Chicken and junglefowl cerebellar anatomy data

Domestication is the process by which wild organisms become adapted for
human use. Many phenotypic changes are associated with animal
domestication, including decreases in brain and brain region sizes. In
contrast to this pattern, the chicken has a larger cerebellum compared
with the wild red junglefowl, but what neuroanatomical changes are
responsible for this difference have yet to be investigated. Here, we
quantified cell layer volumes, neuron numbers and neuron sizes in the
cerebella of chickens and junglefowl. Chickens have larger, more folded
cerebella with more and larger granule cells than junglefowl, but neuron
numbers and cerebellar folding were proportional to cerebellum size.
However, chickens do have relatively larger granule cell layer volumes and
relatively larger granule cells than junglefowl. Thus, the chicken
cerebellum can be considered a scaled-up version of the junglefowl
cerebellum, but with enlarged granule cells. The combination of scaling
neuron number and disproportionate enlargement of cell bodies partially
supports a recent theory that domestication does not affect neuronal
density within brain regions. Whether the neuroanatomical changes we
observed are typical of domestication or not requires similar quantitative
analyses in other domesticated species and across multiple brain regions.