Ontogeny and phylogeny in brain folding

In adults, cortical thickness varies locally from 1 to nearly 5mm.  How do those differences emerge throughout development?  How similar are these patterns to non-human primates and other mammals? 

We have shown that cortical thickness in gyri and sulci diverge during the early years of postnatal development (Holland et al. 2020), and we are currently investigating these changes during in utero developmen.  To complement this research, we are also studying the patterns of cortical folding and thickness across mammalian phylogeny, starting with primates.  In our preliminary analysis of 12 primate species (Demirci et al., submitted), we found similar qualitative patterns of thickness - where the most sulcal regions are the thinnest, and the most gyral regions are the thickest.  Quantitatively, our results matched our predictions from numerical simulations (Holland et al. 2018) - the difference between the thickest and thinnest regions increased as brain size and foldedness increased.  In the future, we plan to study many more species, including both additional primates and other mammals.

Images of brains - on the top, primate evolution is represented by a small, smooth night monkey brain, a larger and more folded chimpanzee brain, and the very large human brain.  On the bottom, human development is shown similarly, from a small smooth brain at 22 weeks of gestation, to an intermediate stage at 35 weeks, and the same large and highly folded adult human brain.

Holland MA, Budday S, Goriely A, Kuhl E (2018) "Symmetry Breaking in Wrinkling Patterns: Gyri Are Universally Thicker than Sulci." Physical Review Letters

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Holland MA, Budday S, Li G, Shen D, Goriely A, Kuhl E (2020) "Folding drives cortical thickness variations." European Physical Journal Special Topics

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Primate

Demirci N, Hoffman ME, Holland MA (submitted) "Systematic cortical thickness patterns in primates suggest a universal physical law of folding."  

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