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Valentinos Zachariou, Nikas V. Christine, Leslie G. Ungerleider; Dorsal Stream Contribution to Perceiving the Structure of Objects. Journal of Vision 2014;14(10):1297. doi: 10.1167/14.10.1297.
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Growing evidence suggests that the functional specialization of the two cortical visual pathways may not be as distinct as originally proposed (Konen & Kastner, 2008; Kravitz, Kriegeskorte & Baker, 2010). Specifically, mechanisms that process the spatial position of objects may also contribute to some aspects of shape perception (Zachariou et al, 2013). This common resource could arise because changes in an object's shape alter location as well, but with respect to the object's parts rather than with respect to other objects. By such an account, perceiving the structure (i.e. shape) of an object, defined as the spatial arrangement of the parts that constitute the object, requires the analysis of location and, hence, dorsal stream processing. Here, we explore this hypothesis in healthy human volunteers who performed a shape-change detection task on two object categories (faces and chairs) while undergoing functional magnetic resonance imaging (fMRI). In each category, two exemplars presented simultaneously on a screen could differ in terms of the shape of their constituent parts (featural differences) or the spatial configuration of their parts (configural differences). For both the face and chair categories, configural differences led to significantly stronger activation within the dorsal visual pathway compared to featural differences. Additionally, the magnitude of this activation correlated with behavioral performance. The dorsal visual pathway was a-priori localized using an independent localizer task. This dorsal activation profile in response to configural differences is particularly noteworthy given that: 1) the visual input was identical for the featural and configural difference stimuli of each category; and 2) the tasks were matched for difficulty. We conclude that the dorsal visual pathway processes the spatial arrangement of elements that constitute the structure of objects and, through this mechanism, contributes to shape perception.
Meeting abstract presented at VSS 2014
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