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Stephen R. Arnott, Lore Thaler, Melvyn A. Goodale; Human Echolocation II. Journal of Vision 2010;10(7):1055. doi: 10.1167/10.7.1055.
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© ARVO (1962-2015); The Authors (2016-present)
Here we report fMRI data that reveal the neural substrates underlying the echolocation abilities of two blind individuals (aged 27 and 45 years) (see also Abstract ‘Human Echolocation I’). A passive listening paradigm was employed in all fMRI experiments. Using fMRI, we found increased BOLD signal in auditory and visual cortices in both persons in response to the presentation of sounds. Remarkably, however, a contrast analysis, applied to the whole brain, revealed that the BOLD signal in ‘visual’ cortex increased during the presentation of echolocation sounds as compared to spectrally matched control sounds, while the BOLD signal in auditory cortex remained unchanged. Furthermore, a region-of-interest analysis of visual cortex suggested that the processing of echoes reflected from objects placed to the left or right of the head were associated with increased activity in the contralateral occipital cortex. Finally, when our two participants were instructed to judge either the shape (concave vs. flat) or the location (right vs. left) of a sound reflecting surface, a contrast analysis applied to the whole brain revealed a stronger BOLD signal in ventral occipital areas during the shape judgment task. Importantly, the sounds that had been used in the shape and location tasks were the same. In their entirety, the results suggest that the echolocation abilities in our two blind participants appear to make use of the functional and topographic organization of visual cortex.
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