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Stephen Arnott, Lore Thaler, Jennifer Milne, Daniel Kish, Melvyn Goodale; Functional imaging of shape processing in a blind echolocation expert. Journal of Vision 2012;12(9):580. doi: 10.1167/12.9.580.
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We have previously reported that an early-blind echolocating individual showed robust occipital activation when he identified distant, silent objects based on the auditory information attained through echoes from his tongue clicks (Thaler, Arnott & Goodale, 2011, PLoS ONE, 6(5), e20162). In the present echolocation study, we investigated the extent to which the occipital activation reflected general auditory processing per se, as well as whether object feature processing recruited specific occipital regions. As in our previous study, binaural sound recordings were made as the participant stood in front of objects (i.e., a concave-facing bowl or a flat disc of the same diameter) and emitted echolocation clicks. Each object’s surface was covered in either aluminium foil or a thin cotton-towel and each of the recordings was made in an anechoic chamber and again in a small reverberant alcove. All eight auditory stimuli (2 shapes x 2 surface compositions x 2 environments) were then randomly presented to the participant during a sparse-temporal scanning fMRI session in which the participant was asked to discern either the object’s shape or surface, or to determine which environment the recording had occurred in. Relative to shape or surface composition judgments, whole-brain voxelwise analyses revealed that environment judgments strongly activated the right calcarine cortex, suggesting involvement of this area in general auditory processing. Interestingly, even though the participant was listening to the same stimulus set, discerning the object’s shape preferentially activated the left occipital pole and angular gyrus to a greater extent than surface judgments. These shape-specific activations were slightly increased for the chamber compared to the more difficult alcove trials, arguing against a mere effect of task difficulty. Together, our results reaffirm this expert’s use of the occipital lobe to accomplish echolocation, demonstrating the specific involvement of the left occipital pole in this particular shape processing task.
Meeting abstract presented at VSS 2012
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