Learning To Change

A User's Guide to the Brain: Perception, Attention, and the Four Theaters of the Brain
by John J. Ratey, M.D.

(Page 8 of 12)

The neural pathways that control the basic functions we need to survive-heartbeat, temperature control, breathing-are already connected at birth, but many more pathways are determined by the greatest environmental factor in our lives: learning. Although the brain's flexibility may decrease with age, it remains plastic throughout life, restructuring itself according to what it learns.

The brains of children three to ten years old consume twice as much of the blood nutrient glucose as those of adults, in part because their brains are less efficient and are in the business of forming a vast number of connections. Studies also show that children who exercise regularly do better in school. New research indicates that adult exercise juices the brain with more glucose too, which may promote an increase in neural connections.

Because the young brain prunes weak connections, environmental input in a child's early years can have amazing or devastating effects on the brain's wiring, and thus on future behavior. Geraldine Dawson at the University of Washington followed 160 children from infancy until age six. She found that infants raised by depressed mothers-and so not exposed to many smiles or sounds of excitement in response to their actions-showed reduced activity in the left frontal region of the brain, the area responsible for the expression of positive emotions. At three and a half years of age, the children were more likely to exhibit behavioral problems. In cases such as these, intervention by positive fathers or other caregivers and having the mothers undergo treatment could help to strengthen the neural connections before they are eliminated permanently.

Neurons are constantly competing to make connections. Many maps have been drawn that match each region of the brain to the function it controls: one area for speech, another for spatial skills, and so on. However, changes in environmental input continually move the boundaries. An accurate map of the brain would be different for each of us, and would shift over time. Connections that receive input from frequently used body parts will expand and take up more area than those that receive input from infrequently used parts. Magnetic resonance imaging (MRI) shows that the brains of violin players devote much more area to pathways representing the thumb and fifth finger of the left hand-the fingering digits-which are used extensively in hours of training. The younger a child begins practicing, the more area her cortex devotes to these fingers.

The competition to gain more representation in the brain explains why babies born with cataracts that cloud their vision must have them removed by six months or never gain sight. The brain must learn to see, making connections and stimulating them with inputs from the retina. If these pathways aren't stimulated, they will be eliminated as not useful. Many of us who need glasses have a different prescription for each eye to make the eyes comparably strong. Otherwise, neurons serving the stronger eye will branch out their connections, beating out the neurons serving the weaker eye and making the latter permanently weak. This condition is known as amblyopia. To stimulate the neurons of a weaker eye and prevent its becoming amblyopic, eye doctors will patch the stronger eye. If one eye of a newborn kitten is sewn closed, the eye's neural connections will wither and disappear from lack of use. If the eye is later opened it will never gain sight, because the stronger eye has permanently taken over the available synapses, and, more important, the weaker eye has permanently lost its ability to make connections.

Changing your pattern of thinking also changes the brain's structure. Jeffrey Schwartz at the University of California at Los Angeles School of Medicine found that obsessive-compulsive patients who changed their problematic behavior by repeatedly not giving in to an urge, and deliberately engaging in another activity instead, showed a decrease in brain activity associated with the original, troublesome impulse. It is theorized that neurons contain tiny electromagnetic fields that become misaligned, or "locked," for the duration of a disease or disorder. The neurons get stuck in a rut of abnormal patterns of activity, becoming underactive or overactive or just nonperforming, it being either too easy or too hard for them to fire. A person who forcibly changes his behavior can break the deadlock by requiring neurons to change connections to enact the new behavior. Changing the brain's firing patterns through repeated thought and action is also what is responsible for the initiation of self-choice, freedom, will, and discipline. The drug Prozac can be helpful in breaking these kinds of deadlocks.

We always have the ability to remodel our brains. To change the wiring in one skill, you must engage in some activity that is unfamiliar, novel to you but related to that skill, because simply repeating the same activity only maintains already established connections. To bolster his creative circuitry, Albert Einstein played the violin. Winston Churchill painted landscapes. You can try puzzles to strengthen connections involved with spatial skills, writing to boost the language area, or debating to help your reasoning networks. Interacting with other intelligent and interesting people is one of the best ways to keep expanding your networks-in the brain and in society. Some of these activities help owing to a neurological phenomenon called cross-modal influences-cross-training in the sports world. For certain sets of skills, training one part of the brain also benefits another. As we will see in the discussion of language in Chapter 7, dyslexic children who repeatedly listen to elongated sounds generated by a computer can improve their ability to spell and read. A study performed by a team at the University of California showed that college students who listened to 10 minutes of Mozart's piano sonatas just prior to taking spatial reasoning tests scored higher than students who listened to relaxation tapes or the more hypnotic music of Philip Glass. This "Mozart effect" lasted only 15 minutes, though, and other studies have shown weaker improvement or none at all. More research is needed before we all start strapping Sony Walkmans to our heads or sending Mozart tapes home with newborn babies.

There is stronger evidence, however, that children who listen to and play music at ages younger than eight do better on spatial reasoning tests. For example, the California team studied a class of three-year-olds. Half the class attended piano or singing lessons for eight months. Their scores on puzzles, tests of spatial reasoning, and drawing of geometric figures shot up to 80 percent higher than those of their classmates who did not attend music lessons. The musical children gradually became faster and more accurate at spatial reasoning over the school year and boosted their spatial intelligence. The theory is that as music is structured in space and time, practicing it will strengthen circuits that help the brain think and reason in space and time, important for math. If the effect of sustained practice during childhood is permanent, the improved ability will help children in complex math and engineering problems when they grow up. It is theorized that the music triggers neural firing patterns over large regions of the cortex that are also used for spatial reasoning.

Activities that challenge your brain actually expand the number and strength of neural connections devoted to the skill. But as Merzenich's monkeys showed, when complex motor tasks become routine they are pushed down to the subcortical areas, where they reside as more automatic programs. Once a procedure is stored in this lower memory it becomes hard-wired. That's why we can get on the proverbial bike and pedal away after a decade of not riding. If these skills had stayed in the higher cortex and been unused, the connections would have withered and been lost. Adults who gave up their rock-'n'-roll bands in high school find that when they pick up a guitar years later they can still play, and when their children bring home their first algebra problems, they can still set up an algebraic equation.

The more that higher skills such as bike-riding and cognition are practiced, the more automatic they become. When first established, these routines require mental strain and stretching-the formation of new and different synapses and connections to neural assemblies. But once the routine is mastered, the mental processing becomes easier. Neurons initially recruited for the learning process are freed to go to other assignments. This is the fundamental nature of learning in the brain.

The brain's ability to rewire means that in principle it can recover from damage. Young children who have had an entire brain hemisphere removed because of severe epilepsy manage to compensate with only slight mental or physical disabilities. Intense physical and mental rehabilitation allows circuits in the remaining hemisphere to gradually rewire, taking over many of the functions that the lost hemisphere used to perform. Things won't ever be "normal," as the original well-trained and appropriately placed circuits have been lost, but even complex functions such as language and reasoning are relatively spared after this sudden, massive loss of neurons. We will encounter several examples of such dramatic rewiring throughout this book.

The brain is amazingly plastic. In the past it was commonly accepted that any brain damage was permanent; once a brain region died, the function it controlled was gone forever. More than 500,000 Americans have strokes each year, killing many neurons and cutting many connections, yet in many of them undamaged neurons take over, changing the number, variety, and strength of the messages they send, rerouting traffic around the accident site. Rewiring is possible throughout life.

New connections take time to form and strengthen. They gradually learn what is most useful and adapt. Many stroke victims lose language abilities, but neighboring circuits or neurons in the nondamaged hemisphere try to take over and compensate for the lost function. Of course, these patients are relying on different neural connections that are probably less efficient for language, so their speech may never be as natural or easy. In cases where brain damage occurs slowly, such as Alzheimer's disease, the brain has more time to compensate, and many deleterious effects can be postponed, though the progressive march of this devastating disease cannot yet be stopped.

The brain reacts differently to injury during different periods of development. Prenatal or early childhood brain damage is often less problematic since many neural circuits are not yet committed to specific skills, knowledge, or memories. The brain can readily rewire on a widespread scale. Although the damage may result in a smaller adult brain or one of lesser overall intellectual abilities, it will seldom cause specific deficits. Most lasting problems are actually due to misconnections from neurons that try to branch out and fill new roles. In later childhood, major damage will be more permanent, although many skills can still be recovered. Plasticity at multiple levels is more active in early life, so that damage at one site produces changes at many other sites, thus changing the brain and its functioning in a more widespread manner. In later life, with less capacity for remodeling at multiple levels, effects at a distance from the site of damage are less likely and specific deficits are more common. From mid-adolescence on, there is less rapid growth of new synapses that allow for flexibility, and by then neurons are completely myelinated, or sheathed. Damage will cause deficits in specific skills with varying degrees of recovery. The more we learn about how the brain restructures itself, the better we will be able to direct other brain areas to take over faulty functions, resulting in greater recovery from trauma and disease.

Excerpted from A User's Guide to the Brain by John J. Ratey, M.D. Copyright © 2002 by John J. Ratey, M.D.. Excerpted by permission of Vintage, a division of Random House, Inc. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.

About the Author

John J. Ratey, M.D., is an associate professor of psychiatry at Harvard Medical School. He has lectured extensively and published many articles on the topic of treating adults with ADD. Dr. Ratey is the author of A User's Guide to the Brain and the co-author of Driven to Distraction. He lives in Cambridge, Massachusetts, where he has a private practice.