Abstract
The spatial properties of rod-cone interaction was investigated with a 2-channel 4-primary Maxwellian view system . Rod and cone isolating stimuli were generated using the method of silent substitution. Detection thresholds for a 100 ms 1 deg diameter rod pulse were measured at different phases of a 0.5 Hz cone-modulating background. The background was modulated either along L+M luminance or L−M chromatic axis, and it covered 1) a 1 deg diameter field same as the test, 2) a 12 deg diameter large field, or 3) an annulus surrounding the test (1 deg inner diameter and 12 deg outer diameter). The stimulus was presented at 6 deg extra-foveal (nasal). The mean luminance was either 200 photopic td (98 scotopic td) or 20 photopic td (9.8 scotopic td). The mean chromaticity was (0.8, 0.33. 0.67) in (s, m, l) coordinate. Results show that rod thresholds are clearly modulated by the cone-modulating background, and the interaction is mainly local; the effect of lateral cone modulation on rod threshold is weak. This is consistent with rod thresholds being mediated by rod signals converged to the cone pathway via rod-cone gap junction. The overall influence of L-M chromatic carrier on rod threshold is weaker than L+M luminance carrier, which is consistent with weaker rod inputs to parvecellular pathways than magnocellular pathways (Lee., Smith, Pokorny, & Kremers, 1997).
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We thank Joel Pokorny and Jules Quinlan for building the Maxwellian view system, and thank Dingcai Cao and Linda Glennie for supports in software. This work is supported by the Norwegian Research Council Grant No.176541/V10 and 182768/V10.