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F Pei, Y Bonneh, V Sampath, C Hou, AM Norcia; Development Of Visual Integration Of Local Features Into Uniform Textures . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3994.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:Textures are patterns that have regularities in spatial scale and orientation. Texture discrimination requires the registration of the statistical distribution of local orientation and scale measurements. Here we asked whether young infants can discriminate textures that differ only in their orientation statistics. Methods:We recorded Visual Evoked Potentials (VEP) to textures based on Gabor patches. In the first experiment, we measured responses to an organized texture (all patches vertical) that was alternated at 1Hz with a random texture (each element was oriented randomly). We compared this test condition with a control condition consisting of the alternation between two independently random configurations in 10 adults and 30 infants between 8.4 to 35.4 weeks of age. In the second experiment, the global orientation of the organized pattern changed randomly, rather than always being vertical (10 adults and 11 infants between 25.4 to 30.7 weeks of age). The carrier of each Gabor was 2.45cpd and the envelope allowed 2 full cycles to be visible. The center to center separation between each Gabor was 3 lamda. VEP amplitude and phase were measured for the first to the ninth harmonics. Results:In each experiment both infants and adults showed significant first harmonics in the test condition that was not present in the control condition. The presence of odd-harmonic components indicates that the response to the transition from organized to random textures was not the same as that from random to organized. Conclusion:Discrimination of organized and random textures in experiment 2 could only have been accomplished by comparing relative orientation of two or more patches. There was no local information at a single patch that distinguished the two textures. Therefore, we conclude that texture discrimination can be accomplished on the basis of orientation information alone no later than 6 months of age. The stimulus of experiment 1 did have a local cue --- every other update of the image contained a vertical patch. Local mechanisms, such as orientation-specific adaptation could possibly have contributed to this response. Further experiments with the stimulus of the second experiment are needed to establish the age of onset of texture discrimination in the VEP.
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