Listeners can rapidly adjust how they localize auditory stimuli when consistently trained with spatially discrepant visual feedback. However, relatively little is known about what auditory processing stages are altered by adaptation or the mechanisms that cause the observed perceptual and behavioral changes. Experiments were conducted to test how spatial adaptation generalizes to novel frequencies and the degree to which perceptual recalibration and cognitive adjustment contribute to spatial adaptation. A neural network model was developed to help explain and predict behavioral results. Adaptation was found to generalize across frequency when both training and reference stimuli were dominated by interaural time differences (ITDs), but not when the training stimuli were dominated by interaural level difference (ILDs) and the reference stimuli were dominated by ITDs. These results suggest that spatial adaptation occurs after ITDs are integrated across frequency, but before ITDs and ILDs are integrated. Both perceptual and cognitive changes were found to contribute to short-term auditory adaptation. However, their relative contributions to adaptation depended on the form of the rearrangement of auditory space. For both a magnification and a rotation of auditory space, at least some of the adaptation comes from perceptual recalibration. However, for a magnification of auditory space, cognitive adjustment contributed less to the observed adaptation than for a rotation of auditory space. A hierarchical, supervised-learning model of short-term spatial perceptual, recalibration was developed. Discrepancies between the perceived and correct locations drive learning by adjusting how auditory inputs map to exocentric locations to reduce error. Learning affects locations near the input location through a spatial kernel with limited extent. Model results fit the observed evolution of localization errors and account for individual differences by adjusting only three model parameters: the internal sensory noise, the width of the spatial learning kernel, and the threshold for detecting an error. Results demonstrate how training helps listeners calibrate spatial auditory perception. This work can help inform the design of hearing aids and hearing-protection devices to ensure that listeners receive sufficient information to localize sounds accurately, despite distortions of auditory cues caused by these devices.
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/45101 |
| Date | January 2009 |
| Creators | Lin, I-Fan |
| Publisher | Boston University |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
| Rights | This work is being made available in OpenBU by permission of its author, and is available for research purposes only. All rights are reserved to the author. |
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