MICHAEL ASHBY & JOHN MAIDMENT, Introducing Phonetic Science (Introductions to Language and Linguistics). Cambridge: Cambridge University Press, 2005. Pp. 230. ISBN: 0-52-1004969 (pbk) - - Volume 36 Issue 1 - David M. Howard

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  • Rita Ceponiene
  • Paavo Alku
  • Marissa Westerfield Marissa Westerfield
  • Jeanne Townsend

We examined maturation of speech-sound-related indices of auditory event-related brain potentials (ERPs). ERPs were elicited by syllables and nonphonetic correlates in children and adults. Compared with syllables, nonphonetic stimuli elicited larger N1 and P2 in adults and P1 in children. Because the nonphonetics were more perceptually salient, this N1 effect was consistent with known N1 sensitivity to sound onset features. Based on stimulus dependence and independent component structure, children's P1 appeared to contain overlapping P2-like activity. In both subject groups, syllables elicited larger N2/N4 peaks. This might reflect sound content feature processing, more extensive for speech than nonspeech sounds. Therefore, sound detection mechanisms (N1, P2) still develop whereas sound content processing (N2, N4) is largely mature during mid-childhood; in children and adults, speech sounds are processed more extensively than nonspeech sounds 200–400 ms poststimulus.

Ample evidence suggests that developmental dyslexia results from a phonological deficit that may not be reducible to a low-level auditory deficit. Yet, on-line phonological processing (in)capacities in dyslexics remain virtually unexplored, as studies have typically focused on either meta-phonological awareness tasks or, at the other extreme, basic perceptual tasks. The present study investigates event-related potential (ERP) correlates of implicit phonological processing during the recognition of spoken words in dyslexic and normally reading children (7-10 years). We examined general ERP morphology and alliteration priming effects on ERP measures in an auditory lexical decision task. Primes were words (Experiment 1) and non-words (Experiment 2). Alliteration priming effects suggested a distinct pattern of normal versus anomalous aspects of spoken word processing in dyslexic children. Whereas dyslexics showed deviant priming effects in earlier time windows encompassing the N1 and N2, later N400 priming effects were comparable to those of normal readers. The same pattern of results was also present in group comparisons of general ERP morphology. These findings suggest that dyslexics have selective processing anomalies at an earlier phonetic/phonological level, while processing at a later phonological/lexical level proceeds normally. In particular, our results indicate an anomalous contribution of phonological (word onset) information to the processing of spoken words, which may be related to time-course aspects of phonetic/phonological processing.

We investigated event-related potential (ERP) correlates of developmental changes in spoken word recognition during early school years. We focused on implicit processing of word onsets as this may change considerably due to vocabulary growth and reading acquisition. Subjects were pre-schoolers (5-6 years), beginning readers (7-8 years) and adults. Two experiments examined phonological onset priming effects on ERP measures in an auditory lexical decision task. Primes were words (Expt. 1) or non-words (Expt. 2). ERPs elicited by words showed clear developmental changes in ERP latency and morphology, especially with regard to early negativities like the N1. Prominent priming effects were an enhanced N400 amplitude due to alliterating word primes in beginning readers, and typical phonological N400 reductions due to alliterating non-word primes in all groups. Priming further led to opposite early effects with word primes (N1/N(200) reduction) vs. non-word primes (P1/N1 enhancement) in all groups. These changes in ERP morphology and priming effects suggest that the lexical system undergoes substantial restructuring at the level of phonological processing and representation. In particular, our results indicate distinct processing of word onsets in beginning readers, confirming that vocabulary growth and the acquisition of reading may critically contribute to the formation of a fully segmental lexical system.