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Ruosi Wang, Yaoda Xu; Neural Preference for Vertical Symmetry. Journal of Vision 2013;13(9):1040. doi: 10.1167/13.9.1040.
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© ARVO (1962-2015); The Authors (2016-present)
Vertically symmetric patterns and designs are ubiquitous in our everyday lives and can be seen in the body plans of animals and the designs of manmade structures. Although both neurophysiological and neuroimaging studies have documented that mirror reversal objects and patterns are represented similarly in higher order visual object processing areas, a selective preference for vertically symmetric objects or patterns has not been directly observed. Cant and Xu (2012) recently showed that object ensemble processing involves anterior-medial ventral visual cortex, overlapping to a great extent with the scene-processing region the parahippocampal place area (PPA). Here we examined whether this ensemble region shows any sensitivity to object ensembles that contain a vertically symmetric organization. We showed observers a series of object ensembles each containing 16 individual objects organized in a four-by-four matrix. Half of the 16 objects had one identity and the other half had a different identity. For example, a display could contain 8 lemons and 8 anchors, or 8 bows and 8 bells. A total of 40 different object identities were used. Critically, in some of the displays, the objects were arranged to have a vertical symmetry, while in other displays, only horizontal or central symmetry was present. We found that PPA exhibited significantly higher responses to vertically symmetric ensemble organizations than to the other types of ensemble organizations. This effect was absent in the lateral occipital complex (LOC), a brain region previously shown to process the shapes of objects. The interaction between brain regions (LOC vs. PPA) and ensemble symmetry (presence vs. absence of vertical symmetry) was significant, with both the left and right hemispheres displaying similar activation patterns. Our results indicate that PPA may have a preference for object ensembles that have a vertically symmetric organization. Further studies will be conducted to verify this finding.
Meeting abstract presented at VSS 2013
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