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Research by Karen Froud and Reem Khamis-Dakwar Accepted by American Journal of Speech Language Pathology (AJSLP)

MisMatch Negativity Responses in children with a diagnosis of Childhood Apraxia of Speech (CAS)

Karen Froud
Teachers College, Columbia University

Reem Khamis-Dakwar
Adelphi University

Purpose: The underlying deficit in Apraxia of Speech is a debated topic, and it remains unclear whether distinctions exist between causal mechanisms involved in developmental versus acquired apraxia. One proposal suggests that apraxia of speech results from phonological over-specification (Dogil, Mayer, & Vollmer, 1996). To evaluate whether this hypothesis could be relevant for Childhood Apraxia of Speech (CAS), we investigated brain responses to auditorily-presented phonemic and allophonic speech sound contrasts, in children with CAS compared to typically-developing (TD) peers.

Method: High-density EEG was recorded from 5 children with CAS and 5 matched controls, aged 5–8 years, with and without CAS, as they listened to randomized sequences of CV syllables in two oddball paradigms: phonemic (/ba/, /pa/) and allophonic (/pa/, /pha/).

Results: In the phonemic contrast condition, mismatch negativity (MMN) responses to oddball sounds were observed for the TD group but not the CAS group, although a component similar to an immature mismatch response was apparent. The allophonic contrast did not elicit MMN responses in the comparison group, but in the CAS group an MMN-like response was observed.

Conclusions: We propose that these preliminary findings are consistent with a view of CAS as a disorder that affects not only motor planning, but also has a phonological component.

AJSLP Papers in Press
Published online May 7, 2012
American Journal of Speech-Language Pathology 2012; doi:10.1044/1058-0360(2012/11-0003)

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