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Maryam Vaziri-Pashkam, Yaoda Xu; Object Representations In Human Parietal And Occipito-Temporal Cortices: Similarities And Differences. Journal of Vision 2015;15(12):374. doi: https://doi.org/10.1167/15.12.374.
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© ARVO (1962-2015); The Authors (2016-present)
Although visual objects are largely represented in the primate occipital and temporal cortices, many studies have also documented the existence of object representations in the primate parietal cortex. What are the characteristics of the parietal object representations? And how do they differ from those in occipital and temporal cortices? Here, using fMRI multi-voxel pattern analysis, we examined object representations in human observers in topographically defined parietal regions (IPS0-IPS4) and two functionally defined parietal regions previously implicated in object processing, namely, superior and inferior IPS. To compare and contrast, we also examined topographic regions in occipital cortex (V1-V4) and object shape selective regions in lateral occipital and ventral temporal cortices. Observers viewed objects from eight categories and performed a one-back repetition detection task. In the first set of studies, we varied the position, size and spatial frequency of the object images, and whether or not image luminance and spatial frequency were matched across the categories. We obtained significant object category decoding in all the regions examined. Importantly, parietal regions showed similar tolerance to changes in low-level features as occipital and temporal regions (excluding early visual areas). However, when we compared object category similarity measures across brain regions, we found that parietal object representations were not a mere copy of those in occipital and temporal regions. In a second set of studies, we varied the task and found that, when attention was diverted away from the objects, although category decoding was still significant in occipital and temporal regions, it was no longer significant in multiple parietal regions. Overall these results show that, just like regions in occipital and temporal cortices, high-level object representations exist in human parietal cortex; however, they are distinct from those in occipital and temporal regions.
Meeting abstract presented at VSS 2015
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