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Nestor Matthews, Kei Kurosawa, Kristen Strong; Hastening orientation sensitivity. Journal of Vision 2006;6(6):157. doi: https://doi.org/10.1167/6.6.157.
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© ARVO (1962-2015); The Authors (2016-present)
Previous perceptual learning studies have shown that sensitivity to subtle orientation differences improves with practice at oblique axes, but not with practice at cardinal axes. The cause of this anisotropy in angular resolution is uncertain, and it is not known whether the same anisotropy pertains to temporal resolution -the minimum stimulus duration needed to achieve a specified angular resolution. Here, we investigated the hypothesis that practice effects at cardinal axes had previously not occurred because there had been little or no internal noise in the visual response to cardinal orientations. Accordingly, we exploited the internal noise that occurs naturally when masked stimuli are presented for extremely brief durations. After 110,000 trials were completed over seven daily sessions, temporal resolution improved by 51% at cardinal axes, and by 86% at oblique axes. This hastening of the visual response was accompanied by significant improvements in angular resolution that were specific to the cardinal axis in the cardinal training group, and the oblique axis in the oblique training group. The data demonstrate plasticity in the response to cardinal orientations, and support the hypothesis that sufficient levels of internal noise are necessary for perceptual learning.
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