Neuroscientists in the USC College of Letters, Arts and Sciences have conducted a study examining the magnocellular (M) and parvocellular (P) visual pathways. The M pathway processes motion and brightness where as the P processes colors and fine details.
The study on 55 children aged 8 to 12, with 28 identified as dyslexics and 27 as non-dyslexics. The children hit a button when they saw a rectangle of black-and-white stripes appear on a computer screen. By adjusting how much the stripes contrasted with the background, the team compared the ability of the children to detect two different patterns, a flashing pattern that stimulates the M pathway and a stationary one processed by the P pathway. Dyslexics and non-dyslexics were equally able to detect both M- and P-type patterns. But when researchers added visual noise, in the form of TV “snow”, on top of the pattern that a difference emerged. Patterns had to be 10 percent more contrasting for children with dyslexia to detect them compared with non-dyslexics.
USC Press Release