Bishop Dorothy V M, Bates Timothy C
Department of Experimental Psychology, University of Oxford, Oxford, Oxon, OX2 6GG, UK.
Psychology Department, University of Edinburgh, Edinburgh, EH8 9JZ, UK.
Wellcome Open Res. 2020 Sep 16;4:161. doi: 10.12688/wellcomeopenres.15524.3. eCollection 2019.
Prior studies have estimated heritability of around 0.25 for the trait of handedness, with studies of structural brain asymmetry giving estimates in a similar or lower range. Little is known about heritability of functional language lateralization. This report describes heritability estimates using functional language laterality and handedness phenotypes in a twin sample previously reported by Wilson and Bishop (2018). The total sample consisted of 194 twin pairs (49% monozygotic) aged from 6 to 11 years. A language laterality index was obtained for 141 twin pairs, who completed a protocol where relative blood flow through left and right middle cerebral arteries was measured using functional transcranial Doppler ultrasound (fTCD) while the child described animation sequences. Handedness data was available from the Edinburgh Handedness Inventory (EHI) and Quantification of Hand Preference (QHP) for all 194 pairs. Heritability was assessed using conventional structural equation modeling, assuming no effect of shared environment (AE model). For the two handedness measures, heritability estimates (95% CI) were consistent with prior research: .25 (.03 - .34) and .18 (0 - .31) respectively for the EHI and QHP. For the language laterality index, however, the twin-cotwin correlations were close to zero for both MZ and DZ twins, and the heritability estimate was zero (0 - .15). A single study cannot rule out a genetic effect on language lateralisation. It is possible that the low twin-cotwin correlations were affected by noisy data: although the split-half reliability of the fTCD-based laterality index was high (0.85), we did not have information on test-retest reliability in children, which is likely to be lower. We cannot reject the hypothesis that there is low but nonzero heritability for this trait, but our data suggest that individual variation in language lateralisation is predominantly due to stochastic variation in neurodevelopment.
先前的研究估计利手性状的遗传率约为0.25，对大脑结构不对称性的研究给出的估计值在相似或更低的范围内。关于功能性语言偏侧化的遗传率知之甚少。本报告描述了在Wilson和Bishop（2018年）先前报告的双胞胎样本中，使用功能性语言偏侧化和利手表型的遗传率估计。总样本包括194对双胞胎（49%为同卵双胞胎），年龄在6至11岁之间。为141对双胞胎获得了语言偏侧化指数，他们完成了一个方案，即在孩子描述动画序列时，使用功能性经颅多普勒超声（fTCD）测量左右大脑中动脉的相对血流量。所有194对双胞胎都有来自爱丁堡利手量表（EHI）和手偏好量化（QHP）的利手数据。使用传统的结构方程模型评估遗传率，假设共享环境没有影响（AE模型）。对于两种利手测量方法，遗传率估计值（95%置信区间）与先前的研究一致：EHI和QHP分别为0.25（0.03 - 0.34）和0.18（0 - 0.31）。然而，对于语言偏侧化指数，同卵双胞胎和异卵双胞胎的双胞胎-同胞相关性都接近零，遗传率估计值为零（0 - 0.15）。一项研究不能排除基因对语言偏侧化的影响。低双胞胎-同胞相关性可能受到噪声数据的影响：尽管基于fTCD的偏侧化指数的分半信度很高（0.85），但我们没有关于儿童重测信度的信息，而重测信度可能更低。我们不能拒绝该性状存在低但非零遗传率的假设，但我们的数据表明语言偏侧化的个体差异主要是由于神经发育中的随机变异。
