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Elizabeth Huber, Jessica M. Thomas, Ione Fine; Using the population receptive field method to assess auditory frequency tuning in early blind individuals. Journal of Vision 2013;13(9):888. doi: 10.1167/13.9.888.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction: Individuals with early onset blindness have enhanced auditory abilities that are associated with changes in both auditory and occipital cortex. In auditory cortex, alterations of the amplitude and extent of responses have been noted (Elbert et al. 2002; Stevens and Weaver, 2009). In occipital cortex, early blind subjects show cross-modal responses to a wide range of auditory stimuli across multiple visual areas (Roder et al., 2002; Poirier et al., 2005; Lewis et al., 2010). Methods: We carried out tonotopic mapping in auditory and occipital cortex in 4 early blind and 4 sighted controls using functional magnetic resonance imaging. Our stimuli were pure tones ranging from 88 to 8000 Hz, presented in ascending, descending, and randomized sequences during separate runs, based on methods used by De Costa et al. (2011). Data were analyzed using an adaptation of the population receptive field technique developed by Dumoulin and Wandell (2008) for retinotopic mapping. Our model treats the aggregate receptive field underlying each voxel's response as a one-dimensional Gaussian function of frequency. This technique provides an estimated sensitivity function for each voxel with a given center, or preferred frequency, and standard deviation, or tuning bandwidth. Results: We obtained consistent and reliable tonotopic maps within auditory cortex for both subject groups. It remains to be determined with additional subjects whether tuning bandwidth and/or the size of PAC might differ across blind and sighted subjects. We also observed cross-modal responses to pure tones in early blind, but not sighted, subjects. These frequency selective responses to pure tones in occipital cortex of blind subjects were as robust as PAC responses. In contrast to responses in PAC, the majority of occipital responses were preferentially tuned to frequencies within a 1000-1500 Hz range. This range is associated with a variety of behaviorally relevant sounds.
Meeting abstract presented at VSS 2013
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