近日，国际著名学术期刊《美国国家科学院院刊》杂志在线发表了捷克布拉格查理大学Seweryn Olkowicz研究员的一篇研究论文，研究显示从前脑神经元的全部数量来说，一些鸟类要比人们曾经认为的聪明很多。

本研究发现和拥有类似尺寸脑袋的哺乳动物相比，28个鸟类物种在大脑皮质端脑中拥有更多神经元，尤其是鹦鹉和鸣禽表现更佳。鹦鹉(如图中的灰鹦鹉)的神经元数量为2.27亿～31.4亿个，而鸣禽——包括以聪明著称的乌鸦——的神经元数量为13.6亿～21.7亿个。这约是大脑质量相同的灵长类动物所拥有神经元数量的两倍，并且是大脑质量相同的啮齿类动物所拥有神经元数量的4倍。

研究人员解剖了这些鸟类的大脑，然后将其溶解在清洗剂溶液中，以确保细胞悬浮在被美国田纳西州范德堡大学神经学家Suzana Herculano-Houzel称为“脑汤”的溶液中。这使他们得以标记、计数并且估测某个特定大脑区域存在多少神经元。研究人员聚焦的区域能让一些鸟类磨练诸如工具使用等技能、为未来做规划、学习鸟鸣，以及模仿人类讲话。

一项令人吃惊的发现是，神经元比预期的小很多，而细胞之间的连接更短、更紧凑。该团队下一步将分析这些神经元是否一开始就很小，还是后来萎缩了，以便使鸟类为了飞行而保持足够的轻便。不过，至少有一件事情是明确的：是时候为你没有那么聪明的朋友寻找一种新的羞辱了。

原文摘要：Some birds achieve primate-like levels of cognition, even though their brains tend to be much smaller in absolute size. This poses a fundamental problem in comparative and computational neuroscience, because small brains are expected to have a lower information-processing capacity. Using the isotropic fractionator to determine numbers of neurons in specific brain regions, here we show that the brains of parrots and songbirds contain on average twice as many neurons as primate brains of the same mass, indicating that avian brains have higher neuron packing densities than mammalian brains. Additionally, corvids and parrots have much higher proportions of brain neurons located in the pallial telencephalon compared with primates or other mammals and birds. Thus, large-brained parrots and corvids have forebrain neuron counts equal to or greater than primates with much larger brains. We suggest that the large numbers of neurons concentrated in high densities in the telencephalon substantially contribute to the neural basis of avian intelligence.