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Ariella V. Popple, Dennis M. Levi, Stanley Klein; Popout templates in amblyopic observers vary with eye-of-origin. Journal of Vision 2002;2(10):136. doi: 10.1167/2.10.136.
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Observers are able to indicate the approximate location of a briefly flashed popout target in an array, but make frequent errors toward neighbors of the target (Gilchrist et al., 1999; Solomon & Morgan, 2001; Popple & Petrov, 2002). These neighbor-errors can be used to reconstruct the ‘template’ for target localization. We presented such arrays monocularly, followed after 83 ms by an array of masks. Stimuli were 5.5 cpd Gabor patches, with envelope sd 5.5 min arc. The target was horizontal from verticals, or vertical from horizontals, presented in separate blocks. Arrays were 3×3 (4.4° spacing), 5×5 (2.2° spacing), 9×9 (1.1° spacing) or 17×17 (0.55° spacing). Observers indicated the target location with a mouse-pointer. To ensure accurate central fixation, each trial was initiated by clicking on the central mask patch. Using reverse correlation, we computed where the target needed to be in order to elicit a response at a given location. Monte-Carlo simulation can be used to distinguish between response bias and biases in template structure. These templates varied according to array density and response location, but were almost invariant with eye-of-origin for four normal observers, although overall performance was poorer in the non-preferred eye. In contrast, preliminary data from a strabismic amblyope reveal biased templates in the amblyopic eye, despite training to normal isolated-letter acuity. Our paradigm allows us to characterize whether this bias is due to pure topographical noise, or is dependent upon effects of spatial context such as the stimulus array density.
Gilchrist, I. D., Heywood, C. A., & Findlay, J. M. (1999). Saccade selection in visual search: evidence for spatial frequency specific between-item interactions. Vision Res. 39, 1373–83.
Solomon, J. A., & Morgan, M. J. (2001). Odd-men-out are poorly localized in brief exposures. Journal of Vision, 1(1), 9–17.
Popple, A. V., & Petrov, Y. (2002). The shape of pop-out depends on stimulus density, location and orientation. Vision Sciences Society, S530.
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