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Olivia Cheung, Alfonso Caramazza; Contextual influences on object representations in the occipito-temporal cortex. Journal of Vision 2015;15(12):1169. doi: 10.1167/15.12.1169.
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© ARVO (1962-2015); The Authors (2016-present)
What are the factors that determine how objects are represented in the visual system? Apart from visual shape, conceptual information such as animacy and object size has been established as major organizational principles for object representations in the occipito-temporal cortex. However, it remains unclear whether object representations may also be influenced by contextual information (i.e., where objects appear in the world). There has been debate regarding whether contextual information is retrieved when objects are seen, and whether the neural locus of contextual effect may be in the object-selective lateral occipital complex (LOC) or the scene-selective parahippocampal cortex (PHC). We examined how object representations in the occipito-temporal cortex may be influenced by animacy, object size, and context. We used 24 items, including 4 animals, 4 big and 4 small inanimate objects for each of 2 contexts (e.g., beach items: dolphin, lifeguard chair, goggles; house items: dog, coffee table, vase). Sixteen exemplars were included for each item. Using fMRI, neural responses for the 24 items were obtained when participants (n=15) performed a one-back task to match identical images. To analyze the nature of object representations, we first calculated representational similarity matrices (RSMs) on the neural response patterns for the 24 items in both the LOC and the PHC (defined in a separate localizer). We then correlated the neural RSMs with several candidate models of RSMs. We found that a RSM that incorporated the effects of animacy, object size, and context was significantly correlated with the RSMs in both LOC and PHC. The correlations were stronger compared to those with other candidate RSMs, which concerned only animacy and size, or animacy alone. These results suggest that contextual information is engaged, even when such information is task-irrelevant. It appears that multiple sources of object knowledge contribute to form object representations in the occipito-temporal cortex.
Meeting abstract presented at VSS 2015
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