What can visual deprivation do?
When is sight developed and how was this discovered?
When is sight developed? Researchers have studied this in animals like cats and primates.
David Hubel and Torsten Wiesel’s experiments showed that if a kitten is deprived of normal visual experience during a critical period at the start of its life, the circuitry of the neurons in its visual cortex is irreversibly altered. So how did they deprive a poor kitten?
Hubel and Wiesel sutured one eye lid closed of kittens right after birth. Around 6 months their eyelid was opened again. Recordings were than made of the electrophysiological activity in each of the kitten’s eyes. These recordings showed an abnormally low number of neurons reacting in the eye that had been sutured shut, and an abnormally high number in the other eye. Microscopic observation of the visual cortex showed that the ocular dominance columns for the eye that had been left open had grown larger, while those for the eye that had been closed had shrunk. Thats pretty bizarre huh? Hubel and Wiesel redid the experiment for cats who were abut a year old and showed no changed outcome of the electrophysiological activity in each eye. The adult cats must have celebrated with some cat nip to be happy to see again.
Obviously Hubel and Wiesel are very curious researchers so they set out to explore how this may affect primates. So they did the same thing on baby monkeys. They sutured one eyelid shut on baby monkeys and when the eyelids were opened again at 6 months of age, the monkeys had lost practically all useful vision in the eye that had been sensorily deprived. How rude. Yet recordings of electrophysiological activity in the ganglion cells of the retina of that eye, and the lateral geniculate nucleus cells for that eye, showed that these cells’ visual fields were normal and functional. It was only the primary visual cortex cells for that eye that showed practically no activity. In other words the brain didn't develop vision to work but the actual eye structures were developed and functional. Hubel and Wiesel did the same thing to adult monkeys but no vision was lost in those adult monkeys. I don't know how monkeys get high or celebrate but they were probably happy to see again as well.
So what do these experiments tell us? It basically concludes that the first 6 months of life are crucial and important for visual development. It also shows that mammals need the environment to develop vision. I feel way more connected to the world now! These experiments also tells us that a few monkeys and kittens were blinded for the rest of their lives BUT one more step of knowledge for mankind! (Trust me I feel the pain of the animals who were hurt in these experiments. I would def. hate to lose my vision for science too). Obviously it would be super unethical to recreate these experiments on humans but humans are actually 96% similar to the great ape species if we are talking genetics. So in conclusion, we definitely need our environment for vision development.
Have you ever thought, "Can I make myself hallucinate?"
Screw LSD, just grab a blindfold.
A very interesting study was done where they blindfolded thirteen individuals for up to four days (96 hours). The results? Some trippy shit. The researchers told the participants to wear the blindfold and record what they saw.
After the first twelve hours of the blindfold trip, these participants reported hallucinations such as shapes, figures and one person reported seeing a butterfly turn into a sunset. I was able to grab a hold of this qualitative research data and post some of the excerpts below:
“Subject 1, a 29-year-old woman, experienced a single hallucination 12 hours after blindfolding. It occurred while she was standing in front of what she knew to be a mirror and was of a green face with big eyes. The subject became very frightened by the experience."
"Subject 2, a 24-year-old man, experienced a broader range of images commencing a few hours after blindfolding and persisting for several hours after the blindfold was removed. Hallucinations at first included flashing lights, mirrors, lamps, trees, and full landscapes. At the conclusion of the second day of blindfolding, the images became more complex and he reported difficulty walking because of the “obstacles” he “saw.” For example, while taking a walk outside, he reported seeing “a ground of dirt rows, mounds of pebbles, or small stones that were running from upper left to lower right field of view and between them was running a small stream of water.” Over time, the images became a constant presence, and by the end of the study, he was reporting “ornate buildings of white–green marble” and “cartoon-like figures.”
"Subject 8, a 20-year-old woman, experienced an array of hallucinations similar to those of #2. The hallucinations appeared suddenly 12 hours after blindfolding and evolved into a series of different images, much as in a dream. She reported seeing a butterfly that became a sunset, an otter, and finally a flower. She also reported seeing cities, skies, kaleidoscopes, lions, and sunsets so bright she could “barely look at them.” “If there is a sunset or a sunrise I couldn’t look at the sun–because it was too bright–it would seem like all of this light would just collect where the sun was and I just could not look there.” She stressed the intensity of the hallucinations, commenting “sometimes they were much prettier, I think, than anything I have ever seen–I really wish I could paint.” She also reported that the hallucinated objects were always “in motion,” stating “sometimes they would move fast and sometimes slower."
More excerpts of the subject's experiences can be found in the actual research article. These results indicate that rapid and complete visual deprivation is sufficient to induce visual hallucinations in normal subjects. All of this is actually some pretty interesting shit. I'm actually planning on teaching a vision and perception class next semester.
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