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"Microsaccades" Help To Refresh Your Field of View
Ponca City, We love you writes with news of research from the Salk Institute into small, unconscious eye movements called "microsaccades," the purpose of which has been in question for many years. A recent study showed that those movements were essentially responsible for maintaining a coherent image for interpretation by the brain. They are also the cause of a famous optical illusion in which a still image appears to move.
'"Because images on the retina fade from view if they are perfectly stabilized, the active generation of fixational eye movements by the central nervous system allows these movements to constantly shift the scene ever so slightly, thus refreshing the images on our retina and preventing us from going 'blind,'" explains Hafed. "When images begin to fade, the uncertainty about where to look increases the fluctuations in superior colliculus activity, triggering a microsaccade," adds Krauzlis.'"
I remember reading about this back in the 90s...so what is new here?
Nothing that I can tell. I was working as a software developer back in 1982 or so for a group of neuroscientists at a local university. One of the projects I worked on used a pair of glasses with infrared motion sensors on them to continuously track pupil movements. The idea was to monitor saccades for diagnostic purposes (they become exaggerated in, for example, people who habitually work in near-darkness ... like miners.) It was explained to me that it had been known since the sixties (if not earlier) that saccades were, at least in part, needed to avoid retinal fatigue. Early experiments were performed using a grain-of-wheat bulb literally glued to the eyeball. It was shown that when the image didn't move relative to the retina, it quickly became invisible.
It sounds like what these guys are doing is relating these involuntary eye movements to brain activity. That's interesting if not particularly novel: some of the people I worked for were doing this twenty-five years ago using EEGs. What's more interesting to me is that we're generally completely unaware of these eye movements, just as we're generally unaware of our blind spots. It's an impressive bit of (ahem) abstraction layering that the brain does for us.
The higher the technology, the sharper that two-edged sword.
Ditto - but back in the 70's. What next - wide ties and lapels, bell-bottoms and flood pants, nehru jackets and peasant skirts, platform shoes and disco?
Well, what the heck, if you can't get bail-out money, at least get research grant money.
Perhaps your eyes aren't perfectly in sync? My brother had this as a child (one eye would wander around while the other was looking straight ahead. The doctors 'cured' it by having him wear an eye patch for a while to strengthen the weak eye. He looks fine but he's never been able to see 3D images or movies.
Experience teaches only the teachable. -AH
I tested both illusions on the link provided in the summary and neither one had the effect on me that was claimed. What would that imply?
I tried them multiple times shifting my focus to different aspects of the image than directed just to see if it had any effect and it was no different.
Optical illusions don't work for everyone.
As an undergrad I had to sit through tests involving optical illusions for the psychology students, and in my case lots of the illusions didn't work. That got me excused from further tests, because they didn't want to make their precious stats go funny by including cases like mine (and about three other people in the class I recall).
Its not that unusual.
A learning experience is one of those things that say, 'You know that thing you just did? Don't do that.' - D. Adams
Am I the only one who shuddered a bit when I read this and thought about how it would feel to have a small object glued to the eyeball? I'm sure it was benign and performed by competent people who knew what they were doing ... but damn, that just sounds like a form of torture.
It is a miracle that curiosity survives formal education. - Einstein
Yes, however this research points to a particular part of the brain, the superior colliculus. That's interesting in a mapping sense. Perhaps not earth shattering, mind boggling interesting like a picture of the FSM, but interesting. Perhaps with better techniques, somebody will be able to tease the movements apart a bit better. As you alluded to in your post, sacchades are interesting from a clinical point of view. How about being able to manipulate microsacchades on a monitor and insert (evil-commercial-concept-or-product)? Your garden variety tinfoil goggles would be useless!
Well and again, yes. Do you want to have to will your heart to beat faster when you go up a flight of stairs? What happens if you forget that detail. The automaticity of our bodies allows us to concentrate on important things.
Like Slashdot.
Faster! Faster! Faster would be better!
If you can perfectly relax your eyes you can watch the image fade. Color fades before lightness, and eventually the whole image is just noisy gray. It's easiest if there's nothing visually interesting in your field of vision so you don't accidentally look at something and move your eyes.
Saccadic movements have been understood for a very long time, and it has pretty much always been assumed that part of their 'function' was to prevent the Ganzfeld effect and to facilitate in the construction of a representation in the mind of a wider field of view. It has also been known for a long time that the superior colliculus and brain stem are involved in those movements.
This work has begun to identify highly specialised structures in the superior colliculus that seem to control the saccades, and that *has* furthered our understanding of this aspect of perception.
I'd be surprised if the researchers themselves believe that most people thought saccades were 'mere 'motor noise''. I think when Krauzlis says 'scientists have debated the function, if any, of these fixational eye movements' he's being a good scientist and making a statement that does not have to be qualified to be true.
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That sounds like they are not very concerned about the accuracy of their stats. You mentioned that this was a type of test. What's the point of running a test if you have pre-determined the outcome? That is more properly called (by them, not you) a demonstration.
While the optical illusion tests you describe are probably not terribly important in the scheme of things, I mention this because it's surprising how many important things are handled this way. It's to the point that whenever I see a purportedly scientific study, my first question is "who funded it?"
It is a miracle that curiosity survives formal education. - Einstein
Am I the only one who shuddered a bit when I read this and thought about how it would feel to have a small object glued to the eyeball?
Anybody who wore contact lenses back in the 80's knows just how it feels. Especially if you were lazy, in college, and/or drank alot...
Insightful and funny are really the same thing, except one has a punch line.
Yes but the real reason for microsaccades is that almost all the photoreceptors in the retina are designed to detect changes, such as the onset or offset of illumination. Unless there is change in the field of view, the sensors will not fire and the brain stops receiving visual signals. Indeed, retinal ganglion cells (RGC) use a center-surround arangement so that they can detect movement in many different directions. There must be a slight delay between the signals sent from the photoreceptors to the center and side cells in order for the RGC to fire. This is crucial for the detection of things like edges, lines, etc. The brain is primarily a massively parallel discrete signal processor. The precise timing of signals is crucial to its operation.
Stare at that for thirty seconds or so then look at a blank wall and blink a couple times.
Damn you! why couldn't you have provided a link like that to a sweedish swimsuit model instead... now i got this bearded freak who looks somewhat familiar to me, i think his name is Buddy... something....
I tested both illusions on the link provided in the summary and neither one had the effect on me that was claimed.
If at first you don't saccade...
Insightful and funny are really the same thing, except one has a punch line.
That's interesting if not particularly novel: some of the people I worked for were doing this twenty-five years ago using EEGs.
The superior colliculus is fairly deep within the brain, so my guess is that they're using single-unit recording, which has been around for at least 30 years, to record from neurons. EEGs don't give readings at the neuronal level, anyway.
Stabilized images on the retina fade. Microsaccades prevent it from happening. I actually think I read an article about this in Scientific American in the 1960s. Certainly I encountered it in a perceptual psychology course I took in the 1970s.
As for illusions like the Enigma illusion, we were told that caused by small eye movements, amplified by a moire effect between the image and the afterimage. Maybe that was only the professor's guess, and the new study did something to pin it down, but it's not a very new idea.
"How to Do Nothing," kids activities, back in print!
The article in Wired seems to be a 'dumbed down for public consumption' version of an article that appeared in Scientific American in August 2007. The original was authored by Dr Susana Martinez-Conde and Dr Stephen L Macknik, and referred to a study they had completed in 2006. There is a preview available here:
http://www.sciam.com/article.cfm?id=windows-on-the-mind
unfortunately one would have to pay for the whole article as they are a subscription magazine. But the proof is in the preview, and if anyone should want more, I would encourage them to go to their local library and find the magazine there. The article in Scientific American is much more educational.
-Magdalene --"there are 10 types of people in the world, those who read binary, and those who don't"
Early experiments were performed using a grain-of-wheat bulb literally glued to the eyeball.
I first saw this in a Life Magazine article published in the late 1940s or early 1950s. That experiment used a mirror glued to a contact lens, not to the eyeball.
The mirror shifted an image on a screen to negate the retinal image's movement caused by microsaccades. The mirror was better for detecting the eye's angular movement than a light bulb would have been.
Well, the experiment I read did indeed have a small lamp assembly glued to an eyeball. It's been a long time, but as I recall the experiment wasn't about monitoring eye motion, but to determine what happens when the retina is exposed to an unchanging image. The article mentioned the fact that rabbits are pretty much unable to see anything unless it's moving (something about a lot of the visual preprocessing being done in the rabbit's eye, not in the brain.)
The higher the technology, the sharper that two-edged sword.
What's funny is, as I was concentrating on reading the last paragraph of your post, I was focusing on each word as I read it. Something seemed strange as I read, so I read it again, this time pausing for several seconds before moving to the next word.
Having already read the paragraph, I knew what it said. There was no sense of urgency in my mind, nothing to influence whatever part of my brain causes saccades to refresh my field of view so I could read the next word.
I could see each word very clearly when I first focused on it. By the time I moved my focus the the next word, I saw mostly gray.
Try it. Read this post a couple times, comprehend it, then focus on each word, individually, for several seconds.
Funny, for an instant I thought your post had some actual content, but for some reason all I can see now is the word "fnord" repeated over and over.
The higher the technology, the sharper that two-edged sword.
Peter Watts explores this subject (among many other interesting topics - including existence of free will, the chinese room, and the nature of empathy and sentience) in his newest book, 'Blindsight'. It's a pretty good read.
The book is available online here: http://www.rifters.com/real/Blindsight.htm. It's published under Creative Commons license.