The Brain That Changes Itself: Stories of Personal Triumph from the Frontiers of Brain Science

by Norman Doidge

felt. It seemed possible that acupuncture turns on neurons that inhibit pain, closing gates and blocking pain perception.

“Pain is an opinion on the organism’s state of health rather than a mere reflexive response to injury.”

When Pascual-Leone used TMS to map the motor cortex, he found that the maps for people’s “Braille reading fingers” were larger than the maps for their other index fingers and also those for the index fingers of non-Braille readers. Pascual-Leone also found that the motor maps increased in size as the subjects increased the number of words per minute they could read. But his most surprising discovery, one with major implications for learning any skill, was the way the plastic change occurred over the course of each week.

mental practice is an effective way to prepare for learning a physical skill with minimal physical practice.

subjects who had done physical exercise increased their muscular strength by 30 percent, as one might expect. Those who only imagined doing the exercise, for the same period, increased their muscle strength by 22 percent. The explanation lies in the motor neurons of the brain that “program” movements. During these imaginary contractions, the neurons responsible for stringing together sequences of instructions for movements are activated and strengthened, resulting in increased strength when the muscles are contracted.

The goal in these approaches is ultimately to implant a small microelectrode array, with batteries and a transmitter the size of a baby’s fingernail, in the motor cortex. A small computer could be connected either to a robotic arm or wirelessly to a wheelchair control or to electrodes implanted in muscles to trigger movements. Some scientists hope to develop a technology less invasive than microelectrodes to detect neuronal firing— possibly a variant of TMS, or a device Taub and colleagues are developing to detect changes in brain waves.

What it implies is that people learning a new skill can recruit operators devoted to other activities, vastly increasing their processing power, provided they can create a roadblock between the operator they need and its usual function.

Each thought alters the physical state of your brain synapses at a microscopic level.

As Freud discovered, recurring dreams, with a relatively unchanging structure, often contain memory fragments of early traumas.

Depression, high stress, and childhood trauma all release glucocorticoids and kill cells in the hippocampus, leading to memory loss. The longer people are depressed, the smaller their hippocampus gets.

If the stress is brief, this decrease in size is temporary. If it is too prolonged, the damage is permanent.

Antidepressant medications increase the number of stem cells that become new neurons in the hippocampus. Rats given Prozac for three weeks had a 70 percent increase in the number of cells in their hippocampi. It usually takes three to six weeks for antidepressants to work in humans—perhaps coincidentally, the same amount of time it takes for newly born neurons in the hippocampus to mature, extend their projections, and connect with other neurons.

“If we lived in this room only,” he told me, “and this was our entire experience, we would not need neurogenesis. We would know everything about this environment and could function with all the basic knowledge we have.” This theory, that novel environments may trigger neurogenesis, is consistent with Merzenich’s discovery that in order to keep the brain fit, we must learn something new, rather than simply replaying already-mastered skills.

The more education we have, the more socially and physically active we are, and the more we participate in mentally stimulating activities, the less likely we are to get Alzheimer’s disease or dementia. Not all activities are equal in this regard. Those that involve genuine concentration—studying a musical instrument, playing board games, reading, and dancing—are associated with a lower risk for dementia. Dancing, which requires learning new moves, is both physically and mentally challenging and requires much concentration. Less intense activities, such as bowling, babysitting, and golfing, are not associated with a reduced incidence of Alzheimer’s.

The most we can say about the relationship between brain exercises and Alzheimer’s at the moment is that it seems very promising.

Physical activity is helpful not only because it creates new neurons but because the mind is based in the brain, and the brain needs oxygen. Walking, cycling, or cardiovascular exercise strengthens the heart and the blood vessels that supply the brain and helps people who engage in these activities feel mentally sharper—

Recent research shows that exercise stimulates the production and release of the neuronal growth factor BDNF, which, as we saw in chapter 3, “Redesigning the Brain,” plays a crucial role in effecting plastic change. In fact, whatever keeps the heart and blood vessels fit invigorates the brain, including a healthy diet. A brutal workout is not necessary—consistent natural movement of the limbs will do. As van Praag and Gage discovered, simply walking, at a good pace, stimulates the growth of new neurons.

plasticity. The first is “map expansion,” described above, which occurs largely at the boundaries between brain areas as a result of daily activity. The second is “sensory reassignment,” which occurs when one sense is blocked, as in the blind. When the visual cortex is deprived of its normal inputs, it can receive new inputs from another sense, such as touch. The third is “compensatory masquerade,” which takes advantage of the fact that there’s more than one way for your brain to approach a task. Some people use visual landmarks to get from place to place. Others with “a good sense of direction” have a strong spatial sense, so if they lose their spatial sense in a brain injury, they can fall back on landmarks. Until neuroplasticity was recognized, compensatory masquerade—also called compensation or “alternative strategies” such as switching people with reading problems to audio tapes— was the chief method used to help children with learning disabilities. The fourth kind of plasticity is “mirror region takeover.” When part of one hemisphere fails, the mirror region in the opposite hemisphere adapts, taking over its mental function as best it can.

We share 98 percent of our DNA with chimpanzees. The human genome project enabled scientists to determine precisely which genes differed, and it turns out that one of them is a gene that determines how many neurons we will make.