FMRI OF AUDITORY ATTENTION TO COMPLEX ENVIRONMENTAL SOUNDS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The overall goal of this study is to provide a better understanding of the organization and mechanism of human cortical systems involved in aspects of both environmental sound recognition and in sound localization in 3-dimensional space. To achieve this goal, functional magnetic resonance imaging (fMRI) will be used to differentiate, map and functionally characterize brain regions (in both sighted and blind people) involved in directing attention to three-dimensionally (3D) localizable natural sounds, presented over a high fidelity headphone system while participants are lying in the MRI scanner. Emphasis will be placed on (1) mapping cortical pathways preferential for processing the spatial location ("where") versus recognizing the content of the complex natural sounds ("what"). We expect to activate a specific "fronto-parietal" network during spatial attention to sound, and several high-level, auditory-association regions during attention to the content of that same sound stimulus. Due to our recent discovery of partially separate pathways in cortex for processing animal vocalizations relative to hand-manipulated tool sounds (two distinct conceptual categories of sound), we will also determine (2) if activity along these distinct pathways can be modulated by attention. This will be assessed by presenting simultaneous sound-sources, requiring the participant to ignore the distracting sound(s). We will additionally be able to determine if portions of the fronto-parietal cortical network (mentioned above), are also involved in "auditory streaming", wherein attention is directed to processing one sound-source, having to filter out the other(s). Volunteer participants will perform auditory behavioral tasks while functional images are acquired with a newly upgraded 3 Tesla General Electric Horizon HD scanner research scanner, using echo-planar and/or spiral imaging sequences for T2* weighted functional images. We will use a "silent" clustered acquisition fMRI paradigm (event-related), which is designed to allow high fidelity sound to be delivered directly to the ears (under ear muffs) during silent periods of the scanning process, thereby minimizing or eliminating interference associated with scanner noise. Together, the experiments in this project seek to identify cortical systems responsible for sound recognition, spatial localization, and auditory attention, providing detailed maps of both distinct and overlapping cortical pathways responsible for our perception of the different types of information contained in complex natural sounds. The results will significantly advance the body of knowledge pertaining to human auditory processing.