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Blind Man Navigates Obstacle Maze Unaided
iammani writes "The NYTimes runs a story about a blind man (blind because of a damaged visual cortex) successfully navigating an obstacle maze, unaided. Scientists have shown for the first time that it is possible for people who are blinded because of damage to the visual (striate) cortex can navigate by 'blindsight,' through which they can detect things in their vicinity without being aware of seeing them."
his brain is still able to make use of the input comming from the eyes which are undamaged. interesting.
If you mod me down, I will become more powerful than you can imagine....
Blindsight is 20/20.
TFA specifically states that they ruled out echolocation.
Always going forward, 'cause we can't find reverse.
After some practice I could do it myself. So can you. Start with a hallway with hard walls and walk down it blindfolded using your ears. It may help if you make a high-pitched sound. (at least high-pitched sounds are easier for me) I can only avoid large objects that don't aborb sound myself, but I bet I could get better.
If video games influenced behavior the Pac Man generation would be eating pills and running away from their problems.
Doctors remain baffled at the inability the majority of Slashtards to read and comprehend a simple article summarizing a medical experiment, despite apparently functioning visual systems. "They just wouldn't quit insisting that the subject of the experiment used echolocation to navigate the obstacles in the hallway, no matter how clearly and explicitly the article explained that the possibility had been ruled out," say baffled researchers. "We don't think their brains are wired correctly."
For those whose curiosity hasn't entirely been replaced by fashionable knee-jerk skepticism, your optic nerve does not only terminate in what we think of as primary visual cortex, it sends projections to other areas as well, though these areas do not contribute to what most of us think of as "sight"
This is hardly the first time blindsight has been demonstrated. I recall Ramachandran at UCSD doing experiments on it a while back.
One of the more mind blowing things I read in 2008 was the discovery of a third type of visual receptor besides rods and cones. Essentially there's a third type of receptor that only detects sort of gross levels of light, and feeds directly into the system which regulates your circadian rhythm and is used for some other purposes. People that were completely blind were able to tell when light levels were fluctuated in a large way, like walking in front of a TV, and be totally puzzled how they knew that, since it didn't register as sight at all for them.
The fact that these neuroscientists would call it the first evidence for blindsight means that either they really didn't read their papers very well, or it was a bad article summary on Slashdot.
From bugmenot.com:
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No existe.
My daughter had a stroke before she was born, and as a result, she suffers from Cortical Visual Impairment (CVI), like the subject of this story. At nine months of age, she couldn't tell light from dark, which really screwed up our sleep cycles. Her eyes were fine, but her brain could not process the signals that they were sending to her.
Eventually, she did regain some amount of vision, but her hearing is still her primary way of "seeing" things. Whenever we go into places that are pitch dark, my wife and I are walking into things left and right. My daughter, on the other hand, cruises right around like a bat. She hears walls and other obstructions, and corrects her course to avoid them. Her object avoidance skills greatly diminish when she can use her eyes to see, as her brain has to work much harder to decode what she sees with her eyes.
-- Len
There are two distinct causes of blindsight (and deafhearing and alien limb syndrome), damage to the primary sensory cortext but not the secondary or assosiation cortices, and damage to the association cortex, but not the sensory.
The latter is easy to explain. The person can perceive, but can't incorporate the fact of it into their conscious experience. They can't "own" the perception. This is very often found in damage to the somatosensory cortex which leaves partial paralysis. Often the person can't perceive the limb attached to their body as 'theirs'. Sensations in the limb do not become perceptions for them. Similarly, vison and hearing can occur, and the brain can make use of the data, but the person can't perceive it because it's not coming from "them".
The former is harder to explain. There seems to be a parallel visual (and auditory) system through which information can pass and the brain make use of, but which bypasses the association cortex. The person can't perceive normally, but if tested they react as if they can. They can, for instance, consistently "guess" the number of fingers shown them. There is a similar system for somatosensory. Perception of touch to, say, the hand, has highly detailed "maps" elsewhere on the body. For the hand it's on the cheek and on the back just below the shoulder. Just why this secondary pathway exists is a mystery. But it does, in most people.
Around 20 years ago in Coevolution Quarterly there was an article about a 'school' in (IIRC) New Mexico that taught people to use their blindsight to navigate in the desert at night. The secondary visual pathway that persons with the second form of blindsight use, exists intact in everybody. It's not something you develop because of damage, it's something that's there in case you need it but below the level of consciousness so as not to interfere with normal perception. Occasionaly hunters, hiker/campers or survival technique practioners will hear of a person who can literally run through a pitch black forest without running into anything. These people have the ability to react to the subliminal perception from the secondary visual system in what occurs to them as instinctive reactions because they don't consciously perceive anything.
"I may be synthetic, but I'm not stupid." -- Bishop 341-B
Obi-Wan Kenobi would be proud.
If you ever want to see this in action, there's a very simple experiment you can do. Put a quarter inside a ring of five loons (Canadian $1 coins). Put another quarter inside a ring of five dimes. The quarter surrounded by dimes will look larger than the other one.
Reach out and pick one up. Put it back. Pick the other one up. Put it back. You'll notice that even though your eye is telling you the two quarters of different sizes, your fingers will automatically spread out just the right amount to pick up either coin.
The illusion works for your regular visual system. The unconscious one gets the answer right.
I've calculated my velocity with such exquisite precision that I have no idea where I am.
...the brain has a layered architecture. The more primitive brain has its own visual processing system. Evolution has built connections with this system and the parts of the brain that deal with awareness. Lose this connection and you can still "see", but not be aware of them (at a very high level).
Heres a video of the man walking through the obstacles - from BBC
http://news.bbc.co.uk/2/hi/health/7794766.stm
Ps: Found this after 'Submit'ting to slashdot
A video of the blind man walking down the corridor accompanies this story at National Public Radio.
It is not mentioned very clearly in the NYT article, but it is mentioned in the original Current Biology paper: this patient has BILATERAL lesions in both the left and right visual cortices. IMO, this is what makes this case especially interesting.
Of course, blindsight has been demonstrated many times before, but always in patients with unilateral lesions. This has some methodological advantages (the patients can act as their own control), but the unilaterality has also been criticised. Maybe these patients make microsaccades, maybe some light is reflected by the nose into the other eye halves, etc. In short, maybe some information reached the intact hemisphere.
This is not possible in the present patient, and that is especially interesting. AFAIK, this is the first and only patient with a bilateral blindsight.
-- Geert