Heritability of Heschl’s Gyrus
Heschl's gyrus (HG), also known as the first transverse temporal gyrus, is located on the inferior surface of the lateral fissure. It includes the primary auditory cortex, which is the first cortical relay station of auditory information in the brain. Its anatomy is highly variable between individuals and hemispheres . Studies have shown a relationship between HG's structure and individual differences in language skill, learning and expertise, and dyslexia. Structural differences could be due to experience-dependent structural plasticity and/or to differences in pre-existing, innate factors . The aim of this research is to estimate the heritability of different HG structural measures: volume, thickness, surface area and shape. Knowledge about the heritability of HG anatomy could help to inform the origins of its relationship with musicianship or language aptitude.
Data from the Human Connectome Project was used for this study. The sample contained 426 MRI scans from 272 monozygotic and 154 dizygotic twins aged from 22 to 36 years. Two toolboxes (TASH and MCAI) [1,2] were applied to the data to extract HG structural measures. The classical twin design was used to estimate narrow-sense heritability (h2) . Variability in the HG structural measures was partitioned into 3 components: additive-genetic (A), common environmental (C) and residual variance (E) . Structural equation modelling was used to estimate A, C and E components.
Heritability estimates for bilateral HG surface area and volume and for right thickness were all low to moderate (ranging from h2=.02 to h2=.21) yet non-significant (all p>.16). Heritability estimated from left thickness, h2=0.51, was found to be significant (χ2(Δdf=1)=4.46, p=.03). Heritability of shape is yet to be estimated.
Interpretation of the results is a work in progress. However, power analysis showed that our study is underpowered to detect small heritability effects in surface area and volume, and marginally powered to detect them in thickness, which could help understand the origin of low heritability estimates.
 D. Marie et al., "Descriptive anatomy of Heschl’s gyri in 430 healthy volunteers, including 198 left-handers", Brain Struct Funct, vol. 220, no. 2, pp. 729–743, Mar. 2015. doi:10.1007/s00429-013-0680-x
 J. L. Dalboni da Rocha, O. Kepinska, P. Schneider, J. Benner, G. Degano, L. Schneider, and N. Golestani, “Multivariate concavity amplitude index (MCAI) for characterizing Heschl's gyrus shape,” NeuroImage, vol. 272, p. 120052, 2023.
 K. J. H. Verweij, M. A. Mosing, B. P. Zietsch and S. E. Medland, "Estimating Heritability from Twin Studies," in Statistical Human Genetics: Methods and Protocols, Totowa, NJ: Humana Press, 2012, pp. 151-170