Periodicity in orientation discrimination and the unconfounding of visual information |
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| Authors: | D Regan P Price |
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| Affiliation: | 1. Department of Pediatrics, Cardinal Tien Hospital and School of Medicine, Colloge of Medicine, Fu-Jen Catholic University, New Taipei City, Taiwan;2. Department of Intensive Care Medicine, Chi Mei Medical Center, Liouying, Tainan, Taiwan;3. Department of Internal Medicine, Cardinal Tien Hospital and School of Medicine, Colloge of Medicine, Fu-Jen Catholic University, New Taipei City, Taiwan;4. Medical Research Center, Cardinal Tien Hospital and School of Medicine, Colloge of Medicine, Fu-Jen Catholic University, New Taipei City, Taiwan;5. Department of Dentistry, Cardinal Tien Hospital and School of Medicine, Colloge of Medicine, Fu-Jen Catholic University, New Taipei City, Taiwan;6. Department of Pediatrics, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan;7. Institute of Population Health Sciences, National Health Research Institutes, Zhunan, Miaoli County, Taiwan |
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| Abstract: | Orientation discrimination is a periodic function of mean orientation. Discrimination sensitivity (i.e. threshold-1) was measured at 7.5 deg increments around the clock for an 8 c/deg grating subtending 1.0 deg dia located 1.25 deg from the foveal centre. Discrimination sensitivity was best for horizontal and vertical orientations, but did not fall monotonically to minima at 45 deg and 135 deg. Instead it fell precipitously to minima at angles of only 20 deg to the horizontal and vertical, and there was a weak submaximum near 45 deg. This finding is consistent with the proposal that orientation discrimination is determined by the relative activity of broadly-tuned, orientation-sensitive neural elements, and that only a small number of elements are effective in any small retinal region. This idea can also explain why subjects do not confound a change of orientation with a simultaneous change of contrast or spatial frequency. |
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