Proportional Cerebellum Size Predicts Fear Habituation in Chickens

Stingo-Hirmas, Diego; Cunha, Felipe; Cardoso, Rita France; Carra, Laura G.; Rönnegård, Lars; Wright, Dominic; Henriksen, Rie

doi:10.3389/fphys.2022.826178

Cited by 2 publications

(2 citation statements)

References 47 publications

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“…We used immunocytochemical detection of neuronal nuclear antigen NeuN, expressed in the nuclei of most neuronal types in the brain [30]. The samples were incubated overnight in a shaker and at 10 • C in mouse monoclonal antibody anti-NeuN 488 AlexaFluor conjugated (1:300 in phosphate-buffered saline; clone A60, Chemicon; MAB377X) [31,32]. A minimum of 500 nuclei were counted to estimate the proportion of neurons in the sample.…”

Section: Brain Dissection and Assessment Of Neuronsmentioning

confidence: 99%

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Selection for Reduced Fear of Humans Changes Brain and Cerebellum Size in Red Junglefowl in Line with Effects of Chicken Domestication

2023

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A central part of the domestication syndrome is a reduction in relative brain size. In chickens, it has previously been shown that domesticated birds have smaller relative brain mass, but larger relative mass of cerebellum, compared to their ancestors, the Red Junglefowl. It has been suggested that tameness may drive the domestication syndrome, so we examined the relationship between brain characteristics and tameness in 31 Red Junglefowl from lines divergently selected during ten generations for tameness. Our focus was on the whole brain, cerebellum, and the remainder of the brain. We used the isotropic fractionator technique to estimate the total number of cells in the cerebellum and differentiate between neurons and non-neuronal cells. We stained the cell nuclei with DAPI and performed cell counting using a fluorescence microscope. NeuN immunostaining was used to identify neurons. The absolute and relative masses of the brains and their regions were determined through weighing. Our analysis revealed that birds selected for low fear of humans (LF) had larger absolute brain mass, but smaller relative brain mass, compared to those selected for high fear of humans (HF). Sex had a significant impact only on the absolute size of the cerebellum, not its relative size. These findings support the notion that selection for increased tameness leads to an enlargement of the relative size of cerebellum in chickens consistent with comparisons of domesticated and ancestral chickens. Surprisingly, the HF birds had a higher density of neurons in the cerebellum compared to the LF line, despite having a smaller cerebellum overall. These findings highlight the intricate relationship between brain structure and behavior in the context of domestication.

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Section: Brain Dissection and Assessment Of Neuronsmentioning

confidence: 99%

“…A minimum of 500 nuclei were counted to estimate the proportion of neurons in the sample. By subtracting the number of neurons from the total cell count, we determined the number of non-neuronal cells [29,31].…”

Section: Brain Dissection and Assessment Of Neuronsmentioning

confidence: 99%

Selection for Reduced Fear of Humans Changes Brain and Cerebellum Size in Red Junglefowl in Line with Effects of Chicken Domestication

2023

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Neuronal and non-neuronal scaling across brain regions within an intercross of domestic and wild chickens

et al. 2022

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The allometric scaling of the brain size and neuron number across species has been extensively studied in recent years. With the exception of primates, parrots, and songbirds, larger brains have more neurons but relatively lower neuronal densities than smaller brains. Conversely, when considering within-population variability, it has been shown that mice with larger brains do not necessarily have more neurons but rather more neurons in the brain reflect higher neuronal density. To what extent this intraspecific allometric scaling pattern of the brain applies to individuals from other species remains to be explored. Here, we investigate the allometric relationships among the sizes of the body, brain, telencephalon, cerebellum, and optic tectum, and the numbers of neurons and non-neuronal cells of the telencephalon, cerebellum, and optic tectum across 66 individuals originated from an intercross between wild and domestic chickens. Our intercross of chickens generates a population with high variation in brain size, making it an excellent model to determine the allometric scaling of the brain within population. Our results show that larger chickens have larger brains with moderately more neurons and non-neuronal cells. Yet, absolute number of neurons and non-neuronal cells correlated strongly and positively with the density of neurons and non-neuronal cells, respectively. As previously shown in mice, this scaling pattern is in stark contrast with what has been found across different species. Our findings suggest that neuronal scaling rules across species are not a simple extension of the neuronal scaling rules that apply within a species, with important implications for the evolutionary developmental origins of brain diversity.

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Proportional Cerebellum Size Predicts Fear Habituation in Chickens

Cited by 2 publications

References 47 publications

Selection for Reduced Fear of Humans Changes Brain and Cerebellum Size in Red Junglefowl in Line with Effects of Chicken Domestication

Selection for Reduced Fear of Humans Changes Brain and Cerebellum Size in Red Junglefowl in Line with Effects of Chicken Domestication

Neuronal and non-neuronal scaling across brain regions within an intercross of domestic and wild chickens

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