Eyes on the Brain

A neurobiologist explores the amazing capacity of the brain to rewire itself at any age

Who's in charge: Me or my neurons?

Who's in charge: me or my neurons?

Recently, I was talking to a friend about the way we think, perceive, and act, and he said, "a person is merely the result of his/her neural circuits." Does that mean that it is our neurons that are in control?

I don't think that people can be summed up by their neural circuits for the simple reason that we, to a large extent, control our own neural circuits. We can make them change.

In the 1990's, scientists at Harvard used brain imaging techniques to show that people can induce significant changes in their brain by the mere act of learning to play a tune on the piano. These experiments were done with adult subjects who had never played the piano or used a keyboard before. After two hours of daily practice for five days, the area of the brain that controls the fingers had expanded considerably. In another study, sighted people were blindfolded day and night and given intensive Braille training. After only five days, their visual cortex, the part of the brain that processes input from the eyes, began to respond to touch.

How can the brain change so dramatically in only five days? This period may not be long enough for new neuronal connections to be made. Instead, the experimental conditions - learning the piano piece or being blindfolded and learning Braille- may have unmasked synaptic connections that are already present but normally ineffective. In all of us, neurons from the touch system may make weak connections with neurons in the visual cortex. When a person is deprived of sight and trained in a difficult tactile task like reading Braille, these connections may be unmasked and strengthened.

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This mechanism may help explain what happened to me when I learned, at age forty-eight to see in 3D. As I describe in my book, Fixing My Gaze, even people like me, cross-eyed since early infancy, are born with a normal binocular visual system. The neurons in my brain initially received input from both eyes. However, I looked through one eye and turned in the other, rapidly switching between the two eyes. Since the two eyes saw different things, they competed for input onto my visual neurons. On each neuron, one or the other eye won out. As a result, I never saw in 3D. Most scientists and physicians thought that this change was permanent, hard wired. But the connection from the weaker eye onto a visual neuron may not have been lost entirely...

At age forty-eight, I underwent vision therapy with a developmental optometrist. Using tools and procedures as simple as they were elegant, I learned to aim both eyes simultaneously at the same point in space. This was something I had never done before and required concentrated, daily practice. But the practice paid off. When I directed my two eyes to the same target, they delivered correlated input to the neurons in my brain. I revived the connections from the weaker eye onto my visual cortical cells so that each neuron was now listening to both eyes. I began to see in 3D. The improvement in my vision was incredible but so was the lesson I learned. By changing my own actions, I changed my visual circuitry. My brain was not so hard-wired after all.

(Note: The Harvard scientists mentioned above include Alvaro Pascual-Leone and his colleagues.
My book, Fixing My Gaze, will be available in bookstores around June 1 and can be pre-ordered from internet book store sites.)

 

Susan R. Barry, Ph.D., is a professor of neurobiology in the Department of Biological Sciences at Mount Holyoke College and the author of Fixing My Gaze (June, 2009).

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