ERP correlates of form and rhyme letter tasks in impaired reading children: a critical evaluation.

Event-related potentials (ERPs) were obtained from 15 electrode sites in six average and six impaired reading children, 12 years of age, during visual letter discrimination tasks. Subjects responded to target letters with an enclosed area in the form task and to letters that rhymed with "e" in the rhyme task. Response accuracy was similar between the groups. Reaction time was relatively longer for the impaired group during the rhyme task. At lateral sites, condition differences were evident as greater negative shifts in the rhyme task than the form at 170 and 470 ms as well as a delayed late positivity for the rhyme. In terms of reading ability, the average readers' ERPs were more negative than those of the impaired group at 270 and 450 ms. Inter-hemispheric variations were also seen between the groups, with the average readers more negative than the impaired readers at right hemisphere sites. Contrary to expectations, group differences in the ERP did not vary substantially as a function of condition, and task demands were evaluated in view of these findings.