Examining how the real-world size of objects is represented in ventral visual cortex

Konkle & Oliva

The size of objects in the world influences how we interact with them, but little is known about how known physical size is involved in object processing and representation. Here we examined if the dimension of real-world size is systematically represented in ventral visual cortex. In Experiment 1, observers were presented with blocks of small objects (e.g. strawberry, calculator) and blocks of big objects (e.g. car, piano) displayed at the same visual size (8 degrees) while undergoing whole brain imaging in a 3T fMRI scanner. Contrasts of big and small objects revealed that a region in the parahippocampal gyrus was preferentially active to big objects versus small objects, while a subregion along the lateral occipital cortex was preferentially active to small objects versus big objects. In Experiment 2, objects with big and small real-world sizes were displayed at two visual sizes on the screen (10 degrees and 4 degrees). The same regions were selective for big or small objects, independent of the visual size presented on the screen, indicating that these regions are tolerant to changes in visual size. In Experiment 3, observers were shown blocks of objects grouped by category, with 16 different object categories spanning the range of real-world sizes. We observed parametric modulation of the big and small regions of interest–in the big ROI, activity increased as object size increased (r=.74, p<.01), whereas in the small ROI the opposite pattern was observed (r=-.76, p<.01), with no modulation in LOC (r=-.28, p>.1) or early visual cortex (r=.05, p>.1). These results suggest that activity in the ventral visual cortex depends systematically on real-world size. Whether this modulation is based on accessing existing knowledge, or by a combination of low-level properties that are correlated with real-world size, these results highlight a new dimension of information processing in ventral visual cortex.

Konkle, T. & Oliva, A. (2010). Examining how the real-world size of objects is represented in ventral visual cortex. Journal of Vision. 10(7): 982; doi:10.1167/10.7.982