The purpose of this research is to investigate monaural auditory temporal processing new psychophysical data with quantitative model predictions. The project has three main aims: (i) To investigate the influence of peripheral (cochlear) non-linearities on psychophysical measures of temporal resolution; (ii) to examine the consequences of a loss of non-linearity due to sensorineural hearing loss; and (iii) to functionally characterize higher stages of temporal processing. Two experiments will examine the magnitude and the time course of psychophysical suppression to discover the extent of which physiological and psychophysical suppression are reflections of the same underlying process. The results will clarify the role of suppression in certain measures of temporal resolution. Further experiments will test the hypothesis that the non-linear growth of forward masking is a reflection of peripheral non-linearities and that more central processes can be treated as quasi linear. Results from normal-hearing listeners will be compared with those from listeners with moderate-to severe cochlear hearing loss to test whether the differences can be accounted for solely by the expected changes in peripheral compression. The hypothesis, if supported, will have important consequences for the modeling and understanding of temporal resolution in hearing-impaired listeners. The penultimate experiments will seek to elucidate the underlying mechanisms of forward masking comparing predictions of the two most popular theories, namely adaptation of response and persistence (or integration) of response, with experimental data designed to distinguish between the two. The final experiment will examine how information is combined across frequency in a forward-masking situation. An understanding of the changes in temporal resolution due to hearing impairment may ultimately assist in selecting appropriate parameters for the design of digital hearing aids.
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