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Erez Freud, Jody Culham, David Plaut, Marlene Behrmann; The large-scale organization of object processing in the ventral and dorsal pathways. Journal of Vision 2017;17(10):286. doi: https://doi.org/10.1167/17.10.286.
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© ARVO (1962-2015); The Authors (2016-present)
One of the hallmark properties of the ventral visual pathway is sensitivity to object shape. Accumulating evidence, however, suggests that object-based representations are also derived by the dorsal visual pathway although less is known about the characteristics of these representations, their spatial distribution, and their perceptual importance. To bridge this gap, the present study combined psychophysical and fMRI experiments in which participants viewed and recognized objects with different levels of scrambling that distorted object shape. Neural shape sensitivity was assessed by measuring the reduction of fMRI activation in response to scrambled versus intact versions of the same stimulus. In the ventral pathway, shape sensitivity increased linearly along an anterior-posterior axis from early visual cortices (i.e., v1-v4) to posterior extrastriate cortices (i.e., LO1) and remained constant along the occipitotemporal cortex. In the dorsal pathway, shape sensitivity also increased linearly along an anterior-posterior axis from early visual cortices (i.e., v1-v3d) to posterior extrastriate cortices (i.e., V3a, posterior IPS). However, in stark contrast to the ventral stream, in moving from posterior extrastriate cortices to more anterior regions (i.e., IPS 1-4, aIPS), shape selectivity gradually decreased. Interestingly, as with the anterior ventral pathway, the posterior IPS activation profile was found to be highly correlated with recognition performance obtained outside of the scanner, further pointing to a plausible contribution of this region to perception. Finally, these results were replicated using a different method for manipulating object integrity (diffeomorphic alteration) suggesting the results are not attributable to modulations of low-level object features. Together, these results provide novel evidence that object representations along the dorsal pathway are not monolithic and gradually change along the posterior-anterior axis. These findings challenge the binary dichotomy between the two pathways and suggest that object recognition might be the product of more distributed neural mechanisms.
Meeting abstract presented at VSS 2017
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