This proposal for an MCDSA requests support for a program of research on adult cochlear implant (CI) users. The long-term goal of this project is to obtain new knowledge about the underlying perceptual processes used in spoken work recognition in this clinical population. Specifically, this research focuses on the processes of perceptual normalization, lexical discrimination, auditory-visual integration and perceptual learning in listeners with CIs. We are also interested in how these perceptual processes are influenced by the type of signal processing strategy employed by the CIs. Comparisons will be carried out between the SPEAK strategy used in the Nucleus CI and the CIS strategy implemented in the Clarion CI. Research is also directed toward the study of individual differences in speech perception skills among CI listeners. The results of the four experiments on perceptual processing of spoken words will contribute new knowledge to current models of word recognition and provide a better understanding of the central auditory processes used by CI listeners. Experiment I on perceptual normalization deals with how listeners with CIs cope with different sources of stimulus variability due to difference in talkers, speaking rates, and speech styles. Experiment II, which is concerned with the process of lexical discrimination, focuses on how listeners with CIs make fine phonetic discriminating among acoustically similar words. Experiment III examines the use of multimodal information in speech perception and spoken work recognition and explores how listeners with CIs integrate visual and auditory speech inputs. Experiment IV examines the process of perceptual learning of novel voices and investigates how this information in the speech signal is used to recognize words in novel sentences. In addition to the proposed program of research with adult CI users, this application also describes a training component for the PI which involves attendance in formal classes and research seminars in Cognitive Psychology and Cognitive Science at Indiana University, Bloomington, as well as hands-on research training experience under a mentor's direction. The results of this research will provide new perceptual information that will be useful in the design of new CI speech processing strategies and auditory- perceptual training methods for aural rehabilitation with this clinical population. The findings from this research project also have theoretical implications for our current understanding of spoken language processing in both normal-hearing and hearing-impaired listeners and will help us to assess several recent claims surrounding the importance of encoding stimulus variability and the use of detailed episodic information in speech perception and spoken word recognition.
