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M. C. Morrone, G. D'Avossa, M. Tosetti, D. C. Burr; Modulation of retinotopy of human MT complex by gaze position. Journal of Vision 2006;6(6):82. doi: https://doi.org/10.1167/6.6.82.
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Gaze direction affects visually evoked activity in extra-striate and parietal areas of the macaque, and the strength of several visual aftereffects in humans. Here we examine the effect of gaze on BOLD responses in human MT complex (hMT). During fMRI scanning, subjects were required to discriminate the direction of motion of a brief weak motion signal embedded within a square random noise display of 7 X 7 degrees. Subjects gazed in one of three directions (centre or 10° left or right, monitoring eye position) with stimuli displayed 10° left or right of fixation. In separate sessions conducted during passive viewing, the retinotopic portion of area hMT was localized on the basis of a clear contra-lateral response and on the selectivity to coherent optic flow motion. In retinotopic regions of the occipital lobe (V1 and V2) there was no evidence of a gaze direction effect on the visually evoked BOLD response. However, in the visuo-topic portion of hMT the response was strongly modulated by gaze: indeed the response depended more strongly on spatial position on the screen than on retinal position (that varied with gaze), suggesting spatio-topic mapping. In a further condition subjects were required to make a saccade between presentations of the motion sequence: again the BOLD response showed integration of the retinotopically disparate stimuli. We suggest that gaze related modulation may support transformation of visual information from a retinal to a spatial reference frame early in the analysis of visual motion.
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