Visual information processing and cerebral activation in dyslexic boys: Quantitative EEG analysis during discrimination reading tasks.

The hypothesis that in developmental dyslexia the integration of visually presented information and language processing is dysfunctional is tested. Results of processing visually presented letter strings during EEG recordings are presented. The task difficulty of the letter strings was standardised individually and automatically by a computer program. EEG was recorded during rest conditions and different levels of reading performance. 30 developmental dyslexic boys who met the Denckla criteria of "dyslexia pure" and 28 matched control subjects were investigated. The main replicated results were: (1) There was a delay in dyslexic children in processing visually presented letter information, (2) there was no deficit in sustained attention in developmental dyslexics, (3) increasing cognitive activation and reading performance resulted in a faster attenuation of relative alpha power in dyslexics compared to controls, and (4) the dyslexic group did not reveal characteristic focal EEG features when task difficulty was standardised individually.