Simulation of artificial vision: I. Eccentric reading of isolated words, and perceptual learning

Article Article scientifique Article Simulation of artificial vision: I. Eccentric reading of isolated words, and perceptual learning eng 2003 author Sommerhalder Jorg 23916 author Oueghlani Evelyne Farida 87674 author Bagnoud Marc André 83878 author Leonards Ute 523836 author Safran Avinoam B. 25462 author Pelizzone Marco 26345 269-283 10.1016/s0042-6989(02)00481-9 12535986 0042-6989 Simulations of artificial vision were performed to assess "minimum requirements for useful artificial vision". Retinal prostheses will be implanted at a fixed (and probably eccentric) location of the retina. To mimic this condition on normal observers, we projected stimuli of various sizes and content on a defined stabilised area of the visual field. In experiment 1, we asked subjects to read isolated 4-letter words presented at various degrees of pixelisation and at various eccentricities. Reading performance dropped abruptly when the number of pixels was reduced below a certain threshold. For central reading, a viewing area containing about 300 pixels was necessary for close to perfect reading (>90% correctly read words). At eccentricities beyond 10 degrees, close to perfect reading was never achieved even if more than 300 pixels were used. A control experiment using isolated letter recognition in the same conditions suggested that lower reading performance at high eccentricity was in part due to the "crowding effect". In experiment 2, we investigated whether the task of eccentric reading under such specific conditions could be improved by training. Two subjects, naive to this task, were trained to read pixelised 4-letter words presented at 15 degrees eccentricity. Reading performance of both subjects increased impressively throughout the experiment. Low initial reading scores (range 6%-23% correct) improved impressively (range 64%-85% correct) after about one month of training (about 1 h/day). Control tests demonstrated that the learning process consisted essentially in an adaptation to use an eccentric area of the retina for reading. These results indicate that functional retinal implants consisting of more than 300 stimulation contacts will be needed. They might successfully restore some reading abilities in blind patients, even if they have to be placed outside the foveal area. Reaching optimal performance may, however, require a significant adaptation process. Adult Blindness/rehabilitation Humans Learning/physiology Middle Aged Pattern Recognition, Visual Photic Stimulation/methods Prostheses and Implants Prosthesis Design Reading Recognition (Psychology)/physiology Retina/physiology Vision, Binocular/physiology Vision, Monocular/physiology Visual Fields/physiology Dewey 616.8 53 Département de neurosciences fondamentales 21A 61 Département des neurosciences cliniques 226 false 582 Ophtalmologie expérimentale 925 Vision research 43 3 a76326d3-a297-4964-a6d3-66c440e0393e Article (Published version) Public 1-s2.0-S0042698902004819-main.pdf 740304 application/pdf openAccess Faculté de médecine / Section de médecine fondamentale / Département de neurosciences fondamentales Faculté de médecine / Section de médecine clinique / Département des neurosciences cliniques

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Simulation of artificial vision: I. Eccentric reading of isolated words, and perceptual learning	Vision research			2003	479	341

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Oueghlani, Evelyne Farida