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Blind Man Navigates Obstacle Maze Unaided
Posted by
samzenpus
on Thu Dec 25, 2008 12:18 AM
from the matthew-murdock dept.
from the matthew-murdock dept.
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."
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his eyes are fine (Score:4, Informative)
Its not that hard (Score:5, Interesting)
Parent
Re: (Score:3, Insightful)
I don't doubt it all. Lots of people can. The brain automatically enlists your other senses when one of them isn't working. That's why I think the article is a just a load of BS. I don't think the man saw anything. I think his brain was just able to use his other senses to accomplish the same goal.
Re:Its not that hard (Score:5, Insightful)
I would suggest having the blind man and an average-sighted man separately walk down a very well-lit corridor with randomly positioned (i.e., changing every iteration) obstactles 10 times, recording the amount of time each takes and the number of collisions. Reduce the amount of lighting by some increment and repeat the experiment. Continue reducing lighting until total darkness is achieved.
If the blind man is truly navigating by blindsight, both his course times and collision rates should roughly scale positively with those of the sighted man and inversely to the light levels. But then, that would be using the scientific method like the international team of neuroscientists in TFA (whom you are accusing of incompetence) did, so of course you wouldn't believe it...
Parent
Re: (Score:3, Interesting)
Brain Plasticity - his subconscious is figuring out how to make use of some form of input, to give him a sense that something is there.
I bet if he did it over and over, he'd get better at it. It'd strengthen the connections.
Re:Its not that hard (Score:5, Insightful)
Isn't it obvious or am I missing something here??
Blindfold the blind man and repeat the experiment with/without the blindfold. That will tell if vision is being used in any way.
Parent
Re:Its not that hard (Score:5, Funny)
I suggest a double blind test.
Parent
Re:Its not that hard (Score:5, Funny)
But blindsight is such a kickass name.
Parent
Re:Its not that hard (Score:4, Insightful)
Parent
Re:Its not that hard (Score:5, Interesting)
There is a video of a blind person on youtube who seems to be able to navigate just like a regular person through the use of echoes. He carries and uses a clicker to make sounds.
There is a group which teaches the blind to locate objects through echoes.
Parent
Re:Its not that hard (Score:5, Funny)
Bene Gesserit?
Sorry, I'm reading the book Paul of Dune which I just got as a Christmas present. Couldn't help myself... :)
Parent
Re:Its not that hard (Score:5, Interesting)
Do you mean this kid?
http://uk.youtube.com/watch?v=qLziFMF4DHA [youtube.com]
(That's part 1 of the documentary. Links to the other parts are in the info box.)
Incredible stuff, he rides a bike and everything!
What isn't explained though is how he's playing video games?
Parent
Re:Its not that hard (Score:5, Informative)
I call it being able to hear the "sound shadows" of objects, because that's really what they are - an object blocks sound, and that blockage is projected to the ear. With a good cane, I can navigate around tables, columns, and even position myself relative to peoples' voices to keep myself from running into them. It's quite amazing what you can tell with a good hallway, and a constant sound source (soda/vending machines are good). For example, an open, echoy space usually means a stairwell.
Also, randomness ... the first time I went to post, my screen reader [gnome.org] was very sluggish and crashed. I guess Slashdot hates blind Linux users.
Parent
Re: (Score:2)
Re:Its not that hard (Score:5, Interesting)
That's very cool. It's also proof of how amazing the brain is - the part that makes a 3D model of your surroundings will adapt to any sort of useful input. With just sonic shadows you're working with very limited data, but even so: the navy has spent a ton trying to develop good passive sonar, and it sounds like you're better at it than the technology. Now if someone could just invent a sonic lens, it would close the gap. The only reason light gives better 3D positional information is the lens (though it would also be helpful to hear sub-millimeter wavelengths, as 20 kHz doesn't give much precision).
Parent
Re: (Score:3, Interesting)
Sighted people can learn this, too. I worked in an office where I had my back to a doorway, and through that door was a room full of servers. No one was ever able to sneak up on me because I could hear their sound shadow as they walked by the servers. It took me a while to figure out how I was aware of them, because it wasn't really a conscious thing at first.
Re: (Score:3, Informative)
While that is true, that's not what's happening here. In the case from TFA, the man is not conscious of any visual sensory input, but IS able to subconsciously make use of visual information. Also from TFA, he has the same subconscious responses to being shown pictures of people's faces displaying various emotions and other responses that cannot be due to echolocation.
In another experiment (not part of TFA) a number of subjects with cortical blindness were able to accurately state which direction a dot of l
Re:his eyes are fine (Score:5, Insightful)
Without a working visual cortex, nothing from the eyes enters the brain. At all.
It would be really nice if hypothesis and biology worked like that, where biology followed our hypotheses, but it doesn't. It would be interesting to see an fMRI, or see if he could navigate the maze with earplugs or some way of throwing off air pressure. Assuming it can't possibly be his eyes connecting to some other part of the brain simply because textbooks say the eyes connect only to the visual cortex is not a safe conclusion.
Parent
Re: (Score:2)
Read the article. Carefully. There's good evidence from other mammals that subcortical structures are activated in response to particular visual stimuli, independently of the cortex.
Re:his eyes are fine (Score:5, Informative)
Parent
Re:his eyes are fine (Score:5, Informative)
"Without a working visual cortex, nothing from the eyes enters the brain. At all."
Whoopsie. Apparently you didn't know about the body of work showing that there are connections between the retina and subcortical areas as well as the striate cortex. Of course, if you'd read the article, you would have noticed they mentioned that.
Yes, I read your other comments, including the one where you claim to have read the article. To summarize: you don't think it's possible... because .
Parent
Re:his eyes are fine (Score:4, Informative)
If you RTFA (I know, a big assumption -- Google can take you to the no-registration-required SciAm version), they say that scientists suspect there are other pathways where the info is getting into his brain, even though his visual cortex is totally destroyed on both hemispheres. This is the first blindsight demo with NO visual cortex, and thus seems to suggest strong that there are some alternate pathways going on. He can also react to facial expressions.
Parent
Re: (Score:3, Informative)
The signal from the optic nerve doesn't go exclusively to the primary area of the visual cortex- it forks at the lateral geniculate nucleus before it gets there and some also goes to subcortical targets which provide functions like the flinching reflex. These are older pathways and modern vision evolved by eavesdropping on the signal.
Re:his eyes are fine (Score:5, Informative)
Maybe the problem is that TFA tried to make the science more approachable to people, but you obviously don't understand a single thing about blindsight. This is nothing new at all. In layman's terms, the participant still experiences visual sensation but not visual perception -- they can still see, but they are unaware of it. What is significant in this case is the extent of the damage to the visual cortex. The sensory compensation of congenitally blind people is incredible, but this is an entirely different phenomenon.
Sight doesn't "occur" in the eyes, but there are a number of subcortical structures the information passes through before it gets to the visual cortex. Which, oddly enough, is exactly what they say in TFA, which you claim to have read. They specifically say that the "visual areas of the brain" did NOT "light up", so I have no clue what you're babbling about.
The entire point of the article is that the extent of subcortical visual processing (which we are unconscious of) is greater than most people realise. So feel free to read it again and appreciate what is actually a well-established neurological phenomenon.
Parent
Re:his eyes are fine (Score:5, Informative)
http://www.amazon.com/Physiology-Behavior-MyPsychKit-Neil-Carlson/dp/0205593895/ref=pd_bbs_sr_1?ie=UTF8&s=books&qid=1230187013&sr=8-1 [amazon.com]
Chapter 1 has a short item on blindsight and it's relation to consciousness. You should really read chapter 1 of this book.
IMHO, sight doesn't happen as much in the eyes as it does in the brain.
Well, that's how the brain does its thing. Your eyes, ears, nose, skin, are instruments that extend from the brain. Data that flows from your senses to your brain lacks meaning until the brain processes it.
A few posts earlier you say:
( http://science.slashdot.org/comments.pl?sid=1072951&cid=26228425 [slashdot.org] )
Without a working visual cortex, nothing from the eyes enters the brain. At all.
Blindsight does not imply that the visual cortex does not "work". Have a look at http://en.wikipedia.org/wiki/Primary_visual_cortex [wikipedia.org]
Data still flows from the eyes over the optical chiasm to the primary visual cortex (the cortex around the calcarine fissure in the occipital lobe). From there, there are multiple "streams" of visual data. One of those streams is the one that "enters" consciousness.
It is the absolute certainty with which you refute the previous, and the postulation of the following near-superhuman senses that make you appear rather uninformed and quite arrogant.
Most likely, he is using sound or air pressure. Blind people can often maneuver by hearing things like subtle changes in sound of footprints, etc., echoing off of or being aborbed by walls, etc. There are also subtle changes in air pressure as you approach obstacles, and that can often be 'felt' by blind people.
Take a biological psychology course or your own medicine (your signature)
http://www.scholarpedia.org/article/Blindsight [scholarpedia.org]
http://en.wikipedia.org/wiki/Blindsight [wikipedia.org]
Parent
You know what they say (Score:5, Funny)
this explains Zatoichi (Score:2)
Sighted Persons Unable to Navigate TFA (Score:5, Funny)
Re:Sighted Persons Unable to Navigate TFA (Score:4, Funny)
Parent
Turn in your nerd badge (Score:5, Interesting)
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"
Re: (Score:3, Insightful)
That's because their navigational algorithm is much simpler. put your hand on the right wall and follow it.
You'd be surprised how much easier things can get when you eliminate useless data. This, however, seems to be a more noteworthy experiment in that it was more than just a regular old maze with two ends.
Perhaps this will be the first step in discoverin
Uhno (Score:5, Informative)
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.
Re: (Score:2)
I jest about doubting you, but I'm serious about the TVs. Those things are loud!
Recursion... (Score:2)
My daughter confirmed this story for me a year ago (Score:5, Interesting)
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
Blindsight, Deafhearing and Alien Limbs (Score:5, Informative)
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.
Re:Blindsight, Deafhearing and Alien Limbs (Score:5, Interesting)
There's also other differences as well. Some women, for instance, have see a fourth set of colors, which gives them a much greater low-light ability (a couple for every thousand women, IIRC) as well as do great things in the visual arts. Other people have vision that extends a bit beyond the normal ranges as well. A good example if this is the typical "normal" body temperature. It was obtained by sampling a large number of people and averaging the result. Vision, hearing, and other senses are similar. So it's not surprising that the occasional blind person can actually tap into these if theirs happen to naturally be more developed than normal.
By tapping into the secondary pathways like this, I can "see" about twice as well as most people in the dark(though it's not really "seeing" like reading a paper or like a cat does). And, as DynaSoar mentioned, I can literally run through areas at night and not hit things as long as there is even a tiny amount of light.(doesn't work in caves/absolute pith black - tried that - heh)
Note - the skill can be learned, though some see better at night than others. I suspect their vision is shifted a bit more towards the infrared or their iris' are a bit larger. It took me about 2-3 years to develop it when I was growing up. My friends and I always spent a lot of time playing outside at night and some of us got pretty good at avoiding things in the dark. The hard part was learning to just trust your instincts. It's a odd feeling, though, as you only notice things a split second before you normally would hit them if you're moving faster than walking speed.
I found that a trick to doing this - and you can try this as well - is to learn to defocus your eyes during the day. Animals do this to track movement. It's a common trick hunters also use to track and find game. If you can then also do this at night, it basically shuts off a lot of your brain's trying to strain itself in low light. Since the average person's brain normally focuses intently upon just a small area in front of them, expanding that to your entire field of vision makes a huge difference.(though as noted, you can't focus on specific objects at the same time) Often, even if you can't actually see details, your eyes will notice things like faint reflections, movements, and so on.
My ex? She's nearly completely blind about 5 minutes after dusk. Opposite end of the scale as it were.
Parent
What's his midichlorian count? (Score:2, Funny)
Obi-Wan Kenobi would be proud.
See It Now (Score:5, Interesting)
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.
This works because... (Score:3, Interesting)
Video of the experiment - from BBC (Score:5, Informative)
http://news.bbc.co.uk/2/hi/health/7794766.stm [bbc.co.uk]
Ps: Found this after 'Submit'ting to slashdot
Video at NPR (Score:2, Informative)
A video of the blind man walking down the corridor accompanies this story at National Public Radio [npr.org].
Re:Ben Underwood (Score:5, Informative)
TFA specifically states that they ruled out echolocation.
Parent
Since you apparently read TFA (Score:2)
(Am I going to hell for posting this on Christmas eve?)
Re: (Score:2)
TFA specifically states that they ruled out echolocation.
Well they said they found no evidence that he was, I'd still like if they elaborated that they gave him earplugs or something, even footsteps could give him enough audible info to navigate.
Ideally I'd like some mention of a control using a blindfold or something. From the sounds of it he wasn't truly blind, the eyes worked fine but signals either weren't getting to the brain, or weren't getting processed by the visual cortex. They seem to be suggesting the visual info is still somehow being processed to aid
Registration required (Score:5, Informative)
From bugmenot.com [bugmenot.com]:
Username: arizonafrank
Password: poochie
Parent
Re: (Score:2)
We sense it. We transmit it. Assuming we've solved all the mysteries of the body is naive.
I think you are the one making "assumptions."
Re: (Score:2)
Let me just say, bahahahahahahahaha.
Re: (Score:2)
Except they said they ruled out echolocation. Read the goddam article.
Re: (Score:2)
For as long as I can remember, I've been able to tell when I was near a wall in a dark room, or with my eyes closed. I don't know if I'd describe it as sonar per se, but I can also tell if someone is standing close to me, no matter what our relative positions are.
FWIW, the last time I tested it with a tone genererator, my hearing topped out somewhere around 25Khz. I'm sure it's far lower now, but I can still tell if there's a CRT monitor powered on anywhere within fifty feet of me or so.
-jcr