Susan Barry by Rosalie Winard

Susan R Barry Ph.D.

Eyes on the Brain

David Hubel: A View of a Scientist

Finding support where you least expect it

Posted Oct 15, 2013

When I learned at age 48 to see in 3D, despite having been cross-eyed since early infancy, I didn’t think anyone would believe me. After all, David Hubel and Torsten Wiesel had won the Nobel Prize in 1981 for their stunning work on vision, and, among their accomplishments, they had described the “critical period,” a period in early life when the young brain is most able to acquire certain skills. It was thought by many other scientists and physicians that the development of stereovision had a critical period. If a child was cross-eyed (had strabismus) and stereoblind throughout this critical period in early childhood, then it was impossible to develop stereovision in adult life. As a result, most people who were cross-eyed since infancy, as I was, did not receive vision therapy. Yet, it was vision therapy that taught me, at age 48, how to aim my two eyes at the same place in space so that I could fuse the images from the two eyes and see in 3D.

One day in late 2004, almost three years after developing stereovision, I decided that I had to put my story down in narrative form. That evening, as luck would have it, my husband and kids got involved in an all-night Monopoly game. So I retired to a quiet room in our house where I wrote a detailed letter about my vision to the author and neurologist, Dr. Oliver Sacks. I didn’t know Dr. Sacks personally, but I had read all his books in which he emphasized the importance of listening to his patients. I hoped he’d listen to my story too. Dr. Sacks did listen. Indeed, he came to visit me, and after many more letters and visits, wrote an article about me called “Stereo Sue” which appeared in the June 19, 2006 issue of The New Yorker and later as a chapter in his book, The Mind’s Eye. While doing research for “Stereo Sue,” he talked with David Hubel and Torsten Wiesel and described to them my experience. They encouraged him to explore my story further. As Dr. Sacks wrote in an April, 2005 letter to me, “they themselves are as open as can be.”   

After receiving Dr. Sacks’ letter, I rallied my courage and sent an email letter to Dr. David Hubel. Shortly afterwards, on May 27, 2005, I received his response:

“Dear Dr. Barry,” he began, “Thank you so much for the fascinating letter describing your experience with strabismus, and the dramatic recovery you describe following alignment of your eyes, and the therapy lessons.” He went on to say that his and Wiesel’s studies on strabismus had been incomplete since they had never tested to see if animals, who were made strabismic in infancy, could recover binocularity with re-alignment of their eyes. Thus, they had never established whether or not a critical period for stereovision existed. From all his research on visual development, Dr. Hubel suspected that the neurons necessary for stereovision were present in people at birth or shortly thereafter. So, the circuitry for stereovision may be present even in an infant with strabismus. Since the child cannot fuse images from his or her misaligned eyes, however, this circuitry does not mature. This leaves open the possibility for recovery of stereovision with proper training later in life.  David Hubel went on to predict (and rightly so) that, with  more fusion training, my stereo capabilities would continue to improve. He ended his email by offering to send me a copy of his latest book, Brain and Visual Perception. By the time I finished reading his email, I was trembling a little.

So began a three year correspondence with Dr. Hubel. When I printed out all our emails, they totaled to more than sixty pages of single-spaced print. As we continued to correspond, Dr. Hubel elaborated further on his extensive research. In addition to uncovering the basic responses of neurons in the early visual cortex, he and Dr. Wiesel had studied the effects of monocular deprivation (closure of one eye in infancy) and of strabismus (misaligned eyes in infancy) on experimental animals, but they had only established a critical period for monocular deprivation. These monocular deprivation studies were done to mimic the effect of a relatively rare human condition, the presence of a cataract in one eye of a newborn infant. Their experiments indicated that loss of vision in one eye during a critical period in early infancy produced changes in neuronal wiring that were not altered when the eye was reopened later in life. Although a critical period was rigorously established only for monocular deprivation, the critical period concept was then generalized by other scientists and physicians to infantile strabismus. But as Dr. Hubel wrote in Brain and Visual Perception about his work on strabismus, “A missing aspect of this work is knowledge of the time course of the strabismus animals, cats or monkeys, and in the monkeys the possibilities of recovery.”

While our emails mostly involved discussions of visual development and strabismus and of my latest stereo achievements, I soon discovered that Dr. Hubel had many other interests. He sent me some essays that he had written on topics such as thinking, qualia, and different styles of doing science. On May 25, 2006, I spent a morning with him in his office at Harvard Medical School. I brought with me some of my favorite vision therapy tools including a Brock string, polarized vectograms, and a small mirror stereoscope. We were joined for part of the time by a second vision scientist, Dr. Margaret Livingstone, as we experimented with all of these devices and looked at several stereograms and optical illusions that Dr. Hubel had produced on his computer. I asked him about the music stand and music sheets in his office and learned that he sometimes played his flute at work. He played the piano too, as I do, and we chatted about music. He had tools and (if I remember correctly) a lathe in a little room off his office and prided himself on teaching Harvard undergraduates how to work with their hands. For his own experiments, he had designed and built equipment and electrodes.

In late 2008, I sent Dr. Hubel a draft of my book, Fixing My Gaze, because I wanted his comments before the book went into publication. I was quite nervous about this, not just because I wanted to make sure I had represented his research accurately, but because I greatly admired the clarity and flow of his own writing. Dr. Hubel replied,

“I've just finished a first reading of your book, at last. I'm greatly impressed: it's an exciting story and one that's bound to not only be useful to anyone with similar problems with stereopsis, but to general readers who have no idea how important stereo vision is.” Then, he made several scientific suggestions and, to my surprise, located and corrected every misplaced comma or poor grammatical phrase. 

“Please forgive all the picky comments,” he wrote at the end of his email, “I was very glad that you were accurate in describing our work, and didn't extrapolate, as it is so easy to do so.” Finally, he added, “with my best wishes, and congratulations!! You write beautifully.” A few months later, he composed a strong endorsement for the back cover of my book.

When Fixing My Gaze had its final review at the publisher’s, the proof-reader commented that there were hardly any corrections to be made. That’s because, I thought to myself, the book has already been reviewed and proofed by a Nobel laureate.

David Hubel embodied for me the traits of a great scientist: a logical but creative and flexible mind, skilled with his hands and with writing and teaching, attentive to details without losing the broader context, generous, unpretentious, open, and kind. David Hubel passed away on September 22 at the age of 87. I will miss his friendship, warmth, and wise counsel.