by Kenneth W. Krause.
Kenneth W. Krause is a contributing editor and “Science Watch” columnist for the Skeptical Inquirer. Formerly a contributing editor and books columnist for the Humanist, Kenneth contributes regularly to Skeptic as well. He may be contacted at firstname.lastname@example.org.
Brain science has delivered mixed news for lawyers. The bad news is that people become what they think and do. The good news is that even sociopathic ambulance-chasers can rehabilitate themselves simply by thinking about and doing other things. More seriously, the fortunate realities of neuroplasticity and neurogenesis promise considerably more hope than despair for most people, regardless of occupation, age, and medical condition. Armed with an impressive pool of case studies and tales of personal triumph, psychiatrist and Columbia University researcher, Norman Doidge, defies the neurological nihilism of traditionalists who tend to liken the human brain to a predominantly hardwired and localized machine.
Beginning in the 1990s, Harvard researcher Alvaro Pascual-Leone used transcranial magnetic stimulation (TMS) to investigate the neurological means by which people learn new skills. Essentially, TMS allows us to map specific regions of brain activity relative to sensory stimulation. Testing the motor cortices of Braille readers first, Pascual-Leone learned not only that his subjects’ reading finger maps were larger than those corresponding to their non-reading index fingers and to the fingers of non-Braille readers, but also that such maps had expanded during the experiment commensurate to the participants’ growing vocabulary. Importantly, results differed depending on what day of the five-day “work week” the data were collected. That slower but ultimately more permanent changes were recorded on Mondays suggested that the Braille exercises both affected existing neuronal connections and stimulated the formation of new structures.
But Pascual-Leone also wanted to know whether other brain parts, commonly regarded as specialized, could be recruited to the task as well. After using TMS a second time to block signals to his Braille subjects’ visual cortices, Pascual-Leone discovered that they had abruptly lost the ability to read. Interestingly, such blocking had no effect on the visual cortices of sighted people. Apparently, the brains of blind individuals had in some way reorganized themselves to adapt to their unique circumstances. Later, Pascual-Leone blindfolded sighted people. These subjects’ visual cortices began processing tactile and auditory signals in as few as two days. They stopped doing so, however, within only 12 to 24 hours following deprivation. Thus, the doctor concluded, his subjects’ brains hadn’t actually rewired themselves from scratch; they had simply revealed previously hidden but preexisting neuronal pathways. That reorganization occurred so rapidly confirms that brain parts commonly work together and that, in general, they are far from committed or localized.
But can thoughts alone alter material brain structures? Again using TMS, Pascual-Leone studied the finger maps of people learning to play a piano sequence. The members of one group practiced in the traditional way—at the keyboard. Others were restricted to imaginary practice only. In the end, both groups learned to play the sequence and both presented similar brain map changes. Although strictly mental practicers didn’t improve quite as much as the others after five days, they required only a single two-hour physical practice session to catch up. Unrelated PET scans have shown that imaginary images are produced in the same visual centers of the brain as images of external stimuli. Clearly, imagination is an effective means of practical skill acquisition. But these results lend themselves to a much deeper metaphysical issue as well. Cartesian dualists are wrong: Hobbesian materialists are basically right. Minds and brains are not distinct entities. The former, it turns out, are simply occupations of the latter.
And losing half of one’s brain can result in losing half of one’s mind, more or less. But perhaps not the half you might think if you subscribe to the traditional view of laterality. The left hemisphere, by this theory, is the immutable verbal domain where symbols and calculations are managed. The right brain, by contrast, handles visual-spatial activities, including those requiring more abstract or imaginative thought. But laterality alone, responds Jordan Grafman, neuroscientist at the National Institutes of Health, cannot explain the condition of “Paul,” for example, whose right parietal lobe was seriously damaged when he was seven months old. Surprisingly, an older, teenaged Paul had difficulty processing numbers—a normally left-brained enterprise. A functional MRI scan revealed the very faint activation of Paul’s left parietal area during a simple math exercise, so the problem was obviously not that the boy’s lobe had failed. Nor can mere laterality explain “Michelle,” who because of a developmental anomaly was born with half of a brain—the right half. At 25, Michelle has an exceptional memory, but was very weak with a variety of abstractions. Rote memorization, however, is a typically left-prefrontal occupation, and, still possessing an intact right hemisphere, one might presume Michelle to be rather more adept with themes and concepts.
According to Grafman, only plasticity—or more specifically “mirror region takeover”—can account for these enigmas. When a portion of one hemisphere fails, its mirror region adapts to the relevant tasks as well as it can. No doubt age was an important factor in these two cases. At seven months, Paul’s left parietal lobe never had a chance to commit itself to typically left-brained skills like calculation, and, because visual-spatial acuities are absolutely crucial for young children, Paul’s left parietal region promptly donated itself instead to typically right-brained functions. With Michelle, the same occurred in reverse. Still in her mother’s womb, Michelle’s right prefrontal area had no opportunity to commit itself to abstrusion. At such a tender age, recognizing speech and collecting memories would have been infinitely more important. While Grafman concedes that brain hemispheres and sectors tend to specialize by certain junctures prior to adulthood, his research clearly demonstrates that they are anything but hardwired to do so.
And even old lawyers can learn new tricks, as it turns out. In fact, they can do much better than that when sufficiently motivated. The prescribed regimen, however, is both varied and intense. Because minds represent the labors of brains, we shouldn’t be surprised that they rely on efficient oxygenation. But energetic and consistent physical exercise promotes plasticity as well by stimulating the production and release of neuronal growth factor BDNF. Intellectual vigor, however, is at least equally critical. Touted as the world’s leading researcher on brain plasticity, Michael Merzenich estimates that every 85 year-old faces a 47 percent chance of having Alzheimer’s disease, largely as a result of cognitive neglect. In order to maintain the areas of our brains that control and regulate plastic change, we of middle age or better must consistently invest our minds in novel and absorbing pursuits—much as a developing child would by necessity. To that end, Merzenich launched Posit Science, a company that published its first control study in the 2006 Proceedings of the National Academy of Sciences, USA. After only 40 to 50 hours of auditory memory exercise, subjects between the ages of 60 and 87 not only performed better, but also showed increased metabolic activity in a number of sectors including the right parietal lobe. The control group, by contrast, presented signs of metabolic decline typical to their age group. Posit Science is also developing programs to enhance motor control, visual processing, and frontal lobe executive function.
But pernicious changes can occur as well, and often do. Early childhood traumas and depression or stress in adults cause the release of glucocorticoid hormones that kill hippocampal cells responsible for the retention of long-term explicit (conscious) memories. In some cases, the organ’s dimensions have shrunk by 18 percent. When the depression is temporary, native stem cells can rescue the hippocampus. But if it lasts, the damage will be permanent. More generally, however, any unvaried and repetitious endeavor can result in what Doidge calls the “plastic paradox.” Despite common assumptions about supposedly rigorous careers and elevated cultural habits, the dark side of plasticity can eventually doom otherwise active and healthy adults to bland, rigid, and neurotic existences. Use it, as the expression goes, or lose it.