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Masato Sakurai, Kathy T. Mullen; Cone weights for the cone opponent detection mechanisms in human peripheral vision. Journal of Vision 2006;6(6):232. doi: https://doi.org/10.1167/6.6.232.
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© ARVO (1962-2015); The Authors (2016-present)
Aims: To determine whether there are any changes between foveal and peripheral vision in the L, M and S-cone weights for the two cone opponent chromatic mechanisms (red-green and blue-yellow).
Methods: We measured detection threshold contours in three different planes in 3-d cone contrast space, chosen to best reveal the cone weights to the two chromatic mechanisms: the L/M plane, the (L+M)/S plane, and the isoluminant plane (L−xM)/S. Thresholds were measured for foveal and peripheral stimuli (15 or 20 degs in the nasal field). Stimuli were spatio-temporal Gaussian “blobs” on a gray background (49.7 cd/m2) with a spatial sigma fixed in the horizontal meridian (0.5 deg), and variable in the vertical meridian (0.5–1.8 deg, scaled by the cortical magnification factor). To suppress the increased contribution of the luminance mechanism relative to the chromatic mechanisms in peripheral vision, achromatic masking noise (2-d, dynamic) was added to the test stimulus when measuring in the L/M and L+M/S planes in the periphery. Detection thresholds were measured using a 2AFC staircase procedure in three normal subjects.
Results: Detection thresholds were fitted by ellipses in each plane at each eccentricity. Comparisons of the orientations of the ellipses between fovea and periphery show no consistent changes with eccentricity across subjects.
Conclusions: Cone weights for the foveal mechanisms support those of previous studies (Sankeralli and Mullen, JOSA A, 1996). Our results indicate that cone weights for the red-green and blue-yellow chromatic mechanisms are invariant up to 20 deg in the nasal visual field.
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