- Mar 2023
// Good source to illustrate how we construct our perceptual realities
Although Virgil, MM and others like them certainly possess a rudimentary form of vision, decades of visual deprivation may never be completely redeemable. The human brain has an amazing capacity for plasticity, but there are some things that it cannot do. MM will likely never see the way that we see.
// Gradients of perceptual experiences of reality - The sense impaired teach us something fundamental about human nature. - The majority of non-sense-impaired people create the cultural norms of reality - but this reality can be very different for the sense impaired - Our reality is, to a large extent constructed from by our brain and depends on critical sensory inputs - But what is the brain itself, this magical organ that makes sense of reality? - The answer is going to vary depending on the subject experiencing it as well
MM's visual capacities continue to improve, but he also remains somewhat uncomfortable with his new sense. As a blind person, MM became extremely proficient at skiing, with the help of a guide to give him oral directions. After his eyesight was restored, skiing frightened him. The trees, snow, slopes, people -- everything whizzed by him, chaotic and uninterpretable. After much practice, he is now a moderate sighted skiier -- but when he really wants to go fast and feel confident, he closes his eyes.
// In Other Words - when sensory organs fail while we are young - we may construct different interpretations, and therefor experiences of our perceived realities - and adapt to them effortlessly. - If not for social stigma from the normative population, they would not know the difference - once we've adapted to sensory abnormalities, - a return to the normative way of experiencing reality via some medical intervention - that corrects a deficient sensory modality - is not guarantied to create the normative perceptual experience ordinary people have
There is a window of opportunity in youth, often called a critical period, during which the brain can best form neural connections that correspond both to retinal images and to practical experience. During the critical period for the visual cortex, normal visual input is required to wire everything correctly. If input is missing during this period, the brain's links will probably not be built correctly. In fact, brain tissue ordinarily used in visual processing might even be taken over by other systems, perhaps tactile or olfactory systems. Some of MM's visual abilities lend further support to the theory that he missed a critical period of visual development. He is quite good at visual tasks that involve motion. Tasks that stumped him at first often became solvable if motion was incorporated into them. He became able to detect the circular patterns in random noise if the patterns were moving. And he began to see the "square with lines" as a cube if the lines moved, and the cube appeared to be rotating. At the end of their evaluations, the researchers saw some patterns emerging in MM's visual abilities and deficiencies. His ability to detect and identify simple form, color, and motion is essentially normal. His ability to detect and identify complex, three-dimensional forms, objects, and faces is severely impaired. The researchers have a tentative explanation for these variations in visual skill. Motion processing develops very early in infancy compared with form processing. By the time MM lost his eyesight in the accident, the motion centers in his brain were probably nearly complete. So when he regained some eyesight in his forties, those connections in the brain were ready to go. The parts of the brain that process complex shapes, however, do not develop until later in childhood, so MM's brain likely missed its chance to establish those particular brain connections. The authors also propose that our brains may retain the ability to modify and refine complex form identifications throughout life, not just throughout childhood. New objects and faces are continually encountered throughout life, and our visual processing centers must be able to adapt and learn to see new shapes and forms. MM's brain never had the chance to learn.
// summary - MM could perform better if motion was involved - It is known that motion processing develops very early in infancy, whilst form processing occurs much later - the researchers hypothesized that when MM had his accident, he had already experienced enough motion processing to be familiar with it, but had not had any opportunity to perform form processing yet. - He missed the early opportunity and other brain functions took over those plastic areas, crowding out the normally reserved functional development
his problems didn't seem to be vision deficiencies so much as visual interpretation deficiencies. And deficiencies of this sort lie not with the retina's ability to perceive light and color, but with the brain's ability to process the retina's signals correctly. We usually do not think of the above problems as involving interpretation, because we have performed these interpretations so many times, and from such a young age. But since MM lost his sight at an early stage of development, since he had no visual input into his brain after age three, the researchers suspect that the visual centers in his brain did not develop normally -- and now, they likely never will.
// Interpretation, rather than sensory deficiency - paraphrase - summary - This loss of normative vision is due not to anything physiological, - but to the way the brain has been starved of real-life training experiences since childhood - the early years of our childhood are critical - to train the brain how to interpret the sensory signals - in order to form the normative perceptions we experience as adults
Scientists and surgeons are slowly learning how to remove constraints on the eye's ability to see; unleashing the brain's ability to see is another story.
// The brain plays a critical role in sight, without it, we can't see. There's more to it than the eye sees!
constructing our perceptual reality
- Oliver Sacks
- constructing visual perception
- Deep Humanity
- constructing reality
- An Anthropologist on Mars
- The story of Virgil
- constructing our sense of sight
- constructing our perceptual reality
- constructing our reality