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Carey Y. L. Huh, Eunice Yang, Michael Silver, Dennis Levi; Surround suppression in amblyopic central vision. Journal of Vision 2014;14(10):1415. doi: https://doi.org/10.1167/14.10.1415.
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© ARVO (1962-2015); The Authors (2016-present)
Amblyopia is typically characterized by reduced contrast sensitivity in the affected eye, particularly for high spatial frequencies that provide information about fine details in the visual scene. While this deficit suggests decreased gain of neural responses to high spatial frequencies, it is unclear whether lateral interactions among neurons are abnormal in amblyopia, and if so, whether the abnormality is specific to high spatial frequencies. To examine inhibitory lateral interactions, we measured surround suppression (SS) in adult amblyopes and age-matched normal observers. SS occurs when the detectability of a target is reduced by simultaneous presentation of a high-contrast stimulus surrounding the target. In normal observers, SS is much more pronounced in peripheral compared to central vision and may even be absent at the fovea. We found significant SS of a target grating in central vision of the amblyopic eye under conditions where little or no SS was found in either the non-amblyopic eye or in normal observers. For target gratings that are eight cycles wide, substantial SS was found in the amblyopic eye over a wide range of spatial frequencies (20 – 40% of the amblyopic eye's cutoff spatial frequency). In addition, SS was selective for surround gratings having the same orientation as the target, and significant SS was observed for centrally- and eccentrically-fixating amblyopes. Furthermore, we found that SS in amblyopic central vision was stronger for small target sizes, similar to normal peripheral vision. We are currently investigating the relationship between spatial frequency and SS and whether SS magnitude is proportional to the contrast sensitivity deficit of individual amblyopes. Our results demonstrate that amblyopic central vision displays substantial surround suppression that is absent or minimal at the fovea of normal observers. This finding supports the notion that amblyopia is characterized by abnormal interactions between neurons encoding neighboring visual field loci.
Meeting abstract presented at VSS 2014
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