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Y-Z Wang, CE Wilson; Global Visual Integration in Aging . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4790.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Recent results obtained from young adults suggest that detection of deviation from circularity introduced by radial deformation may involve global visual integration over the area covered by the stimulus. In this study, we investigated the ability of senior adults to integrate this visual information. Methods: Eight experienced normal senior subjects (mean age 69 years) and three normal young subjects (mean age 36 years) participated in the study. Stimuli were circular D4 (CD4) contours with partial or full radial modulation. The D4 peak spatial frequency was 3 cyc/deg; the radial modulation frequency was 8 cyc/360 deg and mean radius was 1 deg. A partially modulated CD4 contour had only one modulation cycle (local perturbation from smooth curvature), while a fully modulated CD4 contour had 8 modulation cycles (radial frequency pattern). A temporal 2AFC staircase paradigm was employed. Thresholds for detecting the radial deformation were estimated by a maximum likelihood fitting procedure. Results: For senior subjects, the average threshold for detecting full radial modulation was 9.5±0.8 (SEM) arcsec, which was significantly lower than the mean threshold of 25.2±2.3 arcsec for detecting localized perturbation from circularity (one cycle of radial modulation) (t≷6.5, p<0.0001). The detection threshold for full radial modulation was also significantly lower than the threshold value of 12.6 arcsec, predicted by probability summation based on a purely local mechanism (p<0.05). When compared with young subjects, senior subjects showed significant loss (2-fold) in sensitivity for detecting localized deviation from circularity (p=0.0132), but demonstrated no significant difference in detecting full radial deformation (p=0.331). Conclusion: The differential effects of aging on local and global visual processing are consistent with the hypothesis that a local visual processing mechanism alone cannot account for the optimal performance in detecting radial deformation. Moreover, the stability of global radial deformation thresholds with age suggests that this task may be more effective than a local task to quantify the visual loss caused by age-related eye disease.
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