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Aaron Johnson, Bruno Richard, Dave Ellemberg, Bruce Hansen; Eccentricity-dependent sensitivity loss of amplitude spectrum slope discrimination.. Journal of Vision 2013;13(9):1237. doi: https://doi.org/10.1167/13.9.1237.
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© ARVO (1962-2015); The Authors (2016-present)
Natural scenes exhibit much statistical regularity. Perhaps the most explored regularity is the association between spatial frequency (f) and the amplitude of each spatial frequency component (i.e., their second-order statistics). This association is present in virtually all natural scenes and follows the general form: amplitude = 1/f[sup]α[/sup], with the slope (α) commonly being between 0.6 and 1.6. Although researchers have shown that humans are sensitive to changes in the slope, these studies have measured sensitivity at (or near) the fovea only. Sensitivity to visual acuity and contrast decreases as eccentricity from the fovea is increased, and this eccentricity-dependent loss in sensitivity may affect the ability to detect changes in the amplitude spectrum slope. Participants were presented a series of broadband noise stimuli with different amplitude spectrum slopes (α = 0.4, 0.6, 0.8, 1, 1.2, & 1.4) at various eccentricities (0, 0.5, 1, 2, 4, & 8 degrees) by means of a gaze-contingent multi-resolution display (GCMRD) 2-IFC. The GCMRD presents the un-altered amplitude slope value at fixation, and in one of the intervals, presents a peripheral image for which the slope is changed. Thresholds were calculated with a Psi adaptive threshold method. For foveal and parafoveal conditions (<1 degree), our results replicated previous findings. Thresholds where the lowest when the slope of the amplitude spectrum was 1.2 and 1.4, while they were highest for slopes of 0.6 and 0.8. However, all thresholds increased for eccentricities greater than 1 degree. The rise in threshold was the greatest for amplitudes that ranged from 0.4 to 1, and the least for amplitude slope values greater than 1. We interpret these data such that the eccentricity dependent sensitive loss in amplitude spectrum slope discrimination is due to the lower and more limited range of spatial frequencies available to encode the amplitude spectrum at greater eccentricities.
Meeting abstract presented at VSS 2013
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