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Dov Sagi, Nitzan Censor; Global resistance to local perceptual adaptation in texture discrimination. Journal of Vision 2009;9(8):854. doi: 10.1167/9.8.854.
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© ARVO (1962-2015); The Authors (2016-present)
Intensive training or testing reduces performance on perceptual tasks (Censor, Karni & Sagi, 2006). These effects are specific to basic image features, implicating early stages of the visual stream rather than general fatigue (Mednick, Arman & Boynton, 2005; Ofen, Moran & Sagi, 2007). Recent results show that such adaptation-like performance decrements are practically eliminated following practice with a small number of trials and sleep (Censor & Sagi, 2008). This long-term learning effect suggests a link between perceptual deterioration and learning: best performance is achieved with short training while further training leads to decrements due to connectivity saturation. Resistance is achieved by sleep-dependent consolidation of unsaturated connectivity. Here we show that such training-induced resistance to perceptual decrements generalizes across retinal locations while effects due to extensive training were shown to be local. Texture stimuli were presented for 40 ms and backward-masked (Censor, Karni & Sagi, 2006). Observers decided whether an array of 3 diagonal bars embedded in an array of horizontal bars (19×19) was horizontal or vertical. In each session the target-mask SOA (stimulus onset asynchrony) decreased gradually to obtain a psychometric curve. Subjects practiced the texture discrimination task with 12 trials/block of SOA (~450 trials/session), showing low thresholds (133.4±6.7 ms, mean±SE), and returned for intense test-sessions with 50 trials/block (∼1600 trials/session) at both trained and untrained locations. Results showed that the average thresholds in the 50 trials/block test-sessions for both trained (138.8±6.7 ms) and untrained (139.8±7.5 ms) locations were significantly lower than those of na?ve subjects trained with 50 trials/block (184.9±14.0 ms). Further experiments revealing the different transfer properties of performance decrements and increments allow us to identify local and global components of perceptual learning and their interactions, suggesting mechanisms that induce modifications of higher brain areas which interact with local early visual networks and enable improvement of perceptual abilities.
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