You cut your finger, and after a few days the cut heals. You break a leg, and the bone can be set so that it mends. You work out, and the muscles you exercise become bigger. In many ways, you can see how your body responds to your activities, and even to injury, and somehow reshapes and regenerates itself. When it comes to the brain, however, the idea for a long time was that it was much more fixed in its capabilities than the rest of the body. But we’re discovering that in fact the brain is much more flexible, more plastic, than anyone had known.
Neuroplasticity is the brain’s ability to rewire its connections and reorganize itself, an ability that was once thought to be minimal in adulthood. For one thing, it was long accepted as a truism that if you lost neurons during adulthood, you were out of luck because you were not going to get any more. Adult neurogenesis is a relatively recent and very exciting discovery; your brain goes on producing new neurons well into old age. (One of the more poignant stories of neuroplasticity is the first observation of the growth of new brain cells in adults. Terminal cancer patients were undergoing a treatment that left a biomarker indicating new cell growth. These patients gave permission for their brains to be examined after they died, and the biomarker clearly illuminated the presence of new brain cells.)
The other old idea unseated by discoveries made in the past couple of decades is the idea that different areas of the brain were able to do only a single task and could not be pressed into service for other purposes. It turns out that this is not the case at all. For example, in a blind person the visual cortex is used not only for touch but for processing language (using the sensory input from the fingers that comes through reading braille). Deaf people use their audio cortex for enhanced peripheral vision. People who have had strokes are able, with the right kind of therapy, to regain functions that had been damaged and initially thought lost.
Two new books deal with some of the discoveries and ramifications of neuroplasticity. Doidge centers each chapter of his book on a person or several people who have experienced sometimes dramatic occurrences of a particular type of neuroplasticity, which gives him a readable framework for presenting the neuroscience behind the stories. Begley’s book presents a well-organized progression from discoveries of brain reorganization in animals, through a discussion of brain plasticity in youth, and on to recent research into neuroplasticity in adult brains, including the reshaping of the emotional brainscape that is possible through psychiatric therapy or mental training such as meditation. The books complement each other fairly well (although if I had time to read only one, I’d pick Begley’s, for reasons that I explain below). Of necessity, both cover some of the same stories of discovery, but often from slightly different angles.
The stories of physical problems that can be remedied to one degree or another through engaging the plasticity of the brain are remarkable and often touching. Doidge’s case histories made for easy reading, and it was heartening to read about people who recovered significant functionality after a stroke or other injury, or about children who were able to overcome dyslexia. The sections of both books that dealt with the more straightforward aspects of brain reorganization in response to outside stimuli were among the strongest, in my opinion.
And it’s not just that the brain can reorganize itself to work around damaged areas and regain some functionality. The idea of enhancing brain function in normal people or delaying the consequences of aging is very exciting. I really enjoyed learning about the ways that the brain reacts as a muscle would to repeated demands–not through the same mechanisms, obviously, but frequently used areas of the cortex do grow disproportionately large. E.g., a study of London cab drivers’ brains showed that they tended to have a larger hippocampus–important for navigation–and a study of violinsts’ brains showed that the four fingering digits of the left hand get a disproportionate amount of neural real estate. I am taking to heart Doidge’s advice about learning a new language in old age, as part of a program to keep my brain challenged, active, and I hope functioning well (although it will be a good many years before I need to start thinking about which language it will be).
Neuroplasticity is active not just in the somatosensory cortex (which controls physical sensation and movement) or physical functioning, but also in our emotional states and mental functioning. I tend to think of the new neuroplasticity discoveries in terms of the two areas I described above: adult neurogenesis and brain rearrangement in response to outside events. Scientists used to think these things didn’t happen, and now we know they do and are finding out the degree to which they do. Doidge seems to use the term in a broader sense, talking about learning emotional or behavioral patterns, although obviously the news here is not that it happens but rather that we’re starting to understand better how it happens. He’s a psychiatrist and psychoanalyst, and this is evident in his interest in mental and emotional problems and their treatment. (Most of his stories are enjoyable to read, but if you are at all prone to squeamishness or are apt to be revisited by distressing mental images, spare yourself the section about masochist Bob Flanagan in chapter 4.)
Doidge tries to explain Freudian psychoanalysis in terms of rewiring brain circuits, but I’m not convinced that this really adds anything explanatory, and the case history he chose to illustrate this section was a life of such heartbreaking early losses that it’s hard to apply any of the things he talks about to more everyday emotional problems. His treatment of obsessive-compulsive disorder (OCD) seemed a bit skimpy, which was disappointing. (One of the most striking observations of mental activity changing the brain is Jeffrey Schwartz’s finding that therapy for OCD affected his patients’ brain chemistry; Begley mentioned this in her book, and in fact co-wrote an earlier book with Schwartz that covered the OCD treatments and other aspects of neuroplasticity. I was hoping for a more extensive case history from Doidge on the subject.)
Begley sets her book in the context of the Mind and Life Conference of 2004, a gathering of neuroscientists, philosophers, and Buddhist monks to discuss neuroplasticity. (The Mind and Life series of meetings between the Dalai Lama and western scientists is organized by the Mind & Life Institute.) I felt like her book provided a much broader neuroscience background and also a lot more detail about some of the scientific work, which I really appreciated. (That’s why if I had time to read only one book about neuroplasticity, it would definitely be Begley’s.) And it’s always impressive to see the Dalai Lama’s openness to the findings of science.
The only place in Begley’s book that really bothered me was a chapter that discussed the difficulty of understanding how the mind can change the brain. The Buddhists at the meeting believe that mind is nonphysical and separate from the brain. This is hard to square with Western science, which has found that as far as we can tell, everything we call “mental” is the result of something physical happening in the brain. Western science is still unclear on some of the mechanisms by which conscious mental processes or states change the brain, but it’s a matter of figuring out how one part of a complex system interacts with another. My impression is that what the scientists are grappling with (figuring out how it works) is a far different question from the old Cartesian mind-body interaction, which is what seemed to be exercising the Buddhists, and yet the chapter seemed to me to be implying more common ground than there in fact was.
The bottom line is that I thought both books were informative and worth reading. It’s good to be around to watch brain science teaching us so much about how our brains work and what previously unsuspected capacities they harbor. I hope to hear more in the future about how to make neuroplasticity work for us when it comes to enhancing mental performance and learning new things (that new language I’m going to save for my old age, for example).