Abstract
Although there is mounting evidence that input from the dorsal visual pathway contributes to object recognition processes in the ventral pathway, the dorsal pathway is rarely included in conceptual or computational models of visual recognition. One reason for this exclusion is that the specific functional contributions of dorsal cortex to object recognition are poorly understood. Given its classic role in computing spatial relations, we hypothesized that the dorsal pathway may compute the object-centered relations among an object’s component parts (i.e., its topological structure) and propagate this information to the ventral pathway to support object categorization. Using multiple functional localizers, we found regions in the posterior and anterior intraparietal sulcus (IPS) with selectivity for part relations. These regions were found most strongly in the right hemisphere, and their selectivity was independent of allocentric relations and other dorsal object representations, such as 3D shape and tools. Importantly, these regions exhibited task-dependent functional connectivity with ventral cortex, such that connectivity increased in conditions where part relations differed. Next, we examined whether and how these regions might support object categorization. We found object category could be decoded in right pIPS at levels comparable to ventral object regions (e.g., LOC). Moreover, similarity analyses suggested that decoding in right pIPS was supported by a representation of object-centered relations, as approximated by a skeletal model, and not by low- or high-level image properties as approximated by Gabor or neural network models. Interestingly, we found that the multivariate response in right pIPS mediated representations of part relations in ventral cortex, a finding further supported by its multivariate connectivity to ventral cortex. Altogether these findings highlight how object-centered part relations, a property crucial for object recognition, are represented neurally. Moreover, these findings provide further evidence of a strong link between dorsal and ventral visual pathways in accomplishing object recognition.