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Christopher W. Tyler, Lora T. Likova, Alex R. Wade; Properties of Object Processing in Lateral Occipital Cortex. Journal of Vision 2004;4(8):91. doi: https://doi.org/10.1167/4.8.91.
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© ARVO (1962-2015); The Authors (2016-present)
Functional MRI (fMRI) studies of cortical activation by images of objects relative to scrambled versions of the same stimuli typically find that object-specific activity is centered on a region extending through the lateral occipital cortex (LOC), to the intraparietal sulcus dorsally and to the fusiform gyrus ventrally. By selective stimulus comparisons, we partitioned the properties of object responses into the components of: contour continuity, depth, symmetry, familiarity, and a joint factor of objectness in general. fMRI responses were recorded in a block design on a 3T GE Signa scanner with slices spanning the occipital lobes in six observers at a resolution of 3×3×3mm^3. The primary retinotopic areas responded more strongly to scrambled than intact objects (despite attempts to equate local contours) implying that the scrambled images contained more local contrast energy than the intact images. In comparison, the intact images tended to generate higher signal levels in LOC. In LOC as a whole, our comparisons revealed a patchwork of responses to the different component properties. Object depth generated responses in a region in dorsomedial LOC corresponding to the kinetic occipital (KO) area for motion-defined shapes, and in another area in the occipital part of IPS. Object symmetry activated regions in medial and ventral LOC near the human motion complex. Object familiarity activated distinct regions, ventrally near area V4v and dorsally near area V3A. Such feature-specific response segregation reveals that LOC is composed of identifiable sub-regions with topographic specialization for different aspects of object identity (within single object classes).
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