"Microsaccades" Help To Refresh Your Field of View 96
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.'"
Re:The illusions don't work for me (Score:5, Informative)
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.
Re:how is this new? (Score:5, Informative)
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.
The Real Reason Is Change Detection (Score:3, Informative)
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.
Re:how is this new? (Score:4, Informative)
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.
WTF? We all knew about this in the 1970s (Score:3, Informative)
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.
Go to the Source and the water is Sweeter (Score:2, Informative)
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 [sciam.com]
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.