Reverse engineering brain networks for scene and object processing with non-invasive neuromodulation

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OBJECTIVE: Mounting evidence from behavioural measures, neuroimaging and clinical data has shown that objects and scenes are processed independently and that, counterintuitively, a scene can be categorized without the need to recognize any of its constituent objects. The goal of this research program is to examine the relationship between object and scene processing and, in particular, the contribution of object-selective cortical areas to scene processing and their corollary. My laboratory has demonstrated that non-invasive neuromodulation of object-selective cortex with transcranial magnetic stimulation (TMS) has remote effects across the brain in scene processing regions and behaviourally, it alters our ability to perceive scenes. This observation suggests for the first time that object and scene processing may not be as independent as previously thought but might instead involve mutual connections. In the proposed research program I will assess the functional connectivity of object-preferential cortex on scene perception and scene-preferential cortex on object perception at both the behavioural and neural level. ******SCIENTIFIC APPROACH: I will use several complementary methods, including functional magnetic resonance imaging (fMRI), functionally-guided TMS, and behavioural measures. I propose three main experiments to address the following questions: ******1. What level of semantic coding is performed in object-preferential and scene-preferential cortices? When does it occur? I will perform offline TMS to object-preferential and scene-preferential cortices to determine the contribution of these regions to levels of semantic coding of objects and scenes. Subsequently, online TMS will be performed to determine the temporal coding in the neuromodulated target object and scene regions. ***2. What is the functional connectivity between object and scene processing cortical areas? I will use a consecutive TMS-fMRI design to measure scene- and object-induced BOLD signal in the object and scene-preferential cortical networks following offline low frequency repetitive TMS to object and scene-preferential cortex. In a similar paradigm, I will apply TMS online during fMRI scanning using an MR-compatible coil to observe real-time neuromodulatory effects in remote regions to the stimulation site. ***3. What is the anatomical connectivity between the lateral occipital (LO) object-selective area and scene-selective cortex? I will use diffusion tensor imaging (DTI) to determine white matter connectivity between these areas.******NOVELTY AND SIGNIFICANCE: This novelty and significance of this research is that it will further refine our understanding of how visual image processing networks in the cortex interact.