Introducing the brain: we learn to see (Introduction)

by David Turell , Saturday, June 19, 2021, 20:05 (1251 days ago) @ David Turell

A book review about man who had to learn to see after surgery at age 15. He never developed the sight we normal folks have:

https://www.wsj.com/articles/the-boy-who-learned-to-seeand-what-he-teaches-us-about-vis...

"To ask a blind person to acquire the sense of sight after childhood is to ask them to reshape their identity. They may have functioned quite independently when blind but now find themselves as vulnerable as a young child. With their new sight, they can see but cannot recognize a flight of stairs or a loved one’s face. Bombarded by visual stimuli they don’t understand, many who gain sight in adulthood become despondent, reject their vision or even lose the will to live.

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"As the philosopher Alva Noë has written, “Perception is not something that happens to us, or in us. It is something we do.” We move our body, head and eyes to look and listen, to take in information about the world. Since we direct what we see, developing vision as an adult is an intensely active process. A new pair of eyes won’t lead to vision unless the owner of those new eyes pays attention to what he is sensing and figures out its meaning.

***

"Nine months after the second surgery, one of the lenses moved out of position, causing Liam to experience double vision. The lens was replaced, and this time the improvement in acuity was immediate. The gains in acuity after the first two surgeries may have occurred gradually because it took the brain some time to process all the new information that the eyes could now provide. Not only did his acuity improve tremendously, but his nystagmus was reduced. His binocular vision improved, as did his depth perception, albeit slowly.

"But the improvements were discombobulating. Surgery plunged Liam into a world of sharp lines and edges. He now saw lines wherever there were changes in color, light or texture; where one object ended and another began; where an object in front occluded an object behind; and where a shadow was cast on a surface. While we all see lines at the boundaries of objects or shadows, we know where these lines belong. We recognize an object immediately—all of its parts combine together, instantly and effortlessly, into a single unit. But after a childhood of near-blindness, Liam did not recognize the lines as boundaries of known objects. Instead, he saw a tangled, fragmented world.

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"After his surgeries, Liam’s eyes provided his neurons with the input they had long been waiting for. But he lacked the visual experience of seeing beyond a few inches, so he had not yet developed the “top-down” processing that organizes these local details into coherent objects and landscapes. As a result, he had to rely heavily on “bottom-up” processing and consciously piece together the visual world from its parts.

“'Up close,” Liam wrote, “things are more like objects than visual chaos, but there is a definite difference when I see something further away. Those objects have no meaning, and I struggle to tell if a bar of color is the front of a truck or side of a bus or roof of a building. If people even stand slightly further away and talk to me or say hi from down the hall, it has a very different feeling, and it doesn’t seem as real.”

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"Though we are not born with an innate ability to recognize household or most natural objects, we may be born with a rudimentary face-detecting skill. Infants just nine minutes old exhibit a preference for looking at a human face. This remarkable fact was discovered during an experiment in which different pictures were moved across a newborn’s field of view. When a face pattern (an oval for the head, enclosing shapes that looked like eyes, a nose and a mouth) was waved in front of the baby, the child would turn his or her head and eyes to follow the pattern. But if the features were all mixed up so that the pattern no longer resembled a face, the infant did not follow the pattern as reliably or for as long."

Comment: Just as we learn to walk we learn to see, and obviously we learn to feel, to hear, to taste, etc. Our brain is designed as quite helpful to build up an encyclopedia of recorded knowledge to help us navigate living. This is the blank slate aspect of the newborn brain, I have referred to in the past. What is not blank is our congenital inheritance and our experiences as we develop from infanthood. I've not reproduced a huge section of study about optic neurophysiology that the article contains.