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Lindsay E. Farber, Allison B. Sekuler, Patrick J. Bennett; The effects of aging on surround modulation of backward contrast masking. Journal of Vision 2010;10(7):1397. doi: 10.1167/10.7.1397.
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Saarela and Herzog (J Vis, 2008, 8(3):23, 1-10) measured backward masking for a centrally-viewed Gabor target that was produced by a small central mask that overlapped the target, a surround annulus mask, and a large combination mask (i.e., centre plus surround). Interestingly, they found that significantly less masking was produced by the combined mask than the central mask, even though the surround mask produced little masking on its own. One interpretation of this result is that the surround reduced the effectiveness of the central mask. The current study examined whether this non-linear interaction between centre and surround masks is affected by aging. Detection thresholds were measured for a Gabor target (duration=80 ms) in five younger (∼25 years) and older (∼69 years) subjects. The target was preceded or followed by surround, central, or combination masks. Thresholds were measured using surround, central, and combination masks that were displayed for 200 ms at five SOAs relative to target onset. The target and masks were 4 cpd and had a horizontal orientation. Mask contrast was 0.4; a baseline, no-mask condition also was included. Significant masking was obtained in both age groups, and the combined mask produced less masking than the central mask. However, the temporal pattern of masking across target-mask SOA differed noticeably between groups. Our results suggest strong centre-surround interactions exist in older subjects, but that the temporal properties of these interactions change with age.
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