Abstract
fWhen an object passes through a narrow slit, even though only a small fragment of the object is seen at a given moment, the object can still be perceived as a whole. Little is known about how our visual system temporally integrates fragmented images at the same retina location. As an important constituent of visual object is visual contour, here we examined whether and how discrete contour elements could be temporally integrated under slit-viewing.
Visual contours composed of Gabor patches and embedded in a background of randomly oriented Gabors were moved behind a vertical slit. The contour elements were either parallel (‘snake’), orthogonal (‘ladder’), or at 45 deg (‘acute’) to the contour path. A temporal 2AFC method of constant stimuli was used to measure contour detection performance.
We found that: (1) In the ‘snake’ configuration, even though the slit was narrower than the average distance between neighboring Gabors, the embedded global contours could be reliably detected with an inter-element angle difference up to 20 deg and within a broad range of moving speeds up to 13 deg/s. (2) Contour detection was independent of the spatial phase (in-phase or out-of-phase) of contour elements, excluding the possibility of temporal luminance summation by single spatial filters. (3) ‘Snake’ paths under slit-viewing were much easier to detect than orthogonal and acute paths.
Our study indicates that the Gestalt rule of continuity governing spatial interaction in full-field viewing still applies to temporal integration under slit viewing. This suggests that the contour-related information under slit-viewing can be extracted locally by an ensemble of visual neurons whose responses are modulated by recent stimulus history, and that long-range collinear interactions are not a unique mechanism in linking visual contours.