Controversy #1: Neural Plasticity, Miracle or Banality?
By jtm|June 11th, 2009
Brain plasticity is often touted as a ground-breaking finding in neuroscience, one with important implications for human learning potential, and the malleability of human nature, as seen in psychology. Norman Doidge, author of The Brain That Changes Itself, called it: “one of the most extraordinary discoveries of the twentieth century.”1
Intuitively though, neuroscientists have always known that something must be changing in the adult brain when learning occurs: unfortunately, they just couldn’t find any physical evidence of it for the first half of the twentieth century.The complexity of the human brain, as well as the simpler ones of research animals, eluded them.It was an important affirmation of their premises and hard work then, when starting in the 1960s and 70s, neuroscientists like Eric Kandel found actual changes in neuronal responding due to classical conditioning.The research project to find new forms of functional and structural plasticity of the brain was later greatly accelerated through the 1990s through brain scanning technology, such as magnetic resonance imaging (MRI).Many of the results were fascinating and important milestones for neuroscience.
To get to the controversy, the main problem critics identify with a lot of the recent talk about brain plasticity in psychology is that it glosses over the built-in structure and constraints placed upon the brain by evolution. Steven Pinker, in The Blank Slate: The Modern Denial of Human Nature, devotes a third of a chapter to recent misinterpretations and misuses of neuroplasticity findings.It is easy for neuroscientists and their advocates (sometimes even marketers for miraculous “brain-training” programs and products), to tap into the public’s sense of amazement at the physical nature of the mind.People being natural dualists, are impressed by pronouncements that if one can “Train the Mind” it will “Change the Brain”, according to the title of one bestseller.That’s a good thing too, jokes Pinker, “otherwise we would be permanent amnesiacs”2.The fact that connections between neurons change when we learn only seems fantastic with the foreground assumption of the Ghost in the Machine: the idea that an immaterial mind or soul were being changed instead of the physical brain.Despite being rejected by scientists centuries ago, this folk dualism still plays an important role in our perceptions of the world, so much so that some psychologists have pegged it as a universal aspect of human nature.
Going back to human nature, popularizers of neural plasticity often see it as a defeat of that very idea: the brain having now been shown to be malleable and formable in any way. The blank slate simply becomes the plastic slate, as Pinker observes.But do such conclusions follow from the finding that neurons in the primary sensory cortex can re-organize themselves from experience?Not at all, says Pinker.The first problem is that the kind of plasticity discovered in these sensory areas does not extend to the rest of the brain, or even to the rest of the cortex; the highest level of plasticity yet discovered has often been overgeneralized in popular accounts.And even if it were the case, would it dismiss the idea of an innate human nature?No, because the neurons in any one particular area of the brain continue to do essentially the same thing they had originally been programmed to do by their corresponding genes—the functions they have been shaped for by millions of years of evolution.Even the most extreme examples of cortical plasticity, do not involve radical changes in how neurons within a given brain module function: the auditory cortex continues to act like the auditory cortex, even if processing visual information.
In a seeming contraction to this, a number of children have gone on to live relatively normal lives after the surgical removal of an entire brain hemisphere.In a typical example of the mistakes made within the topic, this discovery channel video (http://www.youtube.com/watch?v=TSu9HGnlMV0) asks rhetorically: “But how could Jodie function normally with one hemisphere?” and then answers:“It’s because of a miraculous ability of the brain called plasticity.”But what the program should have said is “the miraculous characteristic of the brain called bilateral symmetry”; that is, despite some specializations, both halves of the brain have the same structure and perform essentially the same activities.That’s the main reason a human (or any other symmetrical animal) can function nearly normally with half a brain—not plasticity.In contrast, when a brain area that controls a certain function is damaged in both hemispheres, even in very early childhood, that function is lost or damaged permanently.
Nevertheless, because of what’s at stake outside of the scientific arena, there will still be those who imagine that neural plasticity is a miracle discovery that can be used overcome all hard-wired biological limitations, and others like Pinker who manage to keep a cool head and realize that “neural plasticity is just another name for learning and development, described at a different level of analysis”3.In the end, little many have changed in our understanding of the brain as it relates to human behavior.
References:
1: p. XV. Doidge, N. (2007). The Brain That Changes Itself : Stories of Personal Triumph from the Frontiers of Brain Science. New York: Penguin Group. Retrieved from http://en.wikipedia.org/wiki/Neuroplasticity.
2: p. 86.Pinker, S. (2002). The blank slate: The modern denial of human nature. New York: Penguin Books.
Controversy #1: Neural Plasticity, Miracle or Banality?
Brain plasticity is often touted as a ground-breaking finding in neuroscience, one with important implications for human learning potential, and the malleability of human nature, as seen in psychology. Norman Doidge, author of The Brain That Changes Itself, called it: “one of the most extraordinary discoveries of the twentieth century.”1
Intuitively though, neuroscientists have always known that something must be changing in the adult brain when learning occurs: unfortunately, they just couldn’t find any physical evidence of it for the first half of the twentieth century. The complexity of the human brain, as well as the simpler ones of research animals, eluded them. It was an important affirmation of their premises and hard work then, when starting in the 1960s and 70s, neuroscientists like Eric Kandel found actual changes in neuronal responding due to classical conditioning. The research project to find new forms of functional and structural plasticity of the brain was later greatly accelerated through the 1990s through brain scanning technology, such as magnetic resonance imaging (MRI). Many of the results were fascinating and important milestones for neuroscience.
To get to the controversy, the main problem critics identify with a lot of the recent talk about brain plasticity in psychology is that it glosses over the built-in structure and constraints placed upon the brain by evolution. Steven Pinker, in The Blank Slate: The Modern Denial of Human Nature, devotes a third of a chapter to recent misinterpretations and misuses of neuroplasticity findings. It is easy for neuroscientists and their advocates (sometimes even marketers for miraculous “brain-training” programs and products), to tap into the public’s sense of amazement at the physical nature of the mind. People being natural dualists, are impressed by pronouncements that if one can “Train the Mind” it will “Change the Brain”, according to the title of one bestseller. That’s a good thing too, jokes Pinker, “otherwise we would be permanent amnesiacs”2. The fact that connections between neurons change when we learn only seems fantastic with the foreground assumption of the Ghost in the Machine: the idea that an immaterial mind or soul were being changed instead of the physical brain. Despite being rejected by scientists centuries ago, this folk dualism still plays an important role in our perceptions of the world, so much so that some psychologists have pegged it as a universal aspect of human nature.
Going back to human nature, popularizers of neural plasticity often see it as a defeat of that very idea: the brain having now been shown to be malleable and formable in any way. The blank slate simply becomes the plastic slate, as Pinker observes. But do such conclusions follow from the finding that neurons in the primary sensory cortex can re-organize themselves from experience? Not at all, says Pinker. The first problem is that the kind of plasticity discovered in these sensory areas does not extend to the rest of the brain, or even to the rest of the cortex; the highest level of plasticity yet discovered has often been overgeneralized in popular accounts. And even if it were the case, would it dismiss the idea of an innate human nature? No, because the neurons in any one particular area of the brain continue to do essentially the same thing they had originally been programmed to do by their corresponding genes—the functions they have been shaped for by millions of years of evolution. Even the most extreme examples of cortical plasticity, do not involve radical changes in how neurons within a given brain module function: the auditory cortex continues to act like the auditory cortex, even if processing visual information.
In a seeming contraction to this, a number of children have gone on to live relatively normal lives after the surgical removal of an entire brain hemisphere. In a typical example of the mistakes made within the topic, this discovery channel video (http://www.youtube.com/watch?v=TSu9HGnlMV0) asks rhetorically: “But how could Jodie function normally with one hemisphere?” and then answers: “It’s because of a miraculous ability of the brain called plasticity.” But what the program should have said is “the miraculous characteristic of the brain called bilateral symmetry”; that is, despite some specializations, both halves of the brain have the same structure and perform essentially the same activities. That’s the main reason a human (or any other symmetrical animal) can function nearly normally with half a brain—not plasticity. In contrast, when a brain area that controls a certain function is damaged in both hemispheres, even in very early childhood, that function is lost or damaged permanently.
Nevertheless, because of what’s at stake outside of the scientific arena, there will still be those who imagine that neural plasticity is a miracle discovery that can be used overcome all hard-wired biological limitations, and others like Pinker who manage to keep a cool head and realize that “neural plasticity is just another name for learning and development, described at a different level of analysis”3. In the end, little many have changed in our understanding of the brain as it relates to human behavior.
References:
1: p. XV. Doidge, N. (2007). The Brain That Changes Itself : Stories of Personal Triumph from the Frontiers of Brain Science. New York: Penguin Group. Retrieved from http://en.wikipedia.org/wiki/Neuroplasticity.
2: p. 86. Pinker, S. (2002). The blank slate: The modern denial of human nature. New York: Penguin Books.
3: ibid.