Organizing visual object knowledge by real-world size in ventral visual cortex

Konkle & Oliva

Across ventral visual cortex, there are multi-voxel patterns that are reliable and informative about different object categories. However, little is known about whether there is a systematic organization underlying these patterns of activity for different visual objects. While there are many possible overarching organizing dimensions for objects, one fundamental dimension of all real-world objects is their physical size. This dimension is intrinsically involved in how we interact with and experience different objects. Here, we examined the possibility that visual object knowledge in the ventral visual cortex is organized by real-world size.

While undergoing whole brain imaging in a 3T fMRI scanner, observers (N=8) were presented with a stream of objects one at a time for 1 second each. The objects systematically swept through the range of real-world size from small to large (or large to small) every 24 seconds. We used phase-encoding analyses traditionally employed for retinotopic mapping to compute the preferred phase of each voxel and construct lag maps across ventral visual cortex. All but one observer showed a systematic size-related organization of activation, with larger objects activating more medial aspects of the ventral visual cortex and smaller objects activating more lateral aspects of the ventral visual cortex. A smooth continuum across the range of object size was seen in half the observers, while a more categorical (big-medial/small-lateral) organization was seen in the remaining participants.

These data suggest that spatially distributed multi-voxel patterns of activity in ventral visual cortex for different object categories may reflect a systematic high-level organization. The real-world size of the object is thus a potential organizing dimension for visual object knowledge and may be used as a proxy for where in ventral visual cortex different objects are processed and represented.

Konkle, T., & Oliva, A. (2011). Organizing visual object knowledge by real-world size in ventral visual cortex. Poster to be presented at the annual meeting of the Vision Sciences Society, May 6-12, Naples, FL.