Kocourek Martin, Zhang Yicheng, Sandberg Lucie, Stehlík Patrik, Polonyiová Alexandra, Olkowicz Seweryn, Straková Barbora, Pavelková Zuzana, Hájek Tomáš, Kušta Tomáš, Lučan Radek K, Kverková Kristina, Němec Pavel
Department of Zoology, Faculty of Science, Charles University, Prague, Czechia.
Department of Anatomy, Third Faculty of Medicine, Charles University, Prague, Czechia.
Brain Behav Evol. 2025 Mar 28:1-17. doi: 10.1159/000545417.
Songbirds, especially corvids, and parrots are remarkably intelligent. Their cognitive skills are on par with primates and their brains contain primate-like numbers of neurons concentrated in high densities in the telencephalon. Much less is known about cognition and neuron counts in more basal bird lineages. Here, we focus on brain cellular composition of galliform birds, which have small brains relative to body size and a proportionally small telencephalon and are often perceived as cognitively inferior to most other birds.
We use the isotropic fractionator to assess quantitatively the numbers and distributions of neurons and nonneuronal cells in 15 species of galliform birds and compare their cellular scaling rules with those of songbirds, parrots, marsupials, insectivores, rodents, and primates.
On average, the brains of galliforms contain about half the number of neurons found in parrot and songbird brains of the same mass. Moreover, in contrast to these birds, galliforms resemble mammals in having small telencephalic and dominant cerebellar neuronal fractions. Consequently, galliforms have much smaller absolute numbers of neurons in their forebrains than equivalently sized songbirds and parrots, which may limit their cognitive abilities. However, galliforms have similar neuronal densities and neuron counts in the brain and forebrain as equally sized non-primate mammals. Therefore, it is not surprising that cognitive abilities of galliforms are on par with non-primate mammals in many domains.
Comparisons performed in this study demonstrate that birds representing distantly related clades markedly differ in neuronal densities, neuron numbers, and the allocation of brain neurons to major brain divisions. In analogy with the concept of volumetric composition of the brain, known as the cerebrotype, we conclude that distantly related birds have distinct neuronal cerebrotypes.
鸣禽，尤其是鸦科鸟类和鹦鹉，具有非凡的智力。它们的认知能力与灵长类动物相当，其大脑中所含神经元数量与灵长类动物相似，且高密度地集中在端脑中。对于更为原始的鸟类谱系中的认知和神经元数量，我们了解得要少得多。在此，我们聚焦于鸡形目鸟类的脑细胞组成，这类鸟相对于体型而言大脑较小，端脑在比例上也较小，通常被认为在认知能力上不如大多数其他鸟类。
我们使用等密度分离法来定量评估15种鸡形目鸟类中神经元和非神经元细胞的数量及分布，并将它们的细胞缩放规则与鸣禽、鹦鹉、有袋动物、食虫动物、啮齿动物和灵长类动物的进行比较。
平均而言，相同质量的鸡形目鸟类大脑所含神经元数量约为鹦鹉和鸣禽大脑的一半。此外，与这些鸟类不同的是，鸡形目鸟类与哺乳动物相似，端脑神经元比例小，小脑神经元占主导。因此，与同等大小的鸣禽和鹦鹉相比，鸡形目鸟类前脑的神经元绝对数量要少得多，这可能会限制它们的认知能力。然而，鸡形目鸟类大脑和前脑中的神经元密度和神经元数量与同等大小的非灵长类哺乳动物相似。所以，鸡形目鸟类在许多方面的认知能力与非灵长类哺乳动物相当也就不足为奇了。
本研究中的比较表明，代表远缘进化枝的鸟类在神经元密度、神经元数量以及大脑神经元在主要脑区的分配上存在显著差异。类似于被称为脑型的大脑体积组成概念，我们得出结论，远缘相关的鸟类具有不同的神经元脑型。
