"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.'"

Comments

how is this new?

[Anonymous Coward]

I remember reading about this back in the 90s...so what is new here?

Re:how is this new?

[ScrewMaster]

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.

Re:how is this new?

[kylben]

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...

Re:how is this new?

[ScrewMaster]

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.)

Re:how is this new?

[Anonymous Coward]

Saccades also provide oversampling, which increases resolution in the exact same manner an electrical A/D converter does.

Re:how is this new?

[socha23]

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.

Re:The illusions don't work for me

[More_Cowbell]

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.

You can test this yourself

[Mprx]

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.

Re:You can test this yourself

[Mprx]

The trick is basically to fall asleep without sleeping, as I assume microsaccades are not present during deep sleep. When I was a kid there was an "astral projection" fad in my school, and people would pass around books about it and try to learn the technique. It doesn't actually work, but you can learn to "shut down" parts of your brain while maintaining consciousness. As the article says, microsaccades are not motor noise, so you can learn to stop them. You can learn to consciously control lots of supposedly unconscious body processes, eg. you can make one hand hotter than the other, or change your heart rate at will. This kind of "body hacking" is the truth behind "ki" and other mystical things.

Re:You can test this yourself

[matthewncohen]

As a long-time meditator I can absolutely attest to this. It does not always happen, but there are certain states of relaxation in which my eyes stop doing this and whatever is in my field of vision becomes gray/green blurry outlines or eventually nothing at all until I move.