Investigating scene processing in the human brain

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Retinotopy - the spatial mapping of the retina across the cortical surface - and category-selectivity - the maximal response of brain regions to particular stimulus categories - are two fundamental organising principles of human visual cortex. Until relatively recently these principles were considered largely independently but are now known to be co-localised in the brain.

One such area, the Occipital Place Area (OPA) not only exhibits scene-selectivity, but also, spatially overlaps at least five separate visual field maps. The role that each visual field map plays in the pattern of responses evidenced at the level of the OPA remains unknown but raises the possibility that they each contribute a set of unique, yet complementary computations. Such a proposition was confirmed recently by our team, with respect to two visual field maps (LO1 and LO2) and the processing of orientation and shape, respectively.

The demonstration that individual visual field maps contribute unique computations provides a novel framework for understanding complex visual processing, namely, that different visual features are computed in parallel by discrete regions that map the visual field. It is this framework that we aim to exploit in order to probe the functional properties of the visual field map divisions of OPA. We will capitalise on the spatial resolution of fMRI, the temporal resolution of MEG and the causal nature of TMS to provide a comprehensive account of the roles played by OPA visual field maps in complex visual processing. First, fMRI will be used to define both OPA and its visual field map divisions using cutting-edge visual field mapping techniques. Second, we will measure and evaluate what visual features these regions respond to and when such processing occurs, through a combination of fMRI, MEG, eye-tracking and behavioural experiments. Finally, we will test the causal role these visual field maps play in scene perception through retinotopically-guided TMS.