Sherwood Chet C, Broadfield Douglas C, Holloway Ralph L, Gannon Patrick J, Hof Patrick R
Department of Anthropology, Columbia University, New York, New York 10027, USA.
Anat Rec A Discov Mol Cell Evol Biol. 2003 Apr;271(2):276-85. doi: 10.1002/ar.a.10046.
The cortical circuits subserving neural processing of human language are localized to the inferior frontal operculum and the posterior perisylvian region. Functional language dominance has been related to anatomical asymmetry of Broca's area and the planum temporale. The evolutionary history of these asymmetric patterns, however, remains obscure. Although testing of hypotheses about the evolution of language areas requires comparison to homologous regions in the brains of our closest living relatives, the great apes, to date little is known about normal interindividual variation of these regions in this group. Here we focus on Brodmann's area 44 in African great apes (Pan troglodytes and Gorilla gorilla). This area corresponds to the pars opercularis of the inferior frontal gyrus (IFG), and has been shown to exhibit both gross and cytoarchitectural asymmetries in humans. We calculated frequencies of sulcal variations and mapped the distribution of cytoarchitectural area 44 to determine whether its boundaries occurred at consistent macrostructural landmarks. A considerable amount of variation was found in the distribution of the inferior frontal sulci among great ape brains. The inferior precentral sulcus in particular was often bifurcated, which made it impossible to determine the posterior boundary of the pars opercularis. In addition, the distribution of Brodmann's area 44 showed very little correspondence to surface anatomy. We conclude that gross morphologic patterns do not offer substantive landmarks for the measurement of Brodmann's area 44 in great apes. Whether or not Broca's area homologue of great apes exhibits humanlike asymmetry can only be resolved through further analyses of microstructural components.
人类语言神经处理所涉及的皮质回路定位于额下回盖部和颞叶周缘后区。功能性语言优势与布洛卡区和颞平面的解剖学不对称有关。然而，这些不对称模式的进化史仍不清楚。尽管关于语言区域进化的假设检验需要与我们现存的近亲——大猩猩大脑中的同源区域进行比较，但迄今为止，对于该群体中这些区域的正常个体间变异知之甚少。在这里，我们聚焦于非洲大猩猩（黑猩猩和大猩猩）的布罗德曼44区。该区域对应于额下回（IFG）的岛盖部，并且在人类中已显示出明显的大体和细胞结构不对称。我们计算了脑沟变异的频率，并绘制了细胞结构44区的分布图，以确定其边界是否出现在一致的宏观结构标志处。在大猩猩大脑中，发现额下回沟的分布存在相当大的变异。特别是中央前沟下部常常分叉，这使得无法确定岛盖部的后边界。此外，布罗德曼44区的分布与表面解剖结构的对应性非常小。我们得出结论，大体形态模式并不能为测量大猩猩的布罗德曼44区提供实质性标志。大猩猩的布洛卡区同源物是否表现出类似人类的不对称性，只能通过对微观结构成分的进一步分析来解决。
