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Ignacio Serrano-Pedraza, Douglas Boegaerts, Jenny Read, David Peterzell; Orientation tuning for spatial vision and stereopsis: Factor analysis of individual differences in contrast and disparity thresholds. Journal of Vision 2018;18(10):126. doi: 10.1167/18.10.126.
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© ARVO (1962-2015); The Authors (2016-present)
Both 3D corrugations defined by binocular disparity and luminance-modulated sinusoidal stimuli are served by frequency- and orientation-tuned processes, but the number and nature of these mechanisms are not fully understood. Nor is the relationship between stereoscopic and luminance sensitive mechanisms. Here, we investigated the orientation processes that serve the detection of stereoscopic and luminance-modulated sinusoidal stimuli, using factor analyses of individual differences. In 30 participants, we used Bayesian staircases to measure (1) stereo-thresholds using sinusoidal corrugations defined by binocular disparity, and (2) contrast thresholds for detecting luminance-modulated Gabor patches. Seven orientations ranged from 0° to 90° in steps of 15°, with spatial frequency set to 0.1cpd. Thresholds for stereo showed anisotropy, increasing sigmoidally from 90° (horizontal) to 0° (vertical), while there was no oblique effect for luminance. Correlational and factor analyses for stereo thresholds revealed two broadly tuned, highly intercorrelated factors, whereas for luminance, we found three or four narrowly tuned factors almost independent of factors for other orientations. Thresholds for stereo and luminance were uncorrelated; factors for the two were independent. For stereo, finding two highly interdependent orientation processes clarifies why we (Peterzell, Serrano-Pedraza, Widdall, & Read, 2017, Vision Research) found factors tuned to high and low spatial frequencies, but which showed no selectivity for orientation (0° and 90° corrugations). The two stereo orientation factors, which seem necessary to explain anisotropy, could not be discerned in our previous study because of their broad tuning and interdependence compared to spatial frequency tuned factors, and because only two orientations were tested. For luminance, finding multiple orientation factors is consistent with previous research (Phillips & Wilson, 1984), and suggests that contrast sensitivity is determined cortically, and not by earlier circularly symmetric processes (e.g. magnocellular, parvocellular processes). The independence of factors for perceiving 3D corrugations and luminance stimuli suggests different processing streams.
Meeting abstract presented at VSS 2018
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