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Joshua L. Wede, Gregory Francis; The role of selective visual attention in the formation of visual afterimages: Experimental data and model simulations. Journal of Vision 2006;6(6):601. doi: 10.1167/6.6.601.
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© ARVO (1962-2015); The Authors (2016-present)
Suzuki & Grabowecky (2003) reported that a negative afterimage appeared later and was weaker when attention was focused on the inducing stimulus. We explored the effect of attentional focus on afterimages formed by a sequence of two inducing stimuli. After viewing two successive orthogonal bar gratings, observers frequently report an afterimage of the first grating. We explored the effect of directing attention on the first stimulus (S1 - vertical bars) and the second (S2 - horizontal bars) by measuring the proportion of reported vertical afterimages. Subjects either attended to a feature of the inducing gratings (bar changing colors) or attended to centrally presented, rapidly changing numbers. Results show that when subjects attended features of S2, they reported a higher percentage of vertical afterimages. Thus, attentional focus on the inducing stimuli increased afterimage strength. Both sets of experimental results were interpreted in terms of Grossberg's FACADE model (Grossberg, 1994). In this model, an afterimage results from interactions between color complement after-responses from a Feature Contour System (FCS) and orientation after-responses from a Boundary Contour System (BCS). Previous results, and the current experiment suggested attention enhances signals in the BCS. With negative afterimages, increasing attention on the BCS signals leads to a mismatch between orientation after-responses and color after-responses, delaying afterimage appearance. In the two-stimulus case, attentional focus on S2 increases the strength of orientation after-responses that match the arrangement of color after-responses generated by the S1. Model simulations demonstrate that the model explains both sets of data.
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