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Leslie Krause, Jennifer Anderson, Michael Levine, E. Leslie Cameron; Visual Performance Fields in Motion. Journal of Vision 2016;16(12):225. doi: https://doi.org/10.1167/16.12.225.
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© ARVO (1962-2015); The Authors (2016-present)
Visual performance fields are inhomogeneous. Performance is better on the horizontal than the vertical meridian (Horizontal Vertical Anisotropy (HVA)) and is often better in the lower visual field (Vertical Asymmetry (VA)). Performance is particularly poor on the vertical meridian above the point of fixation (the north effect), and sometimes, below the point of fixation (the south effect). Visual field inhomogeneities are primarily explored using stationary stimuli, such as Gabor patches and inhomogeneities become more pronounced as spatial frequency (SF) increases. Relatively few studies have described visual field inhomogeneities using moving stimuli and none have explored the effect of SF. This study examined visual field inhomogeneities with drifting Gabors at 4 SFs (0.5-8cpd). Five participants performed a 2AFC direction discrimination task with 1 degree Gabors drifting at 4 Hz. Stimuli were presented at one of 8 equally-spaced target locations, at 4.5 deg eccentricity. Visual field inhomogeneities were quantified by fitting data with hemi-ellipses (see Anderson, Cameron & Levine, 2014). An HVA was observed at all SFs. Surprisingly, a VA was not observed. In fact, performance was better in the upper visual field at all SFs except the 0.5cpd condition. A north effect was observed at all SFs with the exception of 0.5cpd and a trend for a south effect emerged at 2 and 4cpd, but was not evident at 0.5 and 8cpd. In a control study a north effect was observed at low SF when the target size was doubled (i.e., more cycles in the Gabor). These results suggest that the ability to detect direction of motion is similar to the ability to detect orientation. Both capabilities may depend on a more primitive detection process at some earlier processing stage.
Meeting abstract presented at VSS 2016
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