fMRI and behavioural investigations of the processing of shape and surface properties in object perception.

摘要

Humans have the ability to recognize objects in their environment from a number of different visual features, such as their shape and their material properties (from surface-based visual cues such as colour and texture). Most studies of object recognition, however, have focused on shape, and thus comparatively little is known about how the brain processes surface and material properties to accomplish successful object recognition. To investigate this, I used functional magnetic resonance imaging (fMRI) and behavioural paradigms to study the interactions between shape, colour, and texture in the human brain.;But demonstrating that separate brain regions process shape and surface properties does not necessarily mean that these brain regions function independently. Thus, in a second project, I used a behavioural attentional paradigm to show that the separate brain regions recruited during the perception of shape and surface properties can indeed function independently during object recognition---at least under conditions where perceiving the surface properties means perceiving the material from which the objects were made (Chapter 3; Cant et al., 2008).;But it is also possible for surface properties to provide cues to an object's shape (e.g. shape-from-texture and shape-from-shading), and when this is the case, the processing of these attributes may be more interactive. Thus, in a third project, I used stimuli where surface properties contribute more directly to the perception of 3-D shape, and using the same attentional paradigm used in the second project, I demonstrated that shape and surface properties in this situation are not processed independently, and instead appear to share common processing resources (Chapter 4; Cant & Goodale, 2009).;Taken together, these neuroimaging and behavioural studies suggest that there are different networks of processing for visual surface properties - one network where surface cues contribute to the perception of object shape, and another network where surface cues contribute to the perception of an object's material properties. These findings elaborate on current models of object recognition by providing a detailed account of the types of cues we use to recognize objects (i.e. stressing the importance of both shape and surface properties). In addition, these findings suggest that current models of visual cortical organization should focus not only on the particular stimulus category to which a region maximally responds (e.g. objects, faces, scenes), but also on the stimulus attributes that best support the processing of that category (e.g. shape, surface properties). Importantly, this principle may also apply to the organization of other cortical sensory systems.;In a first project, I used fMRI and provided evidence for the existence of a functional and anatomical sub-division for processing the shape and the surface properties of objects in the visual system (Chapter 2; Cant, Amott, & Goodale, 2009). Specifically, shape is processed in more lateral regions of the visual system (such as the lateral occipital area, or area LO), whereas surface properties are processed in more medial and anterior regions (such as the collateral sulcus).;Keywords. vision, object recognition, perception, shape, surface properties, colour, texture, material properties, attention, fMRI, occipito-temporal cortex