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Nathaniel Douda, Jamie Opper, Vicki Volbrecht; Changes in peripheral saturation with increasing stimulus duration and background luminance. Journal of Vision 2013;13(15):T27. doi: 10.1167/13.15.27.
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© ARVO (1962-2015); The Authors (2016-present)
Rods have been implicated as contributing to the desaturation of stimuli at mesopic levels in the peripheral retina; yet, as stimulus size increases, stimuli appear more saturated despite the activation of more rods. This finding suggests that increased cone activity with stimulus size is inhibiting rod activity. This study investigated the perception of saturation for a large stimulus (4.3°) at 10° temporal retinal eccentricity and the effect of rods, if any, on it. We explored the interactions of stimulus duration (10 to 1000 ms), background luminance (−2.5 to 1.0 log td), and wavelength (400 to 640 nm) on perceived saturation for a 20 td stimulus known to fill the perceptive fields of the four elemental hues at 500 ms. The ‘4+1’ hue-naming procedure was used. Results showed an increase in percent saturation as stimulus duration and background luminance increase. The saturation function became “flatter” in the area of the visible spectrum traditionally associated with a saturation minimum (520–580 nm). This effect was particularly pronounced for shorter durations when comparing the no-background condition to background conditions above (1.0 log td) and below (−2.5 log td) cone threshold. These results suggest that stimulus parameters that strengthen chromatic responses (i.e., longer stimulus duration) and reduce rod activity (i.e., higher background luminances) improve our perception of peripheral chromatic stimuli, particularly in the middle-wavelength portion of the spectrum. Stimuli may appear more saturated in the peripheral retina than the fovea given the loss of the saturation minimum in the middle-wavelength portion of the spectrum.
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