Spatial scaling of vernier acuity tasks

doi:10.1016/0042-6989(92)90204-V

Vision Research

Volume 32, Issue 8, August 1992, Pages 1481-1491

https://doi.org/10.1016/0042-6989(92)90204-V Get rights and content

Abstract

Vernier acuity thresholds for two abutting lines and for a two-dot stimulus were measured as a function of stimulus magnification at eccentricities of 0, 5, 10 and 15 deg using a spatial scaling technique in which all stimuli are simply magnified versions of each other. The advantage of such a technique is that no prior knowledge of a suitable magnification factor with which to increase the size of peripheral stimuli is required. Thresholds for the line stimulus could be successfully scaled by the application of a magnification factor with an E₂ value of 1.23–1.78 deg. Further, provided that the effects of dot separation and eccentricity were dissociated, spatial scaling with an E₂ value of 1.06–1.96 deg was also successful in removing eccentricity dependence for two-dot vernier thresholds.

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It has been known that scotopic Vernier acuity is 10 times lower than photopic Vernier acuity (Freundlieb, Herbik, Kramer, Bach, & Hoffmann, 2020; Livingstone & Hubel, 1994). However, detection threshold of shape frequency obtained around the highest sensitivity range is comparable to Vernier acuity under photopic viewing conditions (Westheimer, 1982; Whitaker et al., 1992). It has also been shown that Vernier acuity within the 10 deg eccentricity from the fovea is processed by a similar mechanism that for foveal Vernier acuity (Levi & Waugh, 1994).
Tyler (Journal of Physiology 228 (1973) 637–647) reported that the sensitivity function for curvature detection has band-pass characteristics with respect to shape frequency. The shape of this function suggests that the curvature detection mechanism might consist of a set of sub-mechanisms each tuned for shape frequencies similar to mechanisms for contrast detection. In Experiment 1, we applied an adaptation for shape frequency to investigate whether shape frequency is the critical feature in curvature detection. We successfully replicated the U shape threshold function reported by Tyler (1973), but found that selective adaptation does not occur for shape frequency. These results suggest that shape frequency is not critical for curvature detection. In Experiment 2, we examined the possibility that curvature detection for the highest sensitivity range is mediated by a displacement process similar to that for Vernier acuity. The results indicate that curvature detection for this range is mediated by a mechanism that is sensitive to spatial displacement, and suggests the existence of a common mechanism for spatial displacement that mediates both curvature and Vernier detections. By comparing our results with those of several previous studies, we concluded that the apparent band-pass characteristic for curvature detection is produced by combining the characteristics of three separate limiting factors: local orientation at lower frequencies, spatial acuity at higher frequencies, and displacement in the highest sensitivity area.
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Eccentricity-dependent resolution losses are sometimes compensated for in psychophysical experiments by magnifying (scaling) stimuli at each eccentricity. The use of either pre-selected scaling factors or unscaled stimuli sometimes leads to non-monotonic changes in performance as a function of eccentricity. We argue that such non-monotonic changes arise when performance is limited by more than one type of constraint at each eccentricity. Building on current methods developed to investigate peripheral perception [e.g., Watson, A. B. (1987). Estimation of local spatial scale. Journal of the Optical Society of America A, 4 (8), 1579–1582; Poirier, F. J. A. M., & Gurnsey, R. (2002). Two eccentricity dependent limitations on subjective contour discrimination. Vision Research, 42, 227–238; Strasburger, H., Rentschler, I., & Harvey Jr., L. O. (1994). Cortical magnification theory fails to predict visual recognition. European Journal of Neuroscience, 6, 1583–1588], we show how measured scaling can deviate from a linear function of eccentricity in a grating acuity task [Thibos, L. N., Still, D. L., & Bradley, A. (1996). Characterization of spatial aliasing and contrast sensitivity in peripheral vision. Vision Research, 36(2), 249–258]. This framework can also explain the central performance drop [Kehrer, L. (1989). Central performance drop on perceptual segregation tasks. Spatial Vision, 4, 45–62] and a case of “reverse scaling” of the integration window in symmetry [Tyler, C. W. (1999). Human symmetry detection exhibits reverse eccentricity scaling. Visual Neuroscience, 16, 919–922]. These cases of non-monotonic performance are shown to be consistent with multiple sources of resolution loss, each of which increases linearly with eccentricity. We conclude that most eccentricity research, including “oddities”, can be explained by multiple-scaling theory as extended here, where the receptive field properties of all underlying mechanisms in a task increase in size with eccentricity, but not necessarily at the same rate.
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Accurately perceiving the activities of other people is a crucially important social skill of obvious survival value. Human vision is equipped with highly sensitive mechanisms for recognizing activities performed by others [Johansson, G. (1973). Visual perception of biological motion and a model for its analysis. Perception and Psychophysics, 14, 201; Johansson, G. (1976). Spatio-temporal differentiation and integration in visual motion perception: An experimental and theoretical analysis of calculus-like functions in visual data processing. Psychological Research, 38, 379]. One putative functional role of biological motion perception is to register the presence of biological events anywhere within the visual field, not just within central vision. To assess the salience of biological motion throughout the visual field, we compared the detectability performances of biological motion animations imaged in central vision and in peripheral vision. To compensate for the poorer spatial resolution within the periphery, we spatially magnified the motion tokens defining biological motion. Normal and scrambled biological motion sequences were embedded in motion noise and presented in two successively viewed intervals on each trial (2AFC). Subjects indicated which of the two intervals contained normal biological motion. A staircase procedure varied the number of noise dots to produce a criterion level of discrimination performance. For both foveal and peripheral viewing, performance increased but saturated with stimulus size. Foveal and peripheral performance could not be equated by any magnitude of size scaling. Moreover, the inversion effect––superiority of upright over inverted biological motion [Sumi, S. (1984). Upside-down presentation of the Johansson moving light-spot pattern. Perception, 13, 283]––was found only when animations were viewed within the central visual field. Evidently the neural resource responsible for biological motion perception are embodied within neural mechanisms focused on central vision.

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Spatial scaling of vernier acuity tasks

Abstract

Vision Research

Vision Research

Vision Research

Vision Research

Vision Research

Vision Research

Vision Research

Vision Research

Neuroscience

Vision Research

Vision Research

Vision Research

Vision Research

The sensations produced by electrical stimulation of the visual cortex

Journal of Physiology, London

Human cortical magnification and its relation to visual acuity

Experimental Brain Research

The representation of the visual field on the cerebral cortex in monkeys

Journal of Physiology, London

Magnification factor and receptive field size in foveal striate cortex of the monkey

Experimental Brain Research

The neural representaton of visual space

Nature

Neural substrates and threshold gradients in peripheral vision