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Allison McKendrick, Anne Weymouth; The effects of aging on low and intermediate stages of form processing. Journal of Vision 2011;11(11):465. doi: https://doi.org/10.1167/11.11.465.
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© ARVO (1962-2015); The Authors (2016-present)
This study explored the effects of healthy aging on the early stages of the processing of contours and shapes. Forty-two adults participated. Participants were divided into three groups: 16 young adults (19 to 34 years, mean = 27); 12 middle aged adults (40 to 59 years, mean = 50); and 14 older adults (63 to 73 years, mean = 66). Four visual tasks were employed: 1) collinear facilitation for 3 c/deg Gabor patches; 2) contrast-contrast spatial surround suppression (Chubb illusion) where contrast matching thresholds were measured for a 40% contrast, 4 c/deg sinusoidal grating circular patch (0.67 deg radius) in the presence and absence of a 95% contrast grating annulus (4 deg radius); 3) a contour integration task involving discriminating an elliptical global contour from a circular contour in noise; and 4) Glass pattern coherence thresholds. Compared to young adults, the older group showed: a reduced strength of collinear facilitation (p < 0.05); an increased magnitude of surround suppression for the centre-surround task (p < 0.05); elevated aspect ratio thresholds for the detection of the elliptical contour in noise (p < 0.05); and elevated Glass pattern coherence thresholds (p < 0.05). There was also a trend for older observers to require closer spacing between contour elements within the contour integration task (p = 0.07). Mean thresholds for the middle aged adults fell between those of the younger and older groups for all tasks. Effect sizes (Cohen's d) were calculated to compare the aging effects between tasks: collinear facilitation: 0.8; surround suppression: 1.9; global contour integration: 0.8; Glass pattern coherence thresholds: 0.9. Overall, the results show that normal aging alters performance for a range of low through intermediate form processing tasks, with the largest effect being a substantial increase in the suppression of apparent contrast by the presence of a high-contrast annular surround.
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