Evolution of neocortical folding: A phylogenetic comparative analysis of MRI from 34 primate species

Abstract

We conducted a comparative analysis of primate cerebral size and neocortical folding using magnetic resonance imaging data from 65 individuals belonging to 34 different species. We measured several neocortical folding parameters and studied their evolution using phylogenetic comparative methods. Our results suggest that the most likely model for neuroanatomical evolution is one where differences appear randomly (the Brownian Motion model), however, alternative models cannot be completely ruled out. We present estimations of the ancestral primate phenotypes as well as estimations of the rates of phenotypic change. Based on the Brownian Motion model, the common ancestor of primates may have had a folded cerebrum similar to that of a small lemur such as the aye-aye. Finally, we observed a non-linear relationship between fold wavelength and fold depth with cerebral volume. In particular, gyrencephalic primate neocortices across different groups exhibited a strikingly stable fold wavelength of about 12 mm (± 20%), despite a 20-fold variation in cerebral volume. We discuss our results in the context of current theories of neocortical folding.

Cross-species cortical alignment identifies different types of neuroanatomical reorganization in the temporal lobe of higher primates

“…We dissociated cortical relocation of areas due to local expansion and modifications of white matter tract connectivity. Future work will expand this approach not only to different modalities, but also to a much wider range of species, which is now becoming increasing possible due to the availability of multi-species datasets (Heuer et al, 2018;Milham et al, 2018). This provides a crucial step towards the understanding of phylogenetic diversity across the primate brain.…”

Role of mechanical morphogenesis in the development and evolution of the neocortex

“…If the elasticity of the grey and the white matter were comparable, then λ~4.4t (Tallinen et al 2014). We have recently studied the variation of fold wavelength in 33 primate species (Heuer et al 2018). From vervet monkeys to humans, the wavelength was of 12 ± 2.4 (in close agreement with the mechanical model prediction) despite an 18-fold variation in brain volume.…”

Role of mechanical morphogenesis in the development and evolution of the neocortex

“…If the elasticity of the grey and the white matter were comparable, then λ~4.4t (Tallinen et al 2014). We have recently studied the variation of fold wavelength in 33 primate species (Heuer et al 2018).…”