SPEECH UNDERSTANDING UNDER NON-OPTIMAL CONDITIONS AGING

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The proposed research is focused on one particularly disturbing auditory communication deficit, namely, the often markedly reduced ability of elderly individuals to understand speech under non-optimal listening conditions, such as in social settings with several simultaneously ongoing conversations or in reverberating rooms. This deficit, often referred to as the loss of the "cocktail-party" effect in aging, has been the focus of an increasing number of investigations for the last 25 years; yet, present-day understanding of the deficit is still incomplete. Our previous research has identified several components of this deficit; those that were not connected to hearing loss were related to spatial processing as well as temporal processing both in the syllabic and segmental time ranges. The proposed study will have two specific objectives: (1) investigate, in elderly and young individuals, certain specific functions responsible for temporal analysis of auditory signals, and identify those that, when impaired, are correlated with age-related deficits of speech understanding under non-optimal listening conditions, and (2) over a five-year period, determine the extent to which a decline in speech understanding under non- optimal listening conditions in elderly individuals can be predicted from the deterioration of general audiological abilities and/or specific auditory temporal processing functions. Significance of the project lies in that it will provide data that may explain why some elderly individuals are able to understand speech in interference while others are not. It will also throw light on segmental and suprasegmental aspects of the segregation of speech from interference and supply information on the multidimensional profile of the age-related decline in speech understanding and its connection to temporal processing. In doing so, it is likely to supply data useful for the development of next-generation hearing aids able to help people understand speech where presently available amplifying hearing aids do not. The study will consist of three parts. Part I will assess the age-related audiological and auditory status, including speech processing and temporal processing, in a large group of elderly individuals, and serve as a subject selection stage for the other two parts. Part II will investigate segregation of nonspeech signals differing in well specified temporal and spectral attributes. Part III will follow groups of elderly subjects over a five-year period and monitor the pattern and the rate of decline of functions that enable speech understanding and temporal processing amidst interference.