| Abstract: | This investigation compared the visual evoked responses (VERs) and reaction time (RT) performance of 24 dyslexic boys and 24 controls at four different age levels (7, 9, 11, and 13 yrs). Prescreening and matching techniques were used to eliminate differences due to social or educational deprivation, gross sensory-motor handicaps, specific neurological deficiencies, or intellectual impairment. The VER was recorded from four scalp locations (O1, O2, P3, and P4) referenced to the vertex during a detection task in which subjects were required to respond to dim flashes occurring in a train of brighter flashes. An overall hemispheric asymmetry in VER amplitude (right > left) was observed in both experimental and control subjects. Dyslexics exhibited an increased amplitude to unattended stimuli and a slower RT to attended stimuli. Normals exhibited significant correlations between RT and VER latency, dyslexics did not. There were no significant VER-IQ correlations. The results are discussed in terms of an attentional deficit hypothesis. |
