Role of Mechanical Factors in the Morphology of the Primate Cerebral Cortex
Figure 1
Mechanical Effects in Tissue Folding
(A) A simple mechanical model illustrates the deformation of tissue subjected to tangential force (F1) at an eccentricity (e) from the points of attachment, causing a moment, M. This mechanical deformation is represented by the general relation M = eF.
(B) The moment M causes the sheet to bend in a convex shape. The same principles apply to the second point of connection attachment, subjected to force F2, resulting in a convexity (gyrus) between connected regions, while a concavity (sulcus) forms between unconnected or weakly connected regions by default.
(C) Relative thickness (i.e., the ratio of the thickness of upper to lower cortical layers), changes when a 2-D section of cortical tissue, on the left, is bent into an annulus, on the right. Specifically, the relative thickness of the bent upper layers, d2, is smaller than that of the lower layers, d1. A mathematical derivation of these relations is given in Materials and Methods (“Bending a slab of layered neural tissue”).