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Alyssa A. Brewer, Brian Barton; Pinwheel cartography: A fundamental organizing principle of the human visual system. Journal of Vision 2010;10(15):49. doi: 10.1167/10.15.49.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction: One of the more important larger scale organizing principles of visual cortical organization is the visual field map: neurons whose visual receptive fields lie next to one another in visual space are located next to one another in cortex. As increasing numbers of visual field maps have been defined in human visual cortex, one question that has arisen is whether there is an organizing principle for the distribution of these maps across visual cortex. We investigate the possibility that visual field maps are organized into similar circular clusters, which are replicated across visual cortex, oriented independently to one another, and subserve similar computations within a cluster.
Methods: We measured angular and eccentric retinotopic organization and population receptive fields across visual cortex using fMRI and population receptive field (pRF) modeling1. We model pRFs as 2-dimensional differences of Gaussians with preferred centers (x,y) and spreads (sigma), convolve the predicted response to the stimuli with the haemodynamic response function, and fit the best pRF independently to each voxel via a least-squares method. Retinotopic stimuli consisted of black and white, drifting bar apertures comprised of flickering checkerboards (11° radius).
Results/Discussion: We identify 14 new visual field maps in occipital cortex, organized with previously defined visual field maps into 6 visual field map clusters: Occipital Pole (OP), V3A/B, Temporal-Occipital (TO), Inferior Temporal-Occipital (ITO), Ventral-Occipital (VO), and posterior Superior Temporal Sulcus (pSTS). We propose that these pinwheel clusters are a fundamental organizing principle of the human visual system, extending from low-level to higher-order visual processing areas.
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