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Danny Tam, Jane Shin, Andrea Li; Contributions of orientation and spatial frequency modulations in the perception of slanted surfaces. Journal of Vision 2010;10(7):69. doi: 10.1167/10.7.69.
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© ARVO (1962-2015); The Authors (2016-present)
In images of textured 3D surfaces, pattern changes can be neurally characterized as changes in orientation and spatial frequency. Previously, we have shown that correct 3D shape perception is contingent on the visibility of orientation flows running parallel to the surface curvature. However, little is known about the relative contributions of orientation and frequency information in 3D shape perception. We sought to determine the relative contributions of orientation and frequency in the perception of surface slant. Horizontal and vertical gratings were mapped onto planar surfaces that were rotated around a horizontal or vertical axis and then viewed in perspective. We measured the minimum amount of surface slant required to detect the direction of orientation (OM) or frequency modulation (OM) change (pattern detection thresholds) and compared them to the minimum amount of slant required to detect the direction of surface slant (slant detection thresholds) for the same surfaces patterned with horizontal-vertical plaids containing both OM and FM changes. For both horizontally and vertically rotated surfaces, results indicate that 1) For surfaces close to the fronto-parallel plane, steeper slants were consistently needed to detect FM (than OM) changes and to detect surface slant when both OM and FM changes were present. Slant detection thresholds were consistently close to pattern detection thresholds for OM changes. 2) For surfaces at steeper slants, preliminary results show that pattern detection thresholds are consistently low for both OM and FM conditions, and are comparable to slant detection thresholds when both types of information are present. Pattern frequencies will be varied to examine the contribution of effective contrast to FM detection. Our results suggest that 3D slant perception is dictated by OM information at both shallow and steep slants while FM information is efficiently used only at steep slants.
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