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Anthony M. Norcia, Sean I. Chen, Arvind Chandna; Experience Dependent Plasticity of human Form and Motion Mechanisms in Anisometropic Amblyopia. Journal of Vision 2010;10(7):19. doi: 10.1167/10.7.19.
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Deprivation of visual input during developmental critical periods can have profound effects on the structure of visual cortex and on functional vision (Hubel and Wiesel 1963). Converging evidence from studies in human and animal models of amblyopia suggests that visual deprivation can have differential effects on different cortical pathways, consistent with the presence of multiple critical periods within the visual system as a whole (Harwerth, Smith et al. 1986). Anisometropia (unequal refractive error between the two eyes) is a common clinical condition in humans that can lead to very deep amblyopia if not treated. We studied the effects of visual deprivation secondary to anisometropia in a group of children before and after treatment for amblyopia. We recorded Visual Evoked Potentials (VEPs) evoked by vernier offsets of different sizes. This VEP paradigm (Norcia, Wesemann et al. 1999) elicits two qualitatively dissimilar response components, one associated with relative alignment or spatial position cues (form) and the other with transients due to motion or contrast change (motion). Prior to treatment, the non-deprived eye shows supernormal form responses and normal motion responses. The amblyopic eye shows markedly reduced form responses and moderately reduced motion responses. Treatment via patching and glasses partially normalized the form responses in both eyes but had less of an effect on motion responses. The results indicate that form mechanisms are differentially susceptible to deprivation of high spatial frequency inputs during a developmental critical period.
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