If a person sees a basketball coming, it is perceived as having a particular color, shape and velocity. "The knitting together, or what can be called 'neural gluing,' of all those different features so we see a unified object is a complex function done by the brain. Our research focused on how the brain does that," Shevell explained.
To study how the brain represents the color of objects, the researchers used a technique called binocular rivalry. The technique presents a different image to each eye and thus pits signals from the right eye against signals from the left.
"The brain has difficulty integrating the two eyes' incompatible signals. When the signals from the two eyes are different enough, the brain resolves the conflicting information by suppressing the information from one of the eyes," Shevell said. "We exploited this feature of the brain with a method that caused the shape from one eye to be suppressed but not its color."
The researchers first showed subjects vertically oriented green stripes in the left eye and a horizontally oriented set of red stripes in the right eye. "The brain cannot fuse them in a way that makes sense. So the brain sees only horizontal or vertical," Shevell said. For their study, the researchers developed a new form of the technique that allowed the horizontal pattern to be suppressed without eliminating its red color, which continued on to the brain.
At this point, the brain has a musical chairs problem. Both the red and green colors reach consciousness but with only the one vertical patternone object but two colors. The surprising result was that the "disembodied red, which originated
|Contact: William Harms|
University of Chicago