Moving clues to dyslexia.

A new study adds to evidence that the reading disability known as dyslexia involves an inability of the brain to coordinate the perception of objects moving quickly, such as that of letters scanned on a printed page.

Neuroscientist Jonathan B. Demb of the University of Pennsylvania Medical School in Philadelphia and his colleagues recruited 10 adults, half previously diagnosed with dyslexia. The researchers used functional magnetic resonance imaging (fMRI) to record cerebral blood flow, an indirect sign of neural activity, as volunteers tried to pick out the faster of two moving gratings shown on a computer screen.

Compared with good readers, dyslexics were less successful and exhibited reduced activity in the primary visual cortex and related brain areas involved in motion perception (SN: 3/7/98, p. 150), the scientists report in the Sept. 1 Journal of Neuroscience. The slowest readers displayed the lowest blood flow in these regions.

It remains unclear whether the motion perception problems found in this study cause dyslexia by themselves or are part of a larger deficit in information ordering, the researchers say.