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Jonathan S. Cant, Yaoda Xu; Object ensemble coding is distinct from texture processing in the parahippocampal place area. Journal of Vision 2011;11(11):877. doi: 10.1167/11.11.877.
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© ARVO (1962-2015); The Authors (2016-present)
Using the fMRI-adaptation paradigm, we have previously demonstrated that the parahippocampal place area (PPA) is insensitive to image changes as long as the same ensemble of objects is perceived across two images (e.g. two different images of the same strawberry pile). We also showed that this object ensemble processing is remarkably similar to the processing of visual texture in the PPA. This raises the question of whether or not the processing of ensembles in the PPA simply reflects the processing of the texture of the individual objects in the ensemble, rather than ensemble features per se. To address this question, we again used the fMRI-adaptation paradigm and in separate trials we showed participants a sequence of two ensemble images that were either identical, shared object ensemble features (i.e. two different images of the same ensemble), or different (i.e. the shape of the individual ensemble objects differed). Importantly, the texture/material of the individual objects in the ensembles was identical in all conditions. Using an independent localizer approach, our results indicate that the PPA shows a lower response in both the ‘identical’ and ‘shared’ conditions (which did not differ), and a higher response in the ‘different’ condition. Thus, the PPA shows adaptation when the same ensemble is repeated and a release from adaptation when two different ensembles are presented despite the repetition of the texture/material of the individual objects in the two ensembles. This indicates that the response to object ensembles in the PPA is not driven solely by the perception of the texture of the individual objects in an ensemble, but instead reflects the perception of the entire object ensemble.
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