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Abstract:
We employed a rhyming experiment to investigate the
development of the brain systems important in phonological
processing. In studies of adults, Rugg and colleagues (Rugg,
1984a,b; Barrett & Rugg, 1990) described two main components: a
negative slow wave to "primes" that preceded target presentation
that was larger over anterior regions of the left hemisphere, and a
negative deflection (N400-450) largest from right temporal-parietal
regions that was larger for nonrhyming than rhyming words (mismatch
effect). In this experiment we studied 109 right-handed, native
English speakers within the following age groups: 7-8, 9-10, 11-12,
13-14, 15-16, 17-18, 19-20, 21-23. Participants had to decide
whether two written words rhymed (nail-male) or not (NAIL-SIGN).
The asymmetry of the response to primes (left anterior regions more
negative) increased with age, perhaps indexing an enhanced role of
these areas in articulation and subvocal rehearsal of phonological
information, as has been found in PET studies of adults (Paulesu et
al., 1993; Shaywitz et al., 1995). The overall amplitude of the
N400-450 and the mismatch effect decreased with age; however, the
distribution (largest from right temporal-parietal) was stable,
suggesting similar cerebral systems are employed across these ages.
The latency of the N400-450 did not change with age; by contrast,
the following P300, reaction times and accuracy did vary with age.
In addition, the mismatch effect was highly variable and not
significant in the youngest group. This suggests that the areas
involved in phonological matching continue to become organized over
a prolonged timecourse during development.
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