Almost all fMRI studies of object recognition have focused on the geometric structure of objects. Little attention has been paid to the recognition of material properties from surface-based visual cues. Even when the processing of surface-based cues, such as colour and texture, has been studied, it has been in the context of using these cues to reveal the geometric structure of objects. Thus, the goal of the current experiment was to uncover the functional geography of occipito-temporal brain areas mediating the processing of ‘stuff’ (material properties) versus ‘things’ (geometric form). Using fMRI, we scanned participants as they attended to either the 3-D structure or the material properties of the same unfamiliar ‘nonsense’ objects. Attention was manipulated by asking participants to perform a discrimination task in which they had to decide whether pairs of objects had the same or different 3-D geometry, or whether the objects shared the same or different material properties (wood, granite, steel, plastic, etc.). We also included trials in which participants had to decide whether the pairs of objects had the same or different orientation. Results indicated that there was significantly more activation in the lateral-occipital area (area LO) when attention was directed to the 3-D structure (compared to both orientation and material properties) of objects. In contrast, areas in the fusiform gyrus (including the fusiform face area and area V8) and parahippocampal cortex (including the parahippocampal place area) responded preferentially when participants attended to the material properties of objects. [Interestingly, an area in the caudal intraparietal sulcus (area cIPS) was more sensitive to the orientation of objects, compared to 3-D geometry and material properties.] We conclude that object recognition is subserved in part by functionally separable occipito-temporal brain regions mediating the processing of ‘stuff’ versus ‘things’.

Supported by a grant from Canadian Institutes of Health Research to M.A.G.