In most cases, they answer correctly. About 8 percent of men and one percent of women suffer from color vision deficiency, which is the inability to distinguish some colors and shades. It occurs when the color-sensitive cone cells in your eyes do not pick up or send the proper color signals to your brain. Red-green deficiency is by far the most common form. Even though he understands some of the ways this phenomenon is accomplished, Rowe, like patients with blindsight, remains astonished.
Visual information is carried from the retina along two separate neural pathways.
From there it is distributed to a number of higher visual areas in the brain. When the primary visual cortex is damaged, that information is lost. But not all visual input is jeopardized. A second neural pathway carries the remaining 10 percent of the information from the eyes, including data on object movement and location, to a visual center in the brainstem. From there it is transported directly to higher visual areas of the brain, bypassing the primary visual cortex.