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Jun-Yun Zhang, Lin-Juan Cong, Stanley Klein, Dennis Levi, Cong Yu; Decoupling orientation specificity from perceptual learning in amblyopic vision. Journal of Vision 2012;12(9):286. doi: https://doi.org/10.1167/12.9.286.
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© ARVO (1962-2015); The Authors (2016-present)
Perceptual learning (PL) has been shown to improve many visual functions in amblyopes, but this learning is often specific to the trained orientation, possibly implying neural plasticity in the amblyopic early visual cortex. However, orientation specificity in normal vision can be decoupled from PL with a training-plus-exposure (TPE) technique (Zhang et al., JNS2010). Specifically, PL transfers to an untrained orthogonal orientation when training is accompanied by additional exposure of the transfer orientation when an irrelevant task is performed. The transfer suggests PL occurs in higher brain areas. Here we used the TPE technique in adults with amblyopia to investigate whether PL reflects V1 plasticity or improved high-level decision making in the amblyopic brain.
Eighteen adult amblyopes participated. Similar to normal vision we found: (1) PL of contrast discrimination in the fovea of amblyopic eyes (AEs) did not transfer to an orthogonal orientation. However, AEs were then exposed to the orthogonal transfer orientation through irrelevant orientation discrimination training at the transfer orientation, which enabled contrast learning to transfer to the orthogonal orientation. (2) We found similar transfer in the AEs after the non-amblyopic eyes (NAEs) were exposed. (3) Orientation specificity in Vernier and orientation learning was also eliminated by exposure of the transfer orientation in AEs or NAEs through irrelevant orientation or contrast training. (4) Surprisingly, orientation specificity in NAE Vernier learning was eliminated after AEs were exposed to the orthogonal transfer orientation, indicating that the AE can teach the NAE.
TPE enabled learning transfer across orientations suggests that perceptual learning in amblyopic vision may not reflect plasticity in local circuits in the amblyopic early visual cortex. Rather it may result from improved readout of noisy stimulus inputs at the decision stage that, at least in part, compensates for the functional deficits in the amblyopic visual system.
Meeting abstract presented at VSS 2012
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