EEG power spectra of children with dyslexia, slow learners, and normally reading children with ADD during verbal processing.

EEG power spectra were studied in two poor reader groups (with dyslexia and slow learning) and a normally reading clinic control group (with attention deficit disorder) as the children viewed strings of words and letters (seven categories). The children ranged in age from 7.5 to 12 years; 33 were girls, 86 were boys. Bilateral temporal and parietal sites and four midline sites were used. The major difference between groups was in the low beta band, where the ADD group had greater power at the parietal and midline sites. Also, the slow learner group had marginally greater low beta at the left than right temporal site, with the opposite trend found for the dyslexic and ADD groups. Across groups, power was greater at the right than at the left parietal site in the delta and alpha bands and at the right than at the left temporal site in the low beta band. Stimulus category effects were modest, with some alpha suppression to word strings, relative to letter strings, found in the poor readers. In correlational analyses, the combination of greater low beta and less theta power significantly predicted better reading and spelling. Results indicate that the adequate readers more actively processed the stimuli than did the poor readers.