When reading the chapters in the textbook about vision and all the different ways we rely on vision to perform the simplest of tasks, one question struck me – What happens to all these functions when someone is blind? How does this affect the way the brain operates? When searching for articles or even mentions in social media concerning blindness, I was dismayed to find a lack of articles concerning congenital blindness or even any kind of physical blindness – every article I came across in most psychology websites had topics ranging from inattentional blindness, color blindness (both physical and theoretical), and so on. I am disappointed to see the apparent lack of interest in how individuals, born blind, operate in their daily lives as opposed to how sighted individuals do so. I would have thought there would be a greater interest. That being said, I was able to find a few articles that addressed the topic of the effect of blindness on the brain.
This article in Science Daily examines how blindness causes the brain to make basic structural changes, suggesting that blindness not stemming from brain damage can cause the brain to rearrange itself, much as it does for the deaf. Since vision proves to be what supplies the brain with the majority of its input in a normal sighted person, one must assume that this huge lack in sensory input leaves the brain wanting. Scientists from the UCLA Department of Neurology suggest that the lack of this one vital sense enhances others in its stead. When these researchers looked at the brains of the blind, they noticed that the regions in the brain used for visual input were physically smaller in volume than those of sighted individuals. In those areas of the brain that didn’t use visual input, the same researchers noticed a vast increase in volume. The brain itself didn’t reduce in size – rather, the lack of the expected volume in the visual areas prompted the other areas to compensate. This particular study exemplifies and further proves the amazing plasticity of the brain; for people blind since birth or since infancy, this plasticity is further evidenced, as it’s the period in which the brain is much more modifiable than in adulthood. One of the areas in the brain these particular researchers at UCLA’s Department of Neuro Imaging found to be enlarged in the brains of the blind proved to be the frontal lobes, which are involved with, among other things, working memory. This, as well as other areas in the brain they found to be abnormally enlarged, suggested a possible explanation for the perceived enhancements in the sensory abilities of the blind.
Previous studies have found that when walking down a corridor with windows, the blind are adept at detecting the windows’ presence because they can feel subtle changes in temperature and distinguish between the auditory echoes caused by walls and windows. This may call into mind for some the sensation of echolocation, a sensory tool used by bats to sense their prey. James Roberts, a man that went completely blind at age 25 and subsequently became one the greatest travelers the world has ever seen, championed the use of echolocation to teach blind children how to independently live their lives. He cited “seeing with sound” as what helped him develop a sense of his surroundings; many researchers have used the story of Roberts as a baseline to further examine the link blindness and heightened awareness in other senses. While an intriguing thought, a flaw was immediately found – one can use echolocation for sensing larger objects and for moving around in the environment, but when reaching for a fork or a pen, echolocation as a tool falls flat. Blind people are not bats.
I would remind you about the finding in the first article by the researchers at UCLA, regarding the plasticity of the brain at a young age. Neuroscientists at McGill University conducted this study, testing blind and sighted participants in their abilities to sense changes in pitch and their ability to locate sounds. What they found was unprecedented. While the blind participants generally scored higher in the tests than their sighted counterparts, as the neuroscientists expected, an unseen variable was revealed. They discovered that the ages of the participants affected their performance. Participants “born blind did best, those who became blind as small children were slightly behind, and those who lost their vision after age 10 did no better than the sighted subjects.” Using this data, it was assumed that young brains, when in the developmental stage, can be rewired as to use their visual-processing areas for other purposes. Additionally, blind subjects that scored well in the study “were engaging both the auditory and the visual areas of the cortex. Those who scored low, as well as sighted subjects, “had little or no activity in the visual lobe.” Similar results were produced in studies on odor discrimination and tactile sensation.
Though evidently not much research has been done on the subject of the effect of blindness on the construction and use of the brain, these studies show that in most cases, blindness can heighten other senses. The variable of when the subjects became blind seems to be the biggest stimuli to keep in mind while conducting these studies. The only consensus scientists seem to have come to is that blindness does indeed amplify certain senses, though the degree to which this occurs in certain control groups appears to still be heavily debated today. One can only hope that the blind can find comfort in the apparent discovery that they are bats. If it’s any consolation, echolocation can be used to do pretty cool stuff, as evidenced by the blind Earthbender Toph Beifong:
I hope that there are more studies done on this topic, as I would like to see a more comprehensive theory behind the changes in the brains of the blind.