Patterns of task-related slow brain potentials in dyslexia.

Six dyslexic youths who met the Hughes and Denckla criteria of "dyslexia pure" and 10 normal control subjects were investigated with DC recordings of task-related cortical negativity using 10 leads over the right and left hemispheres. Potentials were recorded during the following tasks: reading, orthographic error detection, letter series, word assembly, word fluency, finding of antonyms, and viewing of Necker cubes. Both groups exhibited greater right hemisphere negativity during the Necker cube task. Whereas controls revealed greater left hemisphere negativity during linguistic tasks, the reverse was found with dyslexics. The right shift was pronounced with the reading, orthographic error detection, and antonym conditions. Differences between the two groups were also found for the pattern of cortical distribution. We conclude that dyslexia is associated with changes in the lateral distribution of cortical activity during certain types of language processing.