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In Search of Texture Integration in the Early Visual Cortex

Foekema, S. (2010) In Search of Texture Integration in the Early Visual Cortex. Master's Thesis / Essay, Artificial Intelligence.

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In normal vision, objects, faces, and letters are centered onto the retina. One reason for this is that compared to foveal vision, peripheral vision lags the acuity to extract details. Another reason is a phenomenon called crowding. The crowding effect entails excessive grouping of visual features and is bound to a critical region that is linearly proportional to the viewing eccentricity. After decades of research, inappropriate ‘hardwired’ integration of afferent visual information in the visual cortex is the prevailing explanation of crowding. The aim of this research is finding the neural correlates of ‘integration fields’ in the early visual cortex using functional Magnetic Resonance Imaging (fMRI). The study comprised two fMRI experiments. Firstly, a standard visual field mapping procedure was performed that allowed the delineation of visual cortical regions. Secondly, fMRI responses were measured to the presentation of orientation-based texture stimuli where second-order orientational differences induce the percept of an illusory contour. This enabled a signature plot of neuronal integration processes in the early visual cortex as a function of cortical distance to the illusory contour. The resulting signature revealed integration processes as early as V1 and are compared with a biologically plausible model of crowding.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Artificial Intelligence
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 07:31
Last Modified: 15 Feb 2018 07:31

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