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Allison Sekuler, Jordan Lass, Ali Hashemi, Patrick Bennett, Mary Peterson; Aging alters neural processing underlying figure-ground organization. Journal of Vision 2017;17(10):305. doi: 10.1167/17.10.305.
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Aging decreases observers' ability to segment figure from ground, but what neural mechanisms underlie age-related changes in figure-ground organization? We measured EEG in older and younger observers while they viewed stimuli comprising eight alternating convex and concave regions, and indicated whether a red probe was "on" or "off" the region they perceived as figure. There were two types stimuli: (1) high-competition stimuli, in which all convex regions were one colour and all concave regions were a different colour; these stimuli support two competing interpretations: convex or concave figures in front of a ground of uniformly coloured regions of the other type; (2) low-competition stimuli, in which all concave regions were the same colour, but convex regions were each coloured differently, favouring the interpretation of convex figures of varying colours in front of a uniformly coloured background comprising concave regions. In younger observers, the amplitude of the parieto-occipital N250 event-related potential (ERP) was more negative for high- than low-competition stimuli. This difference was absent in older observers. Furthermore, the N250 amplitude difference was inversely correlated with behaviour: Individuals showing a larger N250 difference between high- and low-competition stimuli reported seeing the convex regions as figures equally often in high- and low-competition stimuli, whereas individuals with similar N250 amplitudes across conditions were less likely to perceive convex regions as figure in high- than low-competition stimuli. The brain-behaviour correlation also separated observers by age: Older observers generally showed a large behavioural difference between high- and low-competition conditions, but smaller ERP differences; whereas younger observers generally showed a small behavioural difference, but larger ERP differences. These results suggest that figure-ground organization is driven by mechanisms sensitive to the degree of competition between stimulus interpretations, and that the age-related reduction in resolving high figure-ground competition in healthy aging is related to an altered neural response.
Meeting abstract presented at VSS 2017
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