近日，美国加利福尼亚州大学圣地亚哥医学院的科学家最新研究显示，鸟类掌控听力输入的大脑区域与人类等哺乳动物非常接近，暗示着人类与鸟类大脑之间的相似性超出之前的观点，同时，这种相似性可能起源自3亿年前哺乳动物和鸟类的共同祖先。

一个世纪以来，神经学科学家都认为人类和其它哺乳动物的大脑与鸟类等动物的大脑存在着差异。主要表面在大脑新皮层(neocortex)的物理结构，该区域是大脑负责掌控复杂的认知能力。来自加利福尼亚州大学圣地亚哥医学院的哈维－卡尔顿(Harvey J. Karten)教授和研究同事颠覆了这一观点，在最新的研究中，他们使用高敏感绘图仪等现代复杂的图像技术，绘制出鸟的大脑区域，发现鸟大脑与哺乳掌控听力的皮层非常相似。这项发现证实鸟大脑皮层区域也包含着通过不同狭窄、辐射纵向细胞类型连接的薄细胞层。

该研究显示大脑新皮层细胞的纤薄和柱向柱状结构并不是哺乳动物所独有的，或许进化于更远古的脊椎动物祖先。

卡尔顿称，这一最新研究为神经学专家提出了一个严峻的难题——哺乳动物大脑新皮层的进化起源，这种复杂的新皮层最初的进化起源在哪里？他猜测可能源自3亿年前哺乳动物和鸟类的共同祖先。

原文出处：

PNAS April 1, 1997 vol. 94 no. 7 2800-2804

Evolutionary developmental biology meets the brain: The origins of mammalian?cortex
Harvey J. Karten

Genes Are Highly Conserved. But Where Does Novelty Arise?
“The central problem for evolutionary biologists interested in development has been how morphology is transformed in evolution. In 1922, Walter Garstang made the very basic observation that because the morphology of animals arises anew in each generation, evolution of new animal forms has to be viewed as a problem in the evolution of development.” R. A. Raff (1)

For most of the past 100 years, the evolutionary origins of the mammalian cortex and the development of the mammalian cortex have been studied as if the two issues were completely unrelated to each other. The paper by Kuan et al. (2) in the current issue of the Proceedings raises a number of important issues for the fields of evolution and cortical development and attempts to bridge this gap. This paper also comes at a time in which molecular genetics has forced us to deal with the “meaning” of major gene families found across all vertebrates and invertebrates.

The Telencephalon of Nonmammals and the Phylogeny of Neocortex
Where Did Neocortex Come From?Until the latter part of the twentieth century, the prevailing view of the origins of the mammalian neocortex consisted of a series of loosely conceived proposals, with the common theme that the mammalian neocortex arises within the thin pallial mantle region as found in reptiles. This supposed that all the specific neurons of the cortex, including those in receipt of thalamic input, interneurons, and output neurons, were newly evolved in mammals and were constitutively organized as a laminar structure. This hypothesis also implied that the specific sensory nuclei of the thalamus that provide the inputs to the cortex were also uniquely mammalian.