Border Disputes

God, grant me the serenity

To accept the things I cannot change

Courage to change things I can

And wisdom to know the difference.

THE SERENITY PRAYER has been adopted by Alcoholics Anonymous and other organizations that help members recover from addiction. It reveals why the brain fascinates people so much: They are always hoping to change it. Just stroll through the self-help section of your local bookstore -- you'll see hundreds of titles on how to drink less, quit drugs, eat right, manage money, discipline your kids, and save your marriage. All these things seem possible, but they are difficult to achieve.

Certainly normal, healthy adults would like to change their behaviors, but this goal is even more critical for those with mental disabilities and disorders. Can a young adult ever be cured of schizophrenia? Can a grandparent learn to speak again after a stroke? And we all want our schools and our childrearing to mold young minds for the better. Can we improve the way this is done?

The Serenity Prayer asks for courage and widom about change. Wouldn't it be better to have answers from neuroscience as well? After all, changing the mind is ultimately about changing the brain. But neuroscience can never aid the quest for self-improvement without answering a more fundamental question: How exactly does the brain change when we learn to behave in a new way?

Parents marvel at the speed of their babies' development, excitedly celebrating every new action or word as a wondrous occasion. The infant brain grows rapidly, reaching close to adult size by two years of age. This suggests a simple theory: Perhaps learning is nothing more than brain growth, and children can be made smarter by enhancing this growth.

This theory goes back yet again to the phrenologists. Johann Spurzheim argued that mental exercise could enlarge cortical organs, much as muscles build up after physical training. Based on this theory, Spurzheim went on to develop an entire philosophy of education for both children and adults.

More than a century passed before his theory was finally tested scientifically. By that time, psychologists had invented a way of studying the effects of stimulation on the animal mind. Laboratory rats were placed in two different environments, one dull and the other "enriched." In the dull cage, a solitary rat lived with food and water containers as the only decoration. In the enriched cage, many rats lived to gether in a group and were provided daily with new toys. By running the rats through simple mazez, researchers found that the enriched rats were smarter. Presumably their brains were different, but exactly how?

In the 1960s Mark Rosenzweig and his colleagues decided to find out. Their method was startlingly simple: They weighed the cortex. It turned out that the enriched cage slightly enlarged the cortex on average. This was the first demonstration that experience causes the brain's structure to change.

You might not be surprised. After all, what about those MRI studies showing that London taxi drivers, musicians, and bilinguals have enlarged brain regions? Once again we must be careful not to read too much into statistical findings. The MRI studies showed correlation, but they did not prove causation.

Did driving a taxi, playing a musical instrument, and speaking a second language cause the brain to enlarge, as in Spurzheim's theory? Causation could be claimed if the brains of musicians and non-musicians were the same before musical training, and only became different afterward. But since the MRI study only collected data about "after", it cannot rule out an alternate interpretation: Perhaps some people are born with a brain enlargement that endows musical talent, and these gifted people are more likely to become musicians. Enlarged brains cause musical training, not the other way around.

Musicians may be selected on the basis of innate talent by music teachers and competitions. And musicians may be self-selecting, since people generally prefer activities at which they excel. This sort of problem, known as selection bias, complicates the interpretation of many statistical studies. Rosenzweig eliminated selection bias by radomly installing some rats in the enriched cage and others in the dull cage. This ensured that the two groups of rats started out statistically identical, enabling him to interpret any differences after the cage experience as having been caused by it.

For an even more direct demonstration of causation, one can use MRI to compare human brains before and after anexperience. In this way, researchers found that learning to juggle balls thickened the cortex in the parietal and temporal lobes. And intensive study for exams caused the parietal cortex and the hippocampus to enlarge in medical students.

These results are impressive, but they are still not what we want. It is not enough to show that experience changes the brain. We also want to know whether the change is the cause of the improved performance. To understand why proof is still lacking, consider the following analogy. Imagine that musical training causes musicians to become more obese by forcing a sedentary lifestyle of practicing all day long. It would be wrong to conclude that obesity causes their improved musical performance. Similarly, showing that musical training enlarges the brains of musicians does not prove that this growth causes them to play their instruments better.

Rosenzweig showed that living in the enriched cage made rats smarter and also thickened their cortex. He did not prove, however, that it was the thickening that caused the improvement in intelligence. In fact, this seems unlikely, given what we know about the funtion of cortical regions. The frontal lobe is thought to be important for skills like maze-running, but it showed little or no increase in size. The occipital lobe, which is responsible for visual perception, showed the largest increase.

In the end, we cannot equate cortical thickening with learning. We can say only that these two phenomena are correlated. Furthermore, the correlation is weak, once again revealed only by averages over groups. Cortical thickening is not a reliable predictor of learning in individuals.

Perhaps studying maze-running or juggling is the wrong approach. Maybe we should study more dramatic changes. Immediately after a stroke, for example, a patient usually experiences wekness or paralysis and may also lose speech and other mental abilities. Many patients improve dramativally over the nex few months. What happens to the brain during recovery? Research on this question is of clear practical importance, as it could help us develop better therapies. Srokes are caused by blocked or leaking blood vessels that damage the brain. The symptoms often indicate which side of the brain has been damaged. If patients struggle to control one side of the body, as is frequently the case, it means that the opposite side of the brain has been damaged, because each side of the brain controls muscles on the opposite side of the body. Neurologists can sometimes further pinpoint the affected brain region. To describe the location of cortical injury, a neurologist may specify a lobe or, if more precision is needed, a particular fold in a lobe. The folds have fancy-sounding names like "superior temporal gyrus," which means the uppermost fold in the temporal lobe. Alternatively, a cortical area may be specified by a number rather than a name, using a map published by the German neuroanatomist Korbininian Brodmann in 1909 (see Figure 11). In this book I will use the term area to mean a subdivision of Broadmann's map, and region to refer to any subdivisions of the brain.

-- Page 22-26 Part I DOES SIZE MATTER? TWO: Border Disputes, CONNECTOME: How The Brain's Wiring Makes Us Who We Are, Sebasitan Seung