Body-extending object effectors: organization of ventral stream object representations reflects body-object interactions
21.24, Saturday, May 11, 8:15 - 9:45 am, Royal Ballroom 4-5
Stefania Bracci1, Marius Peelen1; 1Center for Mind/Brain Sciences, CIMeC - Trento University
The functional organization of high-order visual cortex is not fully understood. Using fMRI, we provide evidence for a new organizational principle by showing that activity in part of ventral visual cortex reflects the degree to which objects are perceived to physically and functionally extend the body. In 4 studies, we measured the distribution of ventral stream responses evoked by pictures of a wide range of objects. These objects were independently rated on several action-related dimensions used to model evoked neural activity. Additionally, the ratings were used to create a similarity space capturing the similarity of the objects on the action-related dimensions, which allowed us to test for brain regions in which multivoxel activity patterns reflected these similarity spaces. Results revealed a selective overlap between representations of body effectors (e.g., hands, feet, and limbs) and representations of body-extending object effectors (e.g., hammers, combs, and tennis rackets). Multiple regression analysis revealed that the response profile of a region in left lateral occipitotemporal cortex (LOTC) reflected the degree to which objects were rated as extensions of the body. This effect was significantly more pronounced in hand-selective voxels than in body-selective voxels and was not observed for other action-related object dimensions, such as hand priming, hand grasping, and hand-action centrality. Finally, whole-brain representational similarity analysis showed that the similarity of multivoxel object response patterns in left LOTC predicted the perceived similarity in the degree to which objects extend the body. No such relation was found for ratings of other action-related object dimensions. Together, these results reveal a clustering of body and object effector representations, indicating that the organization of object representations in the ventral visual pathway partly reflects how the body interacts with objects. More generally, they provide evidence that action-related object properties influence the functional organization of object representations in the ventral stream.