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Caitlin Mullin, Jennifer Steeves; rTMS to object selective cortex: Evidence of an inverse relationship between object and scene processing using fMRI. Journal of Vision 2012;12(9):124. doi: 10.1167/12.9.124.
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BACKGROUND: 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). Transient inactivation of the object selective lateral occipital area (LO) of the brain using repetitive transcranial magnetic stimulation (rTMS) has been shown to interrupt object processing yet facilitate scene processing, suggesting a release of inhibitory connections between object and scene pathways (Mullin & Steeves, 2011). The current project further investigates the nature of this interaction between object and scene selective cortex using interleaved rTMS and functional magnetic resonance imaging (fMRI). METHODS: Subjects participated in two sessions of 1 Hz rTMS to area LO and to the vertex (control site). Following each session, subjects performed a one-back repetition task while viewing scene and object stimuli during fMRI. A region of interest analysis was performed on the independently defined object selective LO and the scene selective parahippocampal gyrus (PPA). Peak BOLD activation and beta weights were compared in the two rTMS conditions as well as a third No-rTMS condition. RESULTS: Subjects showed a significant reduction in peak BOLD activation and beta weights in LO subsequent to rTMS to LO compared to the vertex and No-rTMS conditions. In addition, scene selective PPA activation tended to increase subsequent to rTMS to LO compared to the vertex and No-rTMS conditions. CONCLUSION: The transient deficit in object categorization introduced by rTMS to LO that we have previously described is associated with a significant reduction in BOLD signal and beta weights in area LO but an increase in activation in the PPA.
Meeting abstract presented at VSS 2012
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