Poster E126, Monday, March 27, 2:30 – 4:30 pm, Pacific Concourse
Representation of object affordances in the posterior parietal lobe
Chenxiao Guan1, Quanjing Chen1, Colleen L. Schneider1, Bradford Z. Mahon1; 1University of Rochester, USA
When we see an object and plan to grasp it, both the ventral and dorsal visual processing pathways are engaged and involved in generating the appropriate action to the object. While the ventral visual stream is associated with high-level visual processing and object recognition, the dorsal visual stream supports the extraction of volumetric properties of objects necessary to plan appropriate actions. Here, we used multivoxel pattern analyses over functional MRI data to test whether the left posterior parietal cortex and the fusiform gyrus represent object affordances. Participants viewed elongated manipulable objects rotating around their center of mass in depth. We hypothesized that if a region carries information about object affordances, it should be able to discriminate the direction which a tool is pointing, and specifically should distinguish a given orientation of a tool from the 180 degree rotation of the same tool (i.e., the handle of an object from its ‘business end’). Region of interest (ROI) analyses showed that the posterior parietal lobe could distinguish tool orientation when offset by 180 degrees, but not when offset by 45 degrees. In contrast, responses in the fusiform gyrus could distinguish between orientations that differed by 45 degrees, but not by 180 degrees. These findings suggest that the posterior parietal lobe may play a critical role in the representation of object affordances.
Topic Area: PERCEPTION & ACTION: Vision