Abstract
The current dominant view on object processing entails that abstract object shape is represented in the ventral visual stream (occipito-temporal cortex). This bias towards the ventral stream has diverted the attention of the field from rigorous study of object responses in the dorsal stream (parietal cortex). To fill the gap in our understanding of object responses in the dorsal stream, we ran a series of experiments using functional MRI to comprehensively study object responses in the human dorsal stream and compared them to those in the ventral stream. We found robust object responses in both streams. Responses in the dorsal parietal cortex, similar to those in the ventral occipitotemporal cortex, were tolerant to changes in position, size, low-level features, and attentional tasks and were sensitive to both static and dynamic cues in the stimuli. In a data-driven approach, we compared the representational structures across the brain. The structure of the visual system, including the visual hierarchy and the dorsal-ventral distinction, emerged from this analysis. Dorsal Stream Regions differed from those in the ventral pathway and early visual cortices. In fact, the structure of the visual hierarchy and the dorsal-ventral stream distinction could be recovered through this bottom-up analysis. The rediscovery of the two-pathway structure using an entirely bottom-up approach demonstrates that first, two pathways exist in the brain for processing object shape information, and second, the dorsal pathway represents features in the visual input distinct from those represented in the ventral pathway.