Abstract
Visual system is known to restore missing information at the blind spot using the information surrounding the blind spot (monocular information) as well as the information represented in the opposite eye (binocular information). To understand the mechanism of filling-in process, we compared the quality of the surface perception resulting from monocular (Experiment 1) and binocular (Experiment 2) filling-in process. Experiment 1 tested whether the same effect of collinearity and orientation differences on contour integration was observed at the blind spot. We presented two separate bars, a reference at the one edge of the blind spot and a test bar at the opposite edge, constituting various angles. The bars contained gratings collinear or orthogonal to their orientations. Participants' task was to report the minimum length of the test bar yielding perceptual connection between the two bars. The test bar filled in the blind spot with shorter length when the gratings were collinear and the two bars were straighter, implying that the filling-in process engages the same contour-integration mechanism. Experiments 2 investigated whether this filled-in surface differed from physical surface by comparing the amount of interference effect from filled-in and physical surface. Dot patterns were presented either around the blind spot, corresponding location in the opposite eye, or both, so to interfere with detection of a small dot appearing in the opposite eye in location corresponding to the blind spot. Detection performance was the best when only filled-in surface was presented as an interference pattern comparing to the same interfering stimuli presented to non-blind-spot area, suggesting that perceptual quality in filled-in surface is not identical to that in physical surface. In sum, though filling-in process in the blind spot share common filling-in mechanism, the resulting percept does not correspond to that from physical reality.
This work was supported by the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea government(MOST) (No. R01-2008-000-10820-0).