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B. M. Sheliga, C. Quaia, L. M. Optican, E. J. FitzGibbon; Spatial summation properties of the human ocular following response (OFR): Dependence upon the spatial frequency of the stimulus. Journal of Vision 2011;11(11):526. doi: https://doi.org/10.1167/11.11.526.
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© ARVO (1962-2015); The Authors (2016-present)
We recorded initial OFRs of three human subjects when 1D vertical sine-wave gratings were subject to horizontal motion in the form of successive 1/8-wavelength steps (20 Hz temporal frequency). The gratings occupied a single horizontal strip whose height was systematically varied from 0.15° up to the full screen (36°). The strip was always centered vertically at a subject's eye level and extended the full width of the display (47°). The magnitude of the OFRs was calculated as a change in eye position over the initial open-loop period measured with respect to response onset. All gratings had a fixed contrast of 32% while their spatial frequency (SF) ranged from 0.03 to 2 cpd. Increasing the strip height led to a SF-dependent reduction in the OFR latency: the reduction was minimal (or even absent) for the highest SFs and maximal (up to 50 ms) for the lowest SFs. Since raising the height of the strip resulted not only in an increase in the total area covered by the grating, but also in a concomitant stimulus extension towards more and more peripheral portions of the visual field, we showed in a subsequent control experiment that the OFR latency reduction was due to the former but not the latter factors. The magnitude of the OFRs grew monotonically while the strip height was increased up to a certain level – the optimal height (OH). Increasing the strip height beyond OH led to response attenuation. The OH was in the range of 1–3° for the highest SFs and 18–36° for the lowest. With very few exceptions, the OH versus SF relationship was close to linear with negative slope when plotted on a log-log scale. We will discuss if differences in the spatial distribution of relevant motion detectors and their interactions could account for the observed SF dependencies.
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