Department of Anthropology, University College London, London WC1H 0BW, United Kingdom.
Evolution. 2012 Aug;66(8):2551-63. doi: 10.1111/j.1558-5646.2012.01601.x. Epub 2012 Apr 12.
A major focus of comparative neuroanatomy has been on whether the mammalian brain evolves in a concerted or a mosaic fashion. Workers have examined variation in the volume of different brain regions across taxa to test the degree to which selection is constrained by the timing of events in neural development. Whether a conserved neurogenetic program in the mammalian brain constrains the distribution of different cell types, however, has not yet been investigated. Here we tested for evidence of evolutionary constraints on the densities of different cell types in the primary visual cortex (V1) and the hippocampus in 37 primate and 21 carnivore species. Cellular densities in V1 and the hippocampus scale isometrically with respect to one another in carnivores, as predicted by the concerted evolution hypothesis. In primates, however, cellular distributions in the hippocampus and primary visual cortex show no correlations, which supports the hypothesis of mosaic brain evolution. We therefore provide evidence for the presence of constraints controlling the adult densities of different cell types in disparate regions of the mammalian brain, but also for specializations along the primate lineage. We propose that adaptations to modularity at the cellular level may carry a deep phylogenetic signal.
比较神经解剖学的一个主要焦点是哺乳动物的大脑是协同进化还是镶嵌进化。研究人员检查了不同分类群中不同脑区体积的变化，以检验选择在多大程度上受到神经发育事件时间的限制。然而，哺乳动物大脑中是否存在保守的神经发生程序来限制不同细胞类型的分布，这一点尚未得到研究。在这里，我们在 37 种灵长类动物和 21 种食肉动物中测试了初级视觉皮层 (V1) 和海马体中不同细胞类型密度的进化约束的证据。正如协同进化假说所预测的那样，在食肉动物中，V1 和海马体的细胞密度与彼此之间是等距的。然而，在灵长类动物中，海马体和初级视觉皮层的细胞分布没有相关性，这支持了大脑镶嵌进化的假说。因此，我们提供了证据证明存在控制哺乳动物大脑不同区域不同细胞类型成年密度的约束，但也证明了沿着灵长类动物谱系的专门化。我们提出，细胞水平上对模块性的适应可能具有深刻的系统发育信号。
