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Preeti Verghese; Self-cueing contributes to contour detection in noise. Journal of Vision 2002;2(7):191. doi: 10.1167/2.7.191.
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© ARVO (1962-2015); The Authors (2016-present)
We have shown previously that the ease of detectability of an extended trajectory in noise is because the first segment of the trajectory acts as an automatic cue, alerting the motion system to subsequent segments of the trajectory. This study investigates whether such a self-cueing process also increases the detectability of static paths in noise. Current research suggests that the detectability of static contours in noise is due to long-range interactions among neurons with similar orientation preference, and to a contrast normalization process that preferentially pools collinear signals. In addition, the cue provided by collinear elements may be a strong component of contour detectability. If the contour cue acts in a similar manner as an explicit cue, it might increase the response gain of similarly oriented elements in the vicinity, and/or reduce the number of potential locations (uncertainty) that the observer monitors. To assess the strength of the contour cue, I measured sensitivity to contrast increments on a test patch placed at various offsets relative to the cueing contour. Noise density and the length of cueing contour were also manipulated. Signal detection theory analysis of the psychometric function provided estimates of the gain and uncertainty parameters associated with each condition. In the presence of noise, observers were best at detecting a contrast increment on a patch that was aligned with the cueing string, but the gain decreased with increasing offset from the aligned position. The estimate of uncertainty at a given noise level did not change with offset, but uncertainty decreased significantly when the length of the cueing string was increased. The high gain for collinear test patches and the ability of the contour to reduce uncertainty at high noise densities is indeed similar to the effect of an explicit cue (e.g., Lu & Dosher, 1998), suggesting that self-cueing contributes to the detectability of contours in noise.
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