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D.K. Freeman, C.L. Passaglia, J.B. Troy; Effect of Peripheral Gratings on Human Grating Acuity . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3769.
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© ARVO (1962-2015); The Authors (2016-present)
Investigate the effect of a peripherally–located grating on the spatial contrast sensitivity of human observers to a centrally–located grating.
Subjects were positioned 60cm from a 30x40cm video monitor at eye level and their gaze was directed at a fixation point in the center of the monitor display. A stimulus consisting of two independent sinusoidal drifting gratings was then presented to the subject in a 2AFC paradigm. One of the gratings subtended the central 10 deg of the display and the other grating covered the remainder of the display. The subject’s task was to identify in which of two consecutive intervals of 1–sec duration the central grating was displayed. For one set of measurements the peripheral grating was present and for another it was not. For both conditions, contrast threshold was determined by manipulating the contrast of the central grating from trial–to–trial using a 3down–1up staircase procedure. Contrast thresholds were measured for central gratings of a range of spatial frequencies drifting at 2Hz. The peripheral grating was fixed at 50% contrast and was either 0.1cyc/deg and 4Hz (LSF/HTF) or 2cyc/deg and 0.2 Hz (HSF/LTF).
Contrast thresholds for the central grating were unaffected by the HSF/LTF peripheral grating but were significantly elevated in the presence of the LSF/HTF grating. The loss in sensitivity was most evident for central gratings of low spatial frequency.
The responses of mammalian retinal ganglion cells to stimuli within their receptive field are known to be modulated by stimuli outside it. The effect of peripheral gratings on human spatial contrast sensitivity resembles the effect of these gratings on ganglion cell spatial tuning curves, suggesting that this aspect of perceptual contrast adaptation has a retinal component.
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