Figure 3.

Analytical model of confined, layered medium subjected to growth-induced compression. Growing layer on an elastic foundation, left, and on a growing foundation, right. We model cortical folding using the classical fourth order Föppl-von-Kármán plate theory and adopt a sinusoidal ansatz for the deflection w, which generates a sinusoidal transverse force q. This provides analytical estimates for the critical cortical pressure P^crit and for the wavelength λ^crit parameterized in terms of the cortical thickness t_c, the cortical and subcortical Young’s moduli E_c and E_s, and the cortical and subcortical growth rates G_c and G_s.