Determining the mechanisms of spoken language processing delay for children with cochlear implants

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Project Summary While cochlear implants (CIs) have enabled children with profound hearing loss to hear via an electrical signal, the speech signal they transmit is degraded in ways that hinder speech perception. These difficulties with speech perception likely have downstream consequences on development, as children with CIs are more likely to show delays in speech, language, and literacy abilities relative to peers with NH. However, it is unclear how CI-specific limitations in speech perception contribute to observed delays in spoken language processing. The long-term objective of this project is to better understand how the degraded CI signal impacts spoken language development in children with CIs in order to design more targeted and efficacious intervention for this population. The specific objective of the proposed research is to utilize psycholinguistic methods to investigate how the spectrally degraded speech signal transmitted by CIs delays spoken word recognition and the access of networks of semantically related words in the lexicon, which are both vital components for efficient spoken language comprehension. Aim 1 will investigate the potential sources of observed delays in spoken word recognition by children with CIs. Specifically, the proposed experiments will determine whether perception of a spectrally degraded signal leads to expanded and less efficient lexical competition or adoption of a general wait-and-see listening strategy. The applicant will use eye- tracking to measure competition from similar-sounding words while children with CIs (Experiment 1) and children with NH listening to noise-vocoded speech (Experiment 2) perceive spoken words. Experiment 3 will use electroencephalography (EEG) to measure semantic processing of phonologically similar words during spoken word recognition. Aim 2 will investigate the possible mechanisms underlying observed delays in use of semantic context by children with CIs to facilitate spoken language processing. The team will determine whether lexical access by children with CIs involves cascading activation from phonological to semantic networks or instead occurs as a more serial process. Experiment 4 will use EEG to measure how similar-sounding words and their semantic associates are activated during spoken word recognition. Training goals focus on learning to use EEG methods for psycholinguistic research, manipulation of speech stimuli, and advanced statistical analysis of time series data. In addition, training will foster skills needed to independently carry out innovative and clinically applicable research by incorporating findings from the field of cognitive neuroscience and collaborating with clinical faculty and local clinicians. The findings from the proposed project will contribute to a more detailed understanding of the mechanisms behind observed delays in spoken language processing by children with CIs. Processing mechanisms yielding individual differences in spoken word recognition also have the potential to be targets of speech-language intervention for children with CIs who are at-risk of falling behind in language development.