Maturational changes in ERPs to orthographic and phonological tasks

Children from 7 to 18 years of age (divided into 2 year groupings, i.e., 7-8, 9-10, etc.) and young adults were studied (total of 84 subjects). ERPs were recorded from 19 electrodes during 2 visual oddball tasks: an orthographic task requiring responses to letters with a closed loop (e.g., a, p), and a phonological task, requiring responses to letters that rhymed with 'v' (e.g., c, p). N2 and P3 peak latencies and amplitudes were measured on the difference potentials. RTs decreased with age and between tasks (orth < phon). N2 and P3 latencies decreased with age and were shorter for the orthographic than phonological task. P3 amplitude was lower for the phonological task; the cortical distribution varied significantly as a function of age and task. The task differences in distribution were more marked in the younger age groups. Hemispheric asymmetries in P3 amplitudes were seen in the phonological task. The orthographic task required simple visual feature recognition and the phonological task required a visual-to-auditory translation. The interaction effects suggest that cortical utilization differs for these tasks, with greater age-related changes for the phonological task.