Shepherd Gordon M, Rowe Timothy B
Department of Neuroscience, Yale University School of Medicine, New Haven, CT, United States.
Jackson School of Geosciences, University of Texas at Austin, Austin, TX, United States.
Front Neuroanat. 2017 Nov 7;11:100. doi: 10.3389/fnana.2017.00100. eCollection 2017.
The neocortex is characterized by lamination of its neuron cell bodies in six layers, but there are few clues as to how this comes about and what is its function. Recent studies provide evidence that evolution from simple three-layer cortex may give insight into this problem. Three-layer cortex arose in the olfactory, hippocampal and dorsal cortex of the early amniote forebrain based on a cortical module of excitatory and inhibitory inputs to an intratelencephalic (IT) type of pyramidal neuron with feedback excitation and inhibition and related interneurons. We summarize recent evidence suggesting the hypothesis that the developmental program of three-layer olfactory cortex was co-opted to form six-layer mammalian neocortex, elaborating IT cortical units in layers 2-6 while adding layer 4 stellate cells, layer 5B pyramidal tract (PT) cells and layer 6 corticothalamic (CT) cells.
新皮层的特征在于其神经元细胞体分层为六层，但对于这种分层是如何形成的以及其功能是什么，几乎没有线索。最近的研究提供了证据表明，从简单的三层皮层进化而来可能有助于深入了解这个问题。基于对具有反馈兴奋和抑制作用的脑内（IT）型锥体神经元以及相关中间神经元的兴奋性和抑制性输入的皮质模块，三层皮层出现在早期羊膜动物前脑的嗅觉、海马和背侧皮层中。我们总结了最近的证据，提出了这样一个假说：三层嗅觉皮层的发育程序被采用来形成六层哺乳动物新皮层，在第2 - 6层中细化IT皮质单元，同时增加第4层星状细胞、第5B层锥体束（PT）细胞和第6层皮质丘脑（CT）细胞。
