Evolution of cytoarchitectural landscapes in the mammalian isocortex: Sirenians (Trichechus manatus) in comparison with other mammals.
Evolution of cytoarchitectural landscapes in the mammalian isocortex: Sirenians (Trichechus manatus) in comparison with other mammals.
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DOI：
10.1002/cne.23864
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发表时间：
2016-03-01
期刊：
影响因子：
--
通讯作者：
Finlay BL
中科院分区：
文献类型：
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作者：
Charvet CJ;Reep RL;Finlay BL
几种灵长类和啮齿类动物的同皮质显示出从其喙外侧到尾内侧边界每单位皮质表面积神经元数量的系统性增加。神经元数量和密度梯度的陡度与皮质体积呈正相关。神经发生的相对持续时间沿着相同的吻尾梯度预测的神经元数量和层状位置，这主要是由II-IV层神经元产生的这种变化的很大一部分。事实上，我们所有关于皮层神经元数量和神经发生的总体和分层变化的定量知识都来自啮齿动物和灵长类动物，然而，整个分类群体和许多中等大小的大脑尚未探索。因此，普遍存在于哺乳动物的皮质神经发生和皮质神经元数量增加，从皮质层II-IV的协变是不确定的。为了开始，以解决这个差距，我们研究了海牛的同皮质使用光学解剖方法在切片组织，也收集了部分数据，从国内猫的大脑发表的报告。海牛的同皮质神经元相对较少，每总体积，和较少的II-IV神经元比灵长类动物具有相同大小的大脑。从喙部到尾极的神经元数量梯度介于灵长类和啮齿类之间，就像那些只在上皮层观察到的物种一样。猫的同皮质（Felis alternaticus）也有类似的结构。进一步测试的起源，普遍存在的关键物种，这种组织特征的意义进行了讨论。用于神经元数量估计的海牛大脑冠状切片插图。在冠状面中，我们系统地采样了位点（即，每10个百分位数）沿同皮质的内侧到外侧轴沿着。最内侧的区域被指定为第10百分位数，最外侧的区域被指定为第90百分位数。箭头指向为神经元数量估计选择的近似位置。我们计算了一个单位的皮质表面积下的神经元数量（层II-VI神经元）。神经元数量的估计是通过皮层的深度进行的。计数帧被选择在等距的网站通过深度的皮质。在与皮质表面轴正交的位置取样。比例尺为1 mm。
The isocortex of several primates and rodents shows a systematic increase in the number of neurons per unit of cortical surface area from its rostro-lateral to caudo-medial border. The steepness of the gradient in neuronal number and density is positively correlated with cortical volume. The relative duration of neurogenesis along the same rostro-caudal gradient predicts a substantial fraction of this variation in neuron number and laminar position, which is produced principally from layers II–IV neurons. Virtually all of our quantitative knowledge about total and laminar variation in cortical neuron numbers and neurogenesis comes from rodents and primates, however, leaving whole taxonomic groups and many intermediate-sized brains unexplored. Thus, the ubiquity in mammals of the covariation of longer cortical neurogenesis and increased cortical neuron number deriving from cortical layers II–IV is undetermined. To begin to address this gap, we examined the isocortex of the manatee using the optical dissector method in sectioned tissue, and also assembled partial data from published reports of the domestic cat brain. The manatee isocortex has relatively fewer neurons per total volume, and fewer II–IV neurons than primates with equivalently sized brains. The gradient in number of neurons from the rostral to the caudal pole is intermediate between primates and rodents, and like those species observed only in the upper cortical layers. The cat isocortex (Felis domesticus) shows a similar structure. Key species for further tests of the origin, ubiquity, and significance of this organizational feature are discussed. Illustration of a coronally-sectioned manatee brain used for neuron number estimates. In coronal planes, we systematically sampled sites (i.e., every 10th percentile) along the medial to lateral axis of the isocortex. The most medially located region is designated as the 10th percentage and the most laterally selected region is designated as the 90th percentile. Arrow-heads point to the approximate sites selected for neuron number estimates. We counted neuron numbers (layers II–VI neurons) under a unit of cortical surface area. Neuron number estimates were made through the depth of the cortex. Counting frames were selected at equidistant sites through the depth of the cortex. Sites were sampled orthogonal to the axis of the cortical surface. Scale bar is 1mm.