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Kilho Shin, Bosco S. Tjan; Crowding with invisible flankers – a reexamination. Journal of Vision 2013;13(9):578. doi: 10.1167/13.9.578.
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© ARVO (1962-2015); The Authors (2016-present)
Crowding is a key limiting factor of form vision in the periphery. The neural origin of crowding is unclear. How awareness of flankers affects crowding can inform the origin of crowding. However, results in the literature appear conflicting. Gratings rendered invisible by interocular suppression (IOS) produce crowding (Ho et al., 2011; Shin & Tjan, 2011 VSS); letters rendered invisible by adaptation-induced blindness (AIB) do not (Wallis et al., 2011). We re-examined these findings while eliminated stimulus difference as a factor. We rendered flankers invisible with IOS in Exp1 (gratings) and Exp2 (letters), and with AIB in Exp3 (gratings). In Exp1 and 2, we presented a target with up to 4 flankers to the non-dominant eye and four high-contrast dynamic concentric checkerboards to the dominant eye to suppress the flankers. Subjects discriminated orientations (clockwise/counter-clockwise) in Exp1 and identified letters in Exp2. They also reported the number of visible flankers. In Exp3, we presented 4 gratings (adaptors) at the flanker locations preceding flanker presentation (1 min initial and 5 s top-up adaptation). The orientations of adaptors were randomized within twice the subject’s orientation threshold and jittered at 10 Hz. Tasks were the same as Exp1. We found that the accuracy of target identification decreased as the number of physical flankers increased when the flankers was rendered invisible by IOS (Exp1 and 2). However, in the case of AIB (Exp3), performance depended on the number of subjectively visible flankers. Our results are consistent with the literature but have eliminated stimulus difference as a factor. These findings imply that crowding starts before the neural locus of IOS and after that of AIB, and place the neural origin of AIB before that of IOS. Our results is consistent with the view that crowding starts as early as V1 and is exacerbated in higher visual areas.
Meeting abstract presented at VSS 2013
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