Neuroplasticity and why it matters
Murray’s view that IQ and therefore academic ability is largely hardwired by the genes and set within quite narrow limits by the ages of 6-10 is also challenged by a recent Copernican revolution in the brain sciences, which has found that the brain is plastic and changes itself in response to experience throughout life.
One of the principal supports of pessimistic views like Murray’s has been the alternative and earlier view that the brain is fixed and set at a very early age. For nearly four hundred years, the settled opinion of neuroscientists was that neurons cannot rejuvenate themselves. On that earlier view, after neurons develop—mostly in the womb and in infancy and early childhood under the direction of genes—they can only die.
Beginning in the 1960s and 1970s, work by maverick neuroscientists began to challenge this view. Important evidence started to emerge from the laboratories that the brain changes itself throughout life in response to the person’s experiences—a phenomenon now dubbed neuroplasticity. The findings rapidly accumulated, and led in the 1990s to a revolution in the brain sciences. The view that the brain is plastic is now the mainstream view, and further evidence of the phenomenon is accumulating rapidly—and almost on a daily basis.
Neuroplasticity is directly relevant to many of the issues addressed by Murray in Real Education. The view that the brain is fixed and non-plastic after adolescence has buttressed skepticism that academic abilities can be trained and developed, and therefore that learning transfer can take place. Many of the founders of the field of educational psychology like Edward L. Thorndike, who were deeply involved in the intelligence testing movement in the early part of the 20th century, accepted this view. Like Murray, most of these early educational psychologists scouted the idea that academic ability could be developed, because for them it was hardwired and largely determined by the genes.
Before the 1990s, and certainly before the 1970s, educational psychologists could plausibly argue that the universally held view of neuroscientists that the brain is non-plastic strongly supported their skepticism about the possibility of developing cognitive and academic skills. Such skepticism is no longer supported by the neurosciences. To be sure, the new view of the neuroplastic brain does not prove that views like those of Thorndike and Murray are wrong. The findings do not yet force the conclusion that their views must be rejected. But they do challenge one of the crucial props for their skepticism. As I will argue shortly, neuroplasticity also provides a ready explanation for some findings about human intelligence that the views of people like Thorndike and Murray cannot provide.
The ideal introduction to the neuroplastic revolution in brain science is the best-seller The Brain that Changes Itself by Norman Doidge. Murray refers to neuroplasticity and to the Doidge book in Real Education, but his very brief references to it, it seems to me, fail to do justice to the issues that neuroplasticity raises for education.
Murray’s reference to Doidge (which occurs in a footnote) and to neuroplasticity comes in one of the beginning sections of the book. That section is devoted to arguing that there is very little that we can do to change underlying academic ability—or as he puts it, “in terms of tests, our capacity to raise IQ scores.” Murray does, however, introduce some caveats, the main purpose of which is to allow that things outside the schools might be able to improve academic ability and IQ scores. He believes, though, that the schools themselves can do little or nothing to do so.
He concedes that genes “are not even close to being everything,” and that environment—except, apparently, the school environment—is very important. Some of the environmental variables affecting IQ that he believes are important include the family environment (shown in adoption studies), poverty, and high stress during infancy and early childhood. It is in this context that he mentions neuroplasticity. Here the text says (a footnote to it refers to the Doidge book, which Murray calls “entertaining”):
Furthermore, important evidence has been found for the plasticity of certain mental processes, especially during infancy and early childhood. We have reason to hope that, sometime in the future, technologies for early intervention that produce dramatic and permanent change will be developed. For that matter, the future will bring technologies for manipulating genes that achieve the same end.
To begin to grasp the possibilities for education at all levels raised by neuroplasticity, consider the following findings that Doidge mentions in his book. Though I do not give the references here, all the findings in Doidge’s book are fully documented with references to the research literature:
- Eric Kandel, by studying the unusually large neurons of a species of sea snails, produced the first laboratory finding that learning and experience actually change the structure of neurons. Further research on all organisms (including humans) with a sufficiently complicated neural structure has shown that neurons have the power to generate proteins that autoregulate and change the neuron’s structure throughout life. Kandel found that when a single neuron develops long term memory for an event to which it has become sensitized, it might go from having 1,300 to 2,700 synaptic connections—a huge amount of neuroplastic change. Brain research has identified a growth factor, called BDNF, that helps consolidate connections between neurons and wire them together.
- Before the neuroplastic revolution, neuroscientists believed that in the adult brain everything may die, but nothing may be regenerated. We now know that this is not true. Neuronal stem cells have the capacity to go on dividing and replicating themselves endlessly, without any sign of aging. This rejuvenating process is called neurogenesis. Neurogenesis goes on until the day we die.
- One important way that the brain changes and remaps itself in response to experience is by increasing or decreasing the number of synaptic connections between neurons. The number of these connections is unimaginable. The human brain contains approximately 100 billion neurons. The number of possible synaptic connections and neural circuits involved in the connections between and among these 100 billion neurons makes the human brain by far the most complicated entity in the known universe. Gerald Edelman has calculated that the number of possible neural circuits in the brain is 10 followed by a million zeros. This should be compared with the number 10 followed by 79 zeros, which is the estimate of the total number of particles in the universe.
- When entire areas of the brain are adversely affected, other parts can take over, thereby overthrowing the one location, one function theory of the brain, according to which genes and very early development result in a brain map that is fixed for life. For example, the visual cortex can take over, at least partially, the functions of the part of the cortex that responds to touch. Furthermore, cerebral reorganization of this kind is not limited to certain sectors or lobes of the brain. If one brain system changes, those connected to it change as well. (Some of the weirdest case studies in Doidge’s book concern this phenomenon).
After neuroplasticity-based therapy, the size of the affected parts of the brain has been found to double.
- Changes in functions show up not just behaviorally, but also in brain scans like fMRIs, PET scans, CT scans, and surgical procedures involving microelectrodes.
- Neuroplasticity involves the higher cognitive functions as well as memory and motor and sensory functions. No part of the brain is an exception. IQs of retarded individuals have been raised. Even thought and imagination, as brain scan technologies have clearly demonstrated, can change the structure of our brains.
Mental training or life in enriched environments increase brain weight by 5 percent in the cerebral cortex of animals and up to 9 percent in the areas that the training directly stimulates. Trained or stimulated neurons develop 25 percent more branches and increase their size, the number of connections per neuron, and their blood supply. Rats in enriched environments have been found to have 40 thousand more neurons than the control group after they have been sacrificed and dissected. The numbers are even higher for older mice. Older rats in the enriched environments have a fivefold increase in the neurons in the hippocampus, and demonstrated greater gains in tests of learning, exploration, movement, and other measures of mouse intelligence than those raised in unenriched conditions.
- In general, all brain functions, including the higher cognitive functions, are now seen to be developed by a rich and complex interplay of the brain with its experience and environment. In response to experience, the brain grows new neurons, changes and multiplies the synapses (connectors between neurons), and reorganizes the neural circuitry of the brain. It is true that this occurs more rapidly and massively in fetuses, neonates, and early childhood, but it is very much an ongoing process. It goes on all the time, involving all parts of the brain and all brain functions (including cognition), as part of our normal response to experience, and not just in response to major trauma.
Appendix 1 of the Doidge book, on “The culturally modified brain,” discusses the views of Marshall McLuhan and others that the new technologies and media of the Information Age are massively changing our sensory and cognitive functions. (Unfortunately, this is not always for the better). One of the leading neuroplastic researchers covered by Doidge, Michael Merzenich, has also concluded that neuroplasticity makes it likely that our brains are actually quite different from those of all generations before us. Merzenich’s claim is likely to be relevant to an important and very puzzling finding from research on human intelligence called the Flynn Effect.
Image: Wikimedia Commons, Public Domain