Annett M
Department of Psychology, University of Leicester, UK.
Neurosci Biobehav Rev. 1996 Winter;20(4):631-6. doi: 10.1016/0149-7634(95)00076-3.
The right shift theory of handedness and cerebral specialization suggests that there is an underlying substrate of random lateral asymmetries in all higher animals and a specific factor in humans which increases the probability of left hemisphere advantage. The specific factor displaces the random distribution along a continuum of asymmetry in favour of the left hemisphere and the right hand. The distribution of handedness in families can be explained if the shift to dextrality depends on a single gene, rs +, when the frequency of the gene is estimated from the proportion of dysphasics with unilateral lesions of the left versus the right hemisphere. The gentoype proportions suggested a genetic balanced polymorphism with heterozygote advantage for laterality and ability. Application of the model to developmental dyslexia led to the hypothesis that both homozygotes (rs -- and rs ++ genotypes) are at risk for reading. The critical question was whether the type of cognitive problem differs as expected, speech based processing for the rs -- and non-speech based for the rs ++. The former should include more left and mixed handers, while the latter should be more strongly dextral than controls. Evidence for this double dissociation between type of cognitive disability and type of handedness has been found in poor readers and in other samples.
利手与大脑特化的右移理论表明，所有高等动物都存在潜在的随机侧不对称基质，而人类存在一个特定因素，它增加了左半球优势的概率。该特定因素使随机分布沿着不对称连续统发生位移，偏向于左半球和右手。如果转向右利手取决于单个基因rs +，那么当从左半球与右半球单侧损伤的言语障碍患者比例估计该基因的频率时，家族中利手的分布就能得到解释。基因型比例表明存在一种遗传平衡多态性，杂合子在利手性和能力方面具有优势。将该模型应用于发育性阅读障碍，得出这样的假设：两种纯合子（rs -- 和rs ++ 基因型）都有阅读风险。关键问题在于认知问题的类型是否如预期那样不同，即rs -- 型基于言语处理，rs ++ 型基于非言语处理。前者应该包括更多左利手和混合利手，而后者应该比对照组更倾向于右利手。在阅读能力差的人群和其他样本中已经发现了认知障碍类型与利手类型之间这种双重分离的证据。
