The pattern and complexity of cerebellar folding varies across vertebrates. However, little is known about how the tissue-level mechanics are adjusted to create species-specific folding patterns. Here, we utilize a variety of species with differences in cerebellar folding amount to investigate two tissue-level mechanics known to affect folding—differential expansion and outer layer thickness. We found that the level of differential expansion between the outer and inner layers of the cerebellum broadly correlates with folding amount and that the thickness of the outer layer is important as thicker outer layers require more differential expansion to fold. Additionally, we find that both the proliferation rate and division angle of cells in the outer layer are adjusting these two mechanics. This work will shed light on the conservation of the tissue mechanics that regulate brain folding and how these mechanics may be modulated to set the diverse folded morphologies observed across species.

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