A developmental study of visual ERP distributions during spatial and phonetic processing.

Ten adults (mean age 19.5 years; S.D. = 1.65) and 10 children (12.2 years; S.D. = 1.28) participated in a choice reaction time study of event-related potential (ERP) correlates of pattern and phonological discriminations of letters. In the form condition, the subjects responded discriminately to letters that did (e.g., b, p) and did not (e.g., f, h) have an enclosed area. Likewise, the subjects responded to letters that did and did not rhyme with "e" in the rhyme task. For both groups, the two late positivities (P600 and P3) were significantly later in the rhyme ERPs than the form as were the RTs associated with the tasks. Distribution and group differences were most notable for the positivity at 380 msec. The P380 distribution did not vary between the conditions for the adults, but there was a more negative distribution in the rhyme condition compared to the form at fronto-central sites for the children. The topographic differences between the form and rhyme tasks at 380 msec were consistent with the involvement of auditory areas in the rhyme task. Generally, however, the children's and adults' wave forms were similar in terms of morphology, peak latency and distribution.