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Stockman, Elizabeth Crowther, Caterina Ripamonti; Silent surrounds: the M-cones gate the S-cone input to luminance. Journal of Vision 2007;7(15):108. doi: 10.1167/7.15.108.
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© ARVO (1962-2015); The Authors (2016-present)
Under conditions of intense long-wavelength adaptation, the S-cones make a small, but robust contribution to luminance, as defined by heterochromatic flicker photometry. The extent to which this contribution persists under other conditions of adaptation, however, remains unclear. Here, by using selective adaptation and/or tritanopic metamers to isolate the S-cone response, we investigate the dependence of the S-cone luminance input on changes in background wavelength and background radiance. Remarkably, the S-cone luminance input disappears completely when no adapting background is present, even though the same S-cone stimulus makes a clear contribution to luminance in the presence of a long-wavelength background. The dependence of the S-cone luminance input on the wavelength and radiance of the adapting background is also surprising: We find that the S-cone signal can only be measured on fields of 543 nm and longer that exceed a criterion background radiance. These criterion radiances follow an M-cone spectral sensitivity, which suggests that the S-cone luminance input is silent unless the M-cones are also excited above a certain level. Our results suggest that the S-cone luminance signal is somehow gated by M-cone signals, a finding that is reminiscent of the silent chromatic surrounds suggested by Ingling and his co-workers.
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