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Emily Blumenthal, Rain Bosworth, Karen Dobkins; Genetic and Environmental Contributions to Chromatic and Luminance Contrast Sensitivity in Infant Twins. Journal of Vision 2012;12(9):474. doi: 10.1167/12.9.474.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction: The purpose of the present study was to determine the relative contribution of shared genetic and environmental factors to infants’ contrast sensitivity (CS) for Chromatic and Luminance patterns, which are mediated by the parvocellular and magnocellular pathways, respectively. If CS is governed by genetics, monozygotic (Mz) twin pairs’ sensitivity should be more highly correlated than dizygotic (Dz) twin pairs’ performance, because Mz twins share, on average, twice as many genes than Dz twins share (100% vs. 50%). If genetics are not influential, the correlations between Mz and Dz twins should be equivalent. Methods: Thirteen Mz and 45 Dz twin pairs were tested (M age=4.6 months, SD=1.4). Zygosity was assessed by questionnaire and cheek swab samples. Using forced-choice preferential looking, contrast sensitivities were obtained for Chromatic (red/green isoluminant) and Luminance (dark/light) moving sinusoidal gratings (0.27 cpd; 4.2 Hz; cone contrasts between 2-46% randomized across ~160 trials). Structural equation modeling (SEM, Neale et al., 2003) was applied to determine which factors explain the variance in twin pairs’ CS: additive genes (A), common/shared environment (C), and unique environment (E). Results: Logged CSs were entered into the SEM model with infants’ age as a covariate. The best model fit for Chromatic CS included the genetic and unshared environment factors (AE model; RMSEA=0.08). Genetics accounted for 37% of the variance in this model. The best model fit for Luminance CS included shared and unshared environment factors (CE model; RMSEA=0.08). In this model, shared environment explained 52% of the variance in Luminance CS. Conclusion: These preliminary results suggest that both genetic and shared environmental factors influence early contrast sensitivity, and effects differ for the parvocellular (Chromatic CS) than magnocellular (Luminance CS) pathways.
Meeting abstract presented at VSS 2012
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