July 21, 2010
Chance Discovery Sheds New Light On Vision
A chance discovery has led Australian scientists to question key assumptions about how our vision works.
Their results show the brain is more flexible and versatile than the computer it is often likened to, and even may lead to new tests for blinding diseases such as glaucoma.
Previously it was thought that the brain's ability to discern color depends on a specialized nerve "Ëcolor channel', but now, say researchers from The Vision Centre and Sydney University, it appears some color-sensing cells can also signal movement.
"In this research we discovered that blue sensing cells not only can respond to black and white patterns, but surprisingly are even sensitive to the direction of pattern movement," explains team leader Professor Paul Martin.
"In diseases like glaucoma, your color vision is impaired. Now we have discovered that the color cells can also sense black and white and movement, that gives us a new way of testing to see if the cells are healthy or not. Our colleagues in The Vision Centre include experts at designing tests for glaucoma, and they now have a new clue that may make their tests even more sensitive," he adds.
The serendipitous finding happened when young researcher Maziar Hashemi-Nezhad decided to carry out an unplanned experiment that came up with a totally unexpected result.
"It was chance. Maziar was in the lab, late at night, and decided to see if he could get color vision cells to respond to a moving black and white pattern "“ something which was considered most unlikely because the prevailing scientific view was they respond only to color. He saw an immediate response," Prof Martin says.
"This is an example of how "Ëblue sky' science may lead to a practical outcome. The goal of this work is not to study glaucoma, it is really all about trying to interpret the signals on the "Ëfax line' that connects the eyes to the brain "“ this discovery takes us one small step closer to understanding what is really going down the fax line," he explains.
"For a long time we've had an image of the brain as a kind of computer, with particular pathways "“ or "Ëwires'- for particular nerve signals. Now it is becoming clear the wiring is a lot less precise than a computer. But imprecise wiring is actually flexible because it creates many backup pathways to compensate for aging and damage," Prof. Martin says.
The researchers' paper "Receptive field asymmetries produce color-dependent direction selectivity in primate lateral geniculate nucleus" by Chris Tailby, William Dobbie, Samuel Solomon, Brett Szmajda, Maziar Hashemi-Nezhad, Jason Forte and Paul Martin has just appeared in the Journal of Vision (2010), Volume 10 (8), pages 1-18.
The Vision Centre is funded by the Australian Research Council as the ARC Centre of Excellence in Vision Science.
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