Developmental dyslexia and attention dysfunction in adults: brain potential indices of information processing

Event-related brain potentials (ERPs) were recorded from a group of 13 men with severe developmental dyslexia and 15 matched normal controls. Auditory and visual stimuli, presented in separate reaction time tasks of graded difficulty, were used to elicit ERPs. No group differences in P300 were seen under relatively undemanding task conditions. However, as task demands increased, visual P300 was reduced in the dyslexic men as compared with the normal readers. An Abbreviated Conners Parent Rating Scale was used to assess retrospectively childhood symptoms of attention-deficit hyperactivity disorder (ADHD). Additional analyses revealed that the dyslexics with a history of many symptoms of ADHD in childhood (high ADHD) accounted for the group differences in P300; the dyslexics with a history of few or no such symptoms (low ADHD) were indistinguishable from the controls at all electrode sites. Furthermore, whereas the low-ADHD dyslexics showed the same hemispheric asymmetry in auditory P300 as did the controls (right > left), auditory P300 was more symmetrically distributed in the high-ADHD dyslexics. The results are interpreted as suggesting that a distinct brain organization may characterize dyslexic men with a history of concomitant deficits in attention.