The objects behind the scenes: TMS to area LO disrupts object but not scene categorization

Abstract

Many influential theories of scene perception are object centered (Biederman, 1981) suggesting that scenes are processed by extension of object processing in a bottom-up fashion. However, an alternative approach to scene processing is that the global gist of a scene can be processed in a top-down manner without the need for first identifying its component objects (Oliva & Torralba, 2001). This suggests that global aspects of a scene may be processed prior to the identification of individual objects. Evidence from a patient with object agnosia and bilateral damage to lateral occipital (LO) cortex, an area associated with object processing (Grill-Spector et al., 2001), also suggests that scene categorization can operate independently of object perception (Steeves et al., 2004). We asked whether or not temporary interruption to area LO in neurologically-intact controls with repetitive transcranial magnetic stimulation (rTMS) impairs object and scene processing. Participants categorized greyscale images of objects and scenes as ‘natural’ or ‘man-made’. Subsequently, we targeted area LO, which had been functionally defined with fMRI, and participants underwent five minutes of rTMS. Immediately following, they completed another version of the object and scene categorization task. Preliminary results show that rTMS to area LO impairs categorization of objects but not scenes. This suggests that the global gist used to rapidly categorize scenes remains intact despite an interruption to object processing brain regions.