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Dave Ellemberg, Aaron Johnson, Bruce Hansen; The development of natural image contrast sensitivity. Journal of Vision 2008;8(6):346. doi: 10.1167/8.6.346.
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© ARVO (1962-2015); The Authors (2016-present)
The present study verified the hypothesis that the development of contrast sensitivity to the spatial frequency content of natural images extends beyond the development of contrast sensitivity when tested with luminance modulated sine-wave gratings. In the same group of children and adults, we compared contrast sensitivity with a series of natural images for which a specific slice of spatial content was removed (a narrow range of à values) and we also tested contrast sensitivity with a series of sine-wave gratings varying in spatial frequency. Thresholds were measured with a temporal forced-choice task combined with a QUEST staircase procedure. Our data show that for children and adults, detection thresholds for natural images were increased by the removal of spatial content and the shift in threshold was dependent on the spatial frequencies removed. Indeed, thresholds were most elevated when the frequencies removed were those that the visual system is most sensitive to. This suggests a close relationship between spatial frequency processing and natural image perception. However, unlike grating contrast sensitivity, which becomes adult-like at each frequency tested by about 7 years of age, contrast sensitivity for natural images only becomes adult-like by about 10 years of age. Further, sensitivity matures less rapidly for lower frequency filtered natural images than for the higher frequency filtered natural images. Together, these results indicate that the mechanisms involved in the processing of the spatial frequency content of natural images mature less rapidly than specific mechanisms tuned to a single spatial frequency and orientation. Finally, because of the important developmental differences between traditional contrast sensitivity compared to natural image contrast sensitivity, the latter might be a more ecologically relevant way assess the limits of visual perception in children and in individuals with a visual pathology.
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