Amunts Katrin, Schleicher Axel, Ditterich Annette, Zilles Karl
Institute of Medicine, Research Center Jülich, D-52425 Jülich, Germany.
J Comp Neurol. 2003 Oct 6;465(1):72-89. doi: 10.1002/cne.10829.
Functional imaging and clinical studies in children and adults have provided evidence of developmental changes in the hemispheric specialization for language. Whereas cytoarchitectonic asymmetry has been demonstrated in Broca's region of adults, the anatomical correlates of developmental changes in language dominance are largely unknown. In the present postmortem study of 34 human brains (ages ranging from 3.5 months to 85 years), the cytoarchitecture of areas 44 and 45 as the putative anatomical correlates of Broca's region, their developmental changes, and interhemispheric asymmetry were analyzed. Asymmetry as estimated by Euclidean distances between feature vectors of cytoarchitectonic profiles of left and right areas 44 and 45 was already found in 1-year-old infants. Asymmetry tended to increase with age, which was significant in area 45, but not in area 44. An adult-like, left-larger-than-right asymmetry in the volume fraction of cell bodies [gray level index (GLI)] was reached at approximately 5 years in area 45 and 11 years in area 44. These time points indicate a delayed development of the cytoarchitectonic asymmetry in Broca's region in comparison with that of the primary motor cortex. It may be hypothesized that the delayed maturation is the microstructural basis of the development of language abilities and the influence of language practice on cytoarchitecture during childhood. Interhemispheric asymmetry in the cytoarchitecture of areas 44 and 45 continues to change throughout life. We conclude that the cytoarchitectonic asymmetry of areas 44 and 45 is a result of microstructural plasticity that endures throughout almost the whole lifespan.
针对儿童和成人的功能成像及临床研究已为语言半球特化的发育变化提供了证据。虽然在成人的布洛卡区已证实存在细胞构筑不对称，但语言优势发育变化的解剖学关联在很大程度上尚不清楚。在本次对34例人脑（年龄范围从3.5个月至85岁）的尸检研究中，分析了作为布洛卡区假定解剖学关联的44区和45区的细胞构筑、它们的发育变化以及半球间不对称性。通过左右44区和45区细胞构筑轮廓特征向量之间的欧几里得距离估算的不对称性在1岁婴儿中就已发现。不对称性倾向于随年龄增加，这在45区显著，但在44区不显著。在45区约5岁时以及在44区约11岁时，细胞体体积分数[灰度指数（GLI）]达到了类似成人的左大于右的不对称性。这些时间点表明布洛卡区细胞构筑不对称性的发育相较于初级运动皮层有所延迟。可以推测，延迟成熟是语言能力发展以及童年期语言练习对细胞构筑影响的微观结构基础。44区和45区细胞构筑的半球间不对称性在整个生命过程中持续变化。我们得出结论，44区和45区的细胞构筑不对称性是微观结构可塑性的结果，这种可塑性几乎在整个生命周期中都存在。
