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Abstract:
Using Positron Emission Tomography, we investigated the
neural substrate underlying speech comprehension in post-lingually
deaf rehabilitated cochlear implant patients listening to sentences
in their native language (L1, French). At the same level of
intelligibility (100%), brain regions specialized for speech
comprehension were more activated in a group of 6 patients than in
a control sample of 6 normal-hearing subjects. We also demonstrated
that part of this network was more active in healthy subjects (low
proficiency bilinguals) when they listened to sentences in their
second language (L2, English) compared to their native language.
The search for activations common to the processing of L1 in
implant patients and the processing of L2 (but not L1) in low
proficiency bilinguals allowed us to show for the first time that,
although second and native languages engage exactly the same speech
comprehension system, L2 activates some phonological and acoustic
cortical regions and auditory subcortical regions more than L1.
These activations appear to reflect the use of speech comprehension
strategies for unusual speech sounds rather than being specific to
second language processing.
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