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Stanley Govenlock, Allison Sekuler, Patrick Bennett; The effect of aging on the spatial pooling of local orientation signals. Journal of Vision 2009;9(8):1069. doi: 10.1167/9.8.1069.
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Pooling orientation information allows observers to perceive form and texture that extend beyond spatially-limited receptive fields. Additionally, pooling the activity of low-level units may help the visual system to overcome the effects of noise in individual mechanisms, and may be important for the integration of local orientation elements into contours (e.g., Wang & Hess, 2005), an ability that appears to be impaired among older observers (Roudaia et al., 2008). The current study used methods describe by Dakin (2001) to investigate whether the ability to pool orientation information across space declines with normal healthy aging. Nineteen younger (mean age=23) and 17 older (mean age=71) observers discriminated textures composed of 128 3-cpd Gabors (radius = 1 deg) that were positioned randomly within an annular field (inner and outer radii = 0.5 & 3.4 deg). The orientation of each Gabor was selected randomly from one of two Normal distributions with means of +/−M and a variance of s2. The task was to discriminate the mean orientation, and threshold (defined as 2M) was measured as a function of s2. Performance on this task depends on i) the accuracy with which the orientations of the texture elements are encoded, and ii) the efficiency with which information is pooled across elements. Hence, an effect of aging on local orientation coding or spatial pooling should alter the threshold-vs.-variance (TvV) curves. However, the TvV curves did not vary as a function of age (F(1,5)=1.49, p=0.22). This result extends previous studies showing that aging does not alter the perception of orientation for local contours (Betts et al., 2007; Delahunt et al., 2008; Govenlock et al., in press), and suggests that the spatial pooling of orientation is preserved in old age.
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