when something happened--wondering whether it was yesterday or last week?
How often do you forget where you put items like house keys or wallet?
How often do you forget something you were told recently and had to be reminded of it?
How often are you unable to remember a word or name, even though it's "on the tip of your tongue"?
In conversations, how often do you forget what you were just talking about?
Score: 7-14 = better than average memory; 15-25 = average; 26 or higher = below average
ADAPTED FROM: "MEMORY," BY DR. BARRY BORDON AND FROM A. SUNDERLAND, ET AL. (1983 AND 1986).
Our brains aren't designed to retain random bits of information. We remember things by linking them to what we already know. The process is called 'elaborative encoding.'
1 A name is easy to forget when its only point of reference is a face. Lacking links to other memories, it fades within seconds.
2 As you learn facts about a person, such as her profession, her name gets embedded in a web of thoughts and impressions. If you don't know her, random associations have a similar effect.
3 As the web of associations grows, so does the number of paths leading back to the name. Well-encoded memories last a lifetime.
DIAGRAM: Why We Forget/How We Remember
Enthusiasts have embraced a wide range of herbs, vitamins and hormones as mental elixers. Unfortunately, few of them have been shown to sharpen recall in healthy people, and some have dangerous side effects.
Ginkgo Biloba: The most popular purported memory aid comes from the leaves of an ornamental tree. Ginkgo may help increase oxygen flow to the brain, while acting as an antioxidant. One preliminary study suggests it may help relieve mild dementia.
Vitamin E: This antioxidant helps prevent heart disease and boost immune function. Preliminary studies suggest it may also slow the progression of Alzheimer's. But no one has shown it can improve memory in healthy people.
DHEA: After the age of 30, the adrenal glands produce less and less of this hormone. Mice given DHEA supplements excel on learning tasks. It's not clear whether people do.
Aspirin: Regular use of nonsteroidal anti-inflammatories such as aspirin and ibuprofen may delay the onset of Alzheimer's. These drugs can cause gastrointestinal damage, but new versions may not.
Estrogen: Besides lowering the risk of Alzheimer's disease in postmenopausal women, estrogen helps support normal brain function. Studies suggest that estrogen-replacement therapy helps maintain both verbal and visual memory.
DHA: This omega-3 fatty acid, abundant in breast milk, is critical for babies' brain development. No one has shown that it enhances cognition later in life, but supplements are popular.
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Source: Newsweek, 06/15/98, Vol. 131 Issue 24, p48, 7p, 14c.
Item Number: 692891