This R03 application is to support a preliminary investigation of age-related differences in the neurocognitive mechanisms associated with speech recognition under conditions that simulate listening through a cochlear implant (Cl). There is considerable variability in speech recognition abilities of adult and, in particular, pediatric Cl users. Part of this variability may result from suboptimal fitting of the internal parameters of the Cl or variable functional integrity of the ascending auditory pathway of individual patients - both of which may lead to distortions or reduction of the acoustic input; however, patients also differ in important ways of how they deploy their neurocognitive processes to compensate for such acoustic distortions in order to maximize their speech recognition performance. Better characterization of these neurocognitive processes is critical for a more accurate assessment of the potential benefits of Cl as implantation criteria are expanded to include more individuals with different types of sensory and/or neurocognitive impairments in addition to their hearing loss. Functional magnetic resonance imaging (fMRI) is a powerful neuroimaging tool that can provide information about neurocognitive functions with high spatial resolution; it can be performed in children and adults in the absence of ionizing radiation. Recent advances in imaging technologies allow us to present speech stimuli in the relative absence of the intense noise generated by the magnet's gradients while collecting data in a time-efficient manner.
The specific aim of this application constitutes a prerequisite step that must be addressed in order to fully characterize the neural correlates of speech recognition in Cl users. Specifically, we propose to use fMRI to contrast brain activation patterns elicited by natural speech versus speech with acoustic distortions that mimic those of a Cl (i.e., vocoded speech), in children and late adolescents with normal hearing (NH). These data should reveal the neurocognitive processes normally recruited to decode acoustically degraded speech and how such processes change with age. The results may also lead to a better understanding of the performance variability among pediatric Cl users and further development of fMRI to provide useful clinical information in the Cl evaluation process.
