Sensory systems are continually challenged by the task of recognizing sources within a background of ambient noise. Research in sensory science should explain how this task is accomplished and identify stimuli that allow an animal to direct appropriate behaviors. The present study addresses this problem for two important detectors of vibratory sources--the inner ear and the closely related lateral line system of fishes. These closely related systems are proposed as a model of multi-sensory processing, for while the mammalian sense of hearing (in air) relies only on the detection of pressure fluctuations, most aquatic animals use multiple sensors to detect vibratory sources. These multiple systems provide information not only about the propagating pressure wave, but also two other aspects of the sound field surrounding a vibratory source: The acceleration field detected by inertial sensors of the inner ear; and the pattern of water motions detected by the lateral line. Thus each of these sensors responds to the same stimuli, but detects different physical aspects of the stimulus, and each has unique transduction mechanisms (the ways stimulus energy is transformed to neural activity). This study test hypotheses of how transduction mechanisms dictate the relevant aspect of the stimulus, which will increase our understanding of the biophysics of stimulus transduction in auditory systems. Further, this study will determine the ways in which multiple sensory systems are brought to bear in the perception of the natural environment. Unlike the majority of existing studies of these systems, which have been performed against a quiet background, this proposal measures the ability to detect spatially discrete signals and discriminate source location in both quiet and noisy settings. Another important feature of our experimental approach is the use of natural stimuli (vibratory dipoles rather than loudspeakers) that are effective for multiple hearing-related submodalities. This study is aimed at documenting and testing the ways multiple sensory systems combine to create unitary percepts in real-world situations. This research is important for the development of rehabilitation strategies following partial sensory loss and for the development of better sensory prostheses and automated sensors.
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