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Karl Zipser, Kendrick Kay, Amrita Puri; Visualizing allocation of attention in naturalistic scenes: an fMRI p-imaging study of human early visual cortex. Journal of Vision 2016;16(12):870. doi: 10.1167/16.12.870.
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© ARVO (1962-2015); The Authors (2016-present)
How flexibly can visual attention modulate retinotopic cortical representations of complex scenes? To address this question, fMRI scanning of early visual cortex was conducted as three fixating subjects viewed naturalistic images. For each image, subjects were instructed to attend to distinct scene elements during separate presentations. As a control, subjects were instructed to read small and rapidly presented letters appearing at fixation under the same conditions. A technique called p-imaging was employed to project functional activity measurements onto the image space in order to visualize how the allocation of attention modulates BOLD signals. Relative to the reading control, allocation of attention to different scene elements yielded positive modulation of BOLD signals at corresponding locations in the p-images. The magnitude of this modulation was comparable to that which could be explained by low-level image features such as textures and edges. The shape and position of attentional modulation revealed in p-images closely corresponded to the spatial extent of the attended objects. Attention to a relatively small peripheral face or other object elicited focused modulation. In contrast, allocation of attention to specific locations in featureless background parts of scenes resulted in spatially diffuse positive modulation within these areas. When attention was differentially allocated to broad complementary scene regions -- figure vs. background in realistic scenes, or different figure-ground interpretations in ambiguous synthetic scenes -- differential modulation was sufficiently pronounced and widespread across the visual field so as to yield highly uncorrelated p-images. These results show that the different subjective experiences related to different ways of allocating attention correspond to highly specific patterns of BOLD signals in early visual cortex, and suggest that the potential for attentional modulation increases with the richness of scene content.
Meeting abstract presented at VSS 2016
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