Separate brain potential characteristics in children with reading disability and attention deficit disorder: color and letter relevance effects.

This experiment was on event-related potential (ERP) indicants of the selective neural processing of black vs. white and letter vs. nonletter stimuli in boys (8-12 years of age) with and without a reading disability (RD) and/or attentional deficit disorder (ADD). Selective neural processing was measured by the increase or difference in ERP amplitude in response to stimuli that were relevant as compared to irrelevant to the color or letter attention task. The 52 children that participated in the study constituted four groups: 25 normal reading children (17 without ADD and 8 with ADD), and 27 RD children (11 without ADD and 16 with ADD). ERPs were recorded over the left and right occipital, central, and frontal regions. Selective neural processing due to stimulus relevance was reduced in boys with RD as compared to normal readers. This reduced selectivity was indicated by a predominantly symmetrical reduction in the magnitude of a positive difference potential over the central regions, between 300 and 360 msec, and then by a left greater than right hemisphere reduction in the magnitude of a positive difference potential over the occipital regions, at about 400 msec. Task relevance increased the within-subject and condition variability of this occipital positive component and this effect was greater for boys without than with RD, particularly over the left hemisphere. Selective neural processing due to stimulus relevance was greater in boys with ADD as compared to those without ADD. This was indicated by an increase in the magnitude of a positive difference potential between 320 and 400 msec over the central and frontal regions and a slow, late, negative difference potential between 600 and 800 msec over the central and occipital regions. These ADD effects tended to be greater over the right than left hemisphere. The unique polarity, scalp distribution, and time course of the effects of RD as compared to ADD on ERPs to relevant stimuli clearly indicated these two disorders, in part, involve different underlying brain deficits.