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Cellular scaling rules for brains of gallinaceous birds
Zhang, Yicheng ; Němec, Pavel (advisor) ; Kratochvíl, Lukáš (referee)
Galliform birds (Galliformes) make up together with anseriform birds (Anseriformes) the clade Galloanserae, the sister group of Neoaves and the most basal clade of Neognathae. However, to date no quantitative data on cellular composition of their brains have been available. Here, I used the isotropic fractionator to determine numbers of neurons and non-neuronal cells in specific brain regions of 15 species of galliform birds. I find that cellular scaling rules for galliforms differ starkly from those for songbirds and parrots. When compared to these crown avian lineages, galliform birds feature lower degree of encephalization, a proportionally smaller telencephalon, small telencephalic and dominant cerebellar neuronal fractions, generally lower neuronal densities and larger glia/neuron ratios. Consequently, their brains and especially their forebrains harbor much smaller absolute numbers of neurons than those of equivalently sized songbird and parrots, the fact that undoubtedly constrains cognitive abilities of galliforms. However, this not to say that galliform birds are "bird brains" with low numbers of neurons and a limited ability to learn. Because they have high neuronal densities, their relatively small brains contain about equal numbers of neurons as brains of equivalently sized rodents and...
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Nervous system and cognitive abilities of gallinaceous birds
Zhang, Yicheng ; Němec, Pavel (advisor) ; Landová, Eva (referee)
2. Abstract Avian brain has traditionally been looked upon as a small, simple and almost entirely composed of basal ganglia and subserving exclusively instinctive behavior. In stark contrast to these obsolete notions, recent evidence demonstrates that, despite a lack of layered neocortex, extensive regions of the avian cerebrum are homologous to pallial components of the mammalian brain, conform to the same organizational principles and play similar roles in higher cognitive functions. Indeed, behavioural studies have shown that some birds have cognitive abilities that match or surpass those of mammals, most notably corvids and parrots rivalling the great apes in many cognitive domains. While these highly encephalized birds are often utilized as models in behavioural studies addressing avian cognitive capacities, less encephalized birds receive only scant attention. The gallinaceous birds (Galliformes), which together with the anseriform birds (Anseriformes) represent a sister group of Neoaves and the most basal clade of Neognathae, possess relatively small brains. Their cerebrotype is characterized by small forebrain, small nidopallium and large brain stem. Brain of gallinaceous birds is significantly lateralized. Brains of domesticated galliforms are significantly reduced in comparison to brain of their...
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