Figures and data
The diversity of the cortical morphologies and developmental processes across species.
(a) Phylogenetic relationship of species. Adapted from [6, 7]. Typical real brain surfaces of ferret and primates are presented. Color represents mean curvature. Scale bars: 1 cm (estimated from [23]). (b) Stained sections of mature brain tissue from ferret, rhesus macaque, and human. Scale bar: 10 mm. Adapted from [24]. (c-e) 3D reconstruction of cortical surfaces of ferret, macaque, and human brains from fetal to adult. (c) Ferret: postnatal day 4, 10, 17 and adult maturation [25]. Scale bar: 1cm; (d) Macaque: gestation day 85, 110, 135 [26], and adult maturation [27]. Scale bar: 1cm; (e) Human: gestation day 175 (week 25), 210 (week 30), 231 (week 33), 273 (week 39), and adult maturation [25]. Scale bar: 5cm.
Physical gel model that recapitulates the growth-driven morphogenesis mechanism across phylogeny and developmental stages.
(a) A time-lapse of the physical gel brain mimicking macaque brain development starting from G110. (b) Left views of three physical gels mimicking macaque post gestation day 85, day 110, and day 135 before and after hexane swelling. Scale bar: 1 cm. (c) Comparison of fetal/newborn brain scans and the reconstructed surfaces of swollen physical gels for various species. Scale bars: 1 cm.
Simulations of growing brains of
(a) ferret, (b) rhesus macaque, and (c) human. Starting from smooth fetal/newborn brains, simulations show different gyrification patterns across species. The brains are modeled as soft elastic solids with tangential growth in the gray matter (see Simulations of growing brains for details). Initial 3D geometries are taken from the reconstruction of MRI (see Methods, 3D model reconstruction). Mechanical parameters of growth ratio and cortical thickness are provided in Table 2. Color from dark to light blue represents shape index (as defined in Eq. (2)) from −1 to 1.
Comparison among real (1), simulated (2), and gel brains (3) of ferret, rhesus macaque, and human via morphometric analysis.
(a) 3D cortical surfaces of in vivo, in silico, and in vitro models. Left brain surfaces are provided here. The symmetry of the left and right halves of brain surfaces is discussed in Fig. S3 and S4, Movie S2–S4. (b) The quasi-conformal disk mapping with landmark matching of cortical surfaces on disk (see Sec Morphometric analysis for details). Blue or red curves represent corresponding landmarks. Color represents shape index (SI, as defined in Eq. (2)). Similarity indices of each simulated and gel brain surfaces are presented in Table 1. (c) Histogram of shape index of ferret, macaque, and human. Black, red, and blue dots represent the probability of shape index of real, gel, and simulated surfaces, respectively.
Similarity index evaluated by comparing the shape index of simulated brains (S), swollen gel brain simulacrums (G) and real brain surfaces (R), calculated with vector p-norm p = 2, as described in Eq. (4).
