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Laure Saint-Aubert, Florence Rémy, Nadège Bacon-Macé, Emmanuel Barbeau, Nathalie Vayssière, Michèle Fabre-Thorpe; Rapid visual categorization of objects in natural scenes: the “contextual effect” is strengthened by aging. Journal of Vision 2011;11(11):821. doi: 10.1167/11.11.821.
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© ARVO (1962-2015); The Authors (2016-present)
The processing of objects embedded in an incongruent context, is impaired in accuracy and speed. This “contextual effect” is observed even when top-down influences are minimized by using rapid visual categorization of briefly flashed scenes. This effect could result from feed-forward interactions between selective populations of visual neurons: facilitation (interference) would result from habitual (conflictual) co-activations. In the present study, we investigated whether the size of the contextual effect was modulated as a function of age. We tested 87 subjects (20–91 years old) in a two forced-choice rapid categorization task. Images containing either an animal or a piece of furniture in congruent or incongruent context were briefly flashed on a screen. Participants were asked to categorize the object by responding as fast as possible using two buttons (each button being assigned to one category). Performance was analyzed separately depending on age. Four groups were considered: 20–30; 45–55; 60–75 and over 75 years old. A bank of images was specifically created for this task, with objects of variable size (mean size = 12.7 ± 4.7% of total pixels) as an anticipation to tackle pathological aging, and a strict control of luminance, contrast, object size and localization. As already reported, contextual incongruence impaired object categorization in both accuracy (p < 0.001) and response speed (p < 0.001). The present study shows that this effect increases progressively with age (p < 0.001 for accuracy and p < 0.01 for speed). Comparing performance on congruent vs incongruent stimuli in the youngest and the oldest group, the drop of accuracy increased from 1.5% to 7% and the mean reaction time from 12 ms to 30 ms. Inhibitory or facilitatory co-activations between visually selective populations of neurons are expected to be built from experience. The enhancement of the contextual effect in healthy aging could be due to a lifetime of experience with the surrounding world.
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