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Elizabeth Huber, Jessica Thomas, Ione Fine; Enhanced cortical representation of auditory frequency as a result of early blindness. Journal of Vision 2014;14(10):1135. doi: 10.1167/14.10.1135.
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© ARVO (1962-2015); The Authors (2016-present)
A fundamental ability found to be enhanced by early blindness is frequency discrimination; however, the neural basis of this enhancement is unclear. Responses to a variety of auditory stimuli have been found throughout occipital cortex, but clear evidence for frequency tuning has not been reported. In auditory cortex, attenuated responses to pure tones have been found in early blind and anophthalmic individuals (Stevens and Weaver, 2009; Watkins et al., 2013). Here, we measured responses to pure tones in 5 early-blind and 5 age-matched sighted subjects to assess group differences in the organization of auditory frequency representations within occipital and auditory cortex. Methods: Stimuli consisted of pure tones ranging from 88 to 8000 Hz, which were presented in partially randomized order while subjects performed a 1-back frequency matching task. Data were analyzed using an adaptation of the population receptive field technique (Dumoulin and Wandell, 2008). We modeled the aggregate receptive field underlying each voxel's response as a one-dimensional Gaussian function of frequency, with a center and standard deviation that reflect preferred frequency and tuning bandwidth, respectively. Results: Within auditory cortex, we could reliably measure individual tonotopic maps in both subject groups, and we saw no evidence for an attenuation of responses. Relative to controls, early-blind subjects showed an enhanced representation of low to middle frequencies (<4 kHz) and narrower tuning bandwidths. In occipital cortex, blind but not sighted subjects showed evidence of auditory frequency tuning. Frequency tuned voxels in occipital cortex favored the mid-frequency range (1-8 kHz) and had narrower bandwidths then those found in auditory cortex. Conclusions: Early blindness results in an increased cortical representation of behaviorally relevant frequencies within both auditory and occipital cortex. Future work will examine how responses in these cortical areas relate to frequency discrimination performance in individual subjects.
Meeting abstract presented at VSS 2014
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