Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden.
Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden.
Curr Biol. 2017 Nov 6;27(21):3264-3277.e5. doi: 10.1016/j.cub.2017.09.034. Epub 2017 Oct 19.
The basic architecture of the mammalian neocortex is remarkably similar across species. Pallial structures in the reptilian brain are considered amniote precursors of mammalian neocortex, whereas pallia of anamniotes ("lower" vertebrates) have been deemed largely insignificant with respect to homology. Here, we examine the cytoarchitecture of the lateral pallium in the lamprey, the phylogenetically oldest group of extant vertebrates. We reveal a three-layered structure with similar excitatory cell types as in the mammalian cortex and GABAergic interneurons. The ventral parts are sensory areas receiving monosynaptic thalamic input that can be activated from the optic nerve, whereas the dorsal parts contain motor areas with efferent projections to the brainstem, receiving oligosynaptic thalamic input. Both regions receive monosynaptic olfactory input. This three-layered "primordial" lamprey lateral pallium has evolved most features of the three-layered reptilian cortices and is thereby a precursor of the six-layered "neo" cortex with a long-standing evolutionary precedent (some 500 million years ago).
哺乳动物新皮质的基本结构在物种间非常相似。爬行动物大脑中的皮层结构被认为是哺乳动物新皮质的羊膜祖先，而无羊膜动物（“低级”脊椎动物）的皮层则被认为在同源性方面意义不大。在这里，我们研究了现存最古老的脊椎动物——七鳃鳗的外侧脑皮层的细胞结构。我们揭示了一个具有三层结构的大脑区域，其中包含与哺乳动物皮层相似的兴奋性细胞类型和 GABA 能中间神经元。腹侧部分是接收单突触丘脑输入的感觉区域，可以通过视神经激活，而背侧部分包含具有向脑干传出投射的运动区域，接收寡突触丘脑输入。这两个区域都接收单突触嗅觉输入。这个三层结构的“原始”七鳃鳗外侧脑皮层已经进化出了三层结构的爬行动物皮层的大多数特征，因此是具有悠久进化历史（约 5 亿年前）的六层结构“新”皮层的前身。
