Filling-in and contour adaptation S Anstis |
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Psychology, UCSD, CA, United States
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| Contour adaptation (CA) is a novel aftereffect. Following adaptation to a thin, flickering outline circle, the whole of a congruent low-contrast disk disappears from view for several seconds. Thus CA can temporarily erase edges, allowing the background grey to fill-in the area of the disk. This suggests that luminance information is stored in edges and contours and propagates inwards from them. CA erases only luminance edges, not colored edges, and it shows no interocular transfer, so it probably arises early in the M pathways. It halves the perceived contrast of medium-contrast test disks, and pushes low-contrast test disks below threshold so that they disappear entirely. A peripherally viewed grey square superimposed on low-contrast horizontal stripes is clearly visible. But adaptation to a thin outline flickering square makes the grey test square become invisible, so now the stripes appear to extend continuously across the position of the square. This CA-induced “filling-in” models the filling-in of the natural blind spot, and of acquired scotomata in glaucoma or Stargardt’s disease. CA may help to clarify whether such filling-in is passive (Dennett 1991) or active (Churchland & Ramachandran 1995). Supported by a grant from BaCaTec. |
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