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Jennifer M Yoon, Noah C Benson, Dylan Forenzo, Jonathan Winawer, Stephen A Engel, Kendrick N Kay; Heritability of V1/V2/V3 surface area in the HCP 7T Retinotopy Dataset. Journal of Vision 2019;19(10):41b. doi: https://doi.org/10.1167/19.10.41b.
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© ARVO (1962-2015); The Authors (2016-present)
The size of early visual areas differs greatly among individuals: how much of this variability is genetically determined? We analyzed 86 monozygotic (mz) and 58 dizygotic (dz) twins from the Human Connectome Project 7T Retinotopy Dataset (Benson et al., 2018, JOV). Based on the polar angle and eccentricity estimates in these data, we manually defined the extent of V1–V3 between 0.5 and 7 degrees eccentricity. We then quantified the surface area of these regions with respect to the mid-gray cortical surface. Individual differences in V1 surface area varied 3-fold and were highly heritable: r2 between twins was 46.5% and 36.5% for monozygotic and dizygotic pairs, respectively. Comparable levels of heritability were found for V2 (mz 50.9%, dz 25.4%) and V3 (mz 43.3%, dz 31.3%). Individual variability in V1/V2/V3 surface area might be predictable simply from overall brain size or the local anatomy (e.g., calcarine sulcus surface area). While total cortical surface area is highly heritable (mz r2=91.0%, dz 51.7%), it is not highly predictive of V1/V2/V3 surface area (r2=9.5%/16.2%/22.0%). We fit a multiple regression model including regressors for total cortical surface area, area of each subject’s calcarine sulcus, and V1 surface area measured in the paired twin. This model revealed that V1 surface area is best predicted by a combination of calcarine sulcus area and twin V1 surface area. These results quantify the heritability of functionally defined regions in a part of the brain that is known to be highly heritable (Patel et al, 2018). Yet only about half of the surface area variance in V1/V2/V3 is explained by genetics, suggesting substantial environmental influences on the topography of the earliest sensory maps in the human brain.
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