… was with us at the IPK on tuesday night. Here is the essay she wrote for the panel "What Does the Brain Do?"
Born severely cross-eyed, Barry takes us on her journey toward binocular vision. Beyond the physical change from turning her head to suppress the vision of one eye at a time, she explains the experiential shift and emotional change of seeing in three dimensions.
Photo credit: Keke Keukelaar
One common approach to studying the brain is to examine the consequences of brain injuries. If an individual suffers a stroke, for example, and loses the ability to speak, then the damaged area of the brain may play a role in language. A second, perhaps less common, strategy is to study the process of rehabilitation following a brain injury or disorder. As I will illustrate in this talk, the type of therapy and amount of practice involved in successful recovery provides insights into the fundamental functions of the brain.
For the past century, conventional wisdom held that the adult human brain is largely immutable. Most of its circuitry is laid down by early childhood with little possibility for rewiring in adulthood. Great emphasis has been placed on the role of “critical periods” in early life for the development of basic perceptual and language skills. Once these critical periods were passed, little neuronal reorganization was thought possible.
For example, the scientific and medical communities have long cited a common childhood condition, strabismus (crossed eyes or wall eyes), as a classic example of a developmental disorder that causes permanent changes in vision if it is not “corrected” within a critical period in early childhood. Surgeons may attempt to cosmetically straighten the crossed eyes of a child, but, unless the surgery is performed before the age of two, the chances of the child developing stereopsis or 3D vision are only twenty percent1. Moreover, experiments done on infant animals made artificially strabismic indicate that these animals do not develop the binocular neurons necessary for normal stereopsis and depth perception. Hence, an adult patient, strabismic since infancy, has been considered permanently stereoblind.
This was my story. I had developed infantile esotropia (crossed eyes) in the first months of life. After three surgeries when I was 2, 3, and 7 years old, my eyes looked more or less straight, but I lacked stereopsis. I could not see the 3D in 3D movies. As a neurobiology professor, I lectured on the development of the visual system, discussed the concept of critical periods, and often used my own history as an example of how well theory fit reality.
(en savoir plus…)
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