Final Report Summary - PRF MODELS (Computational neuroimaging: quantitative models of human visual neurons) We have extended computational neuroimaging techniques from basic science to applied neuroscience. We applied neuropsychological, functional magnetic resonance and diffusion tensor imaging techniques. In particular, our aim was to develop biologically-inspired model-based data-analysis techniques, i.e. the pRF method (Dumoulin & Wandell, 2008). Neuropsychological evaluation of two stroke patients revealed that specific deficits in motion perception. These results provide evidence for several distinct mechanisms to process motion in the human visual system, specifically provide evidence for the existence of at least three motion mechanisms in the human visual system: a low-level first- and second-order motion mechanism and a high-level attention or position-based mechanism. Furthermore, we have provided evidence for both stability and plasticity in an extremely rare congenital disorder, human achiasma. We studied two of these subjects, which required collaboration between nine different universities worldwide, state-of-the-art techniques, and specific adjustments in the pRF method. We found that highly atypical functional responses in the cortex, including overlapping hemifield representations and bilateral population receptive fields in both striate and extrastriate visual cortex. Yet, the effect on visual perception and daily life is not easily detected, and the gross geniculostriate and occipital callosal connections remains largely unaltered. We suggest conservative geniculostriate and cortico-cortical mapping of abnormal retinogeniculate input provides a sufficient scope of developmental plasticity in humans to make substantially abnormal representations available for relatively normal visual perception.
