Within and Between Channel Representation

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DESCRIPTION (provided by applicant): This proposal constitutes a psychophysical experimental program which examines two aspects of auditory processing in the healthy human auditory system: (a) uncertainty-driven integration of information across frequency, and (b) observers' ability to detect and/or segregate target signals embedded in a background of distracters. The proposed experiments examine the integration of information across frequency and the integration of information across time and frequency, respectively. The primary goal of the first sequence of experiments is to compare effects of stimulus uncertainty using tasks in which observers should extract frequency from a single frequency locus vs. compare information across the spectrum. For the former task it has been suggested that observers fail to selectively attend to a single frequency locus, an explanation that is difficult to reconcile with uncertainty effects for the latter task. The second set of studies provides estimates of the relative efficacy of different cues for sound source segregation. The experiments examine the hypothesis that the multiple cues are independently represented and optimally combined. In addition, the experiments estimate frequency selectivity after the segregation of two sources into "auditory streams." The proposed experiments address these issues by analyzing threshold data and examining relative weights in time and frequency. Processing models associated with signal detection theory form the basis of data analysis. While the experimental observers are undergraduates with normal audiograms, the experimental methods can be adopted to test persons suffering hearing impairment, persons for whom the presence of multiple sources leads to substantial masking.