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K.G. Young, R.W. Li, D.M. Levi, S.A. Klein, E.Y. Huang; Interocular transfer in perceptual learning of a Vernier task . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4363.
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Purpose: Our previous work suggests that perceptual learning of hyperacuity is both orientation and eye–specific if the untrained eye was patched. We hypothesize that this monocular learning is learning to see through rivalry (learning to ignore the patch). This hypothesis predicts that learning will transfer from the trained eye to the untrained fellow eye under conditions where the observer does not know the eye–of–origin (utrocular conditions). Methods: To test this hypothesis we used a mirror haploscope to present one screen to one eye and the other to the fellow eye. The Vernier stimulus was comprised of two segments with a 7.5 minute gap between the two segments. Each segment consisted of five high contrast (84%) Gabor patches (carrier SF, 10cpd), with 5 minutes of arc separation in between each patch. The experiment consisted of three phrases: pretraining and post–training measurements of the horizontal and vertical Vernier thresholds for each eye; a training phase in which observers repetitively trained on a horizontal Vernier task in the left eye and a vertical Vernier task in the right eye. The left and right eye stimuli were randomly interleaved, and the observer was unaware of which eye was being stimulated. Each observer completed 4000 trials by the end of the experiment. A rating–scale signal detection paradigm was used to measure thresholds for discriminating the direction of offset. We tested 12 novice normal observers with visual acuity of 20/20 or better. Results: We found significant improvement in Vernier acuity in both the trained and untrained orientations. There was 21.1±4.6% mean improvement in the trained eye and 23.9±4.7% mean improvement in the untrained eye. There was no statistically significant difference in mean improvement between the trained and untrained eyes (paired t=0.5242, p=0.6052), suggesting that there was complete interocular transfer of the learning effect. Conclusions: Although there were some individual differences, all 12 observers showed evidence for transfer of learning from the untrained eye to the fellow eye. This suggests that ‘monocular’ learning was due to learning to see through rivalry, and the locus of perceptual learning occurs at a stage higher than layer 4 of V1, after the input from the two eyes has come together.
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