Symposium: Clinical applications: hearing and speech disorders
Wednesday, Sep 9, 2015
Vowel length and stress pattern discrimination in young children with cochlear implants
Sächsisches Cochlear Implant Center, Universitätsklinikum Dresden, Dresden, Germany
Cochlear implantation restores hearing in congenitally deaf children with the prospect of oral language acquisition. Only scarce knowledge exists, however, of what these children actually perceive, when receiving their first auditory input and specifically what speech relevant features they are able to extract from the new modality.
We presented congenitally deaf infants and young children implanted before the age of four with an oddball paradigm of either (a) long and short vowel variants of the syllable /ba/ or (b) bisyllabic items with stress either on the first or on the second syllable (/báaba/ vs. /babáa/). We measured the EEG in regular intervals to study their discriminative ability starting with the first activation of the implant up to six months later. We were thus able to time-track the emerging ability to differentiate two of the most basic linguistic features that help in word segmentation, namely vowel length and stress pattern. Results show that already two months after the first auditory input, but not directly after implant activation, these early implanted children differentiate between long and short syllables. Surprisingly, after only four months of hearing experience the ERPs have reached the same properties as those of the normal hearing control group. A similar development is seen for the stress pattern contrast. We thus show that simple but linguistically highly relevant features reach age-appropriate electrophysiological levels within the first months after the initial acoustic stimulation, providing good ground for further language acquisition.