Tripartite Organization of the Ventral Stream by Animacy and Object Size

Konkle & Caramazza

Occipito-temporal cortex is known to house visual object representations, but the organization of the neural activation patterns along this cortex is still being discovered. Here we found systematic, large-scale structure in the neural responses related to the interaction between two major cognitive dimensions of object representation--animacy and real-world size. Neural responses were measured with functional magnetic resonance imaging while human observers viewed images of big and small animals, and big and small objects. We found that real-world size drives differential responses only in the object domain, not the animate domain, yielding a tripartite distinction in the space of object representation. Specifically, cortical zones with distinct response preferences for big objects, all animals, and small objects, are arranged in a spoked organization around the occipital pole, along a single ventral-medial, to lateral, to dorsal-medial axis. The preference zones are duplicated on the ventral and lateral surface of the brain. Such a duplication indicates that a yet unknown higher order division of labor separates object processing into two sub-streams of the ventral visual pathway. Broadly, we suggest that these large-scale neural divisions reflect the major joints in the representational structure of objects, and thus place informative constraints on the nature of the underlying cognitive architecture.

Konkle, T., & Caramazza, A. (in press). Tripartite Organization of the Ventral Stream by Animacy and Object Size. Journal of Neuroscience .