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Lindsay E. Farber, Allison B. Sekuler, Patrick J. Bennett; The effect of mask contrast on spatiotemporal masking in younger and older subjects. Journal of Vision 2011;11(11):1181. doi: 10.1167/11.11.1181.
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Although there is evidence for weaker centre-surround interactions in older subjects in tasks using dynamic stimuli (Betts et al., Neuron, 45(3), 361-6, 2005; Betts et al., J Vis, 9(1):25, 1–15, 2009), the effect of the surround is much stronger for older adults in tests of perceived contrast (Karas et al., J Vis, 9(5):11, 1–9, 2009). Previously, we measured detection thresholds for a horizontal 3.5 cycles-per-degree Gabor target masked by a small central sine wave mask, a surround sine wave annulus, and a combination mask (centre-plus-surround) of the same spatial frequency. Target onset, relative to the 40% contrast mask, varied across conditions. The shapes of the overlay masking functions obtained from younger and older subjects were similar to those found for young subjects by Saarela and Herzog (J Vis, 8(3):23, 1–10, 2008), but the overall level of masking was lower in older subjects. One potential explanation for this age difference is older subjects had lower contrast sensitivity for the mask. The current experiment tests this hypothesis by measuring masking functions with different mask contrasts ranging from 10% to 80%. We found that varying contrast had different effects on masking in younger and older subjects, and that the age difference could not be explained by a difference in contrast sensitivity. Our results suggest that the relative strength of age-related changes in centre-surround interactions depend on the spatiotemporal properties of the stimulus.
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