Abstract
Cortical folding, characterized by convex gyri and concave sulci, has an intrinsic relationship to the brain’s functional organization. Understanding the mechanism of the brain’s convoluted patterns can provide useful clues into normal and pathological brain function. In this paper, the cortical folding phenomenon is interpreted both analytically and computationally, and, in some cases, the findings are validated with experimental observations. The living human brain is modeled as a soft structure with a growing outer cortex and inner core to investigate its developmental mechanism. Analytical interpretations of differential growth of the brain model provide preliminary insight into critical growth ratios for instability and crease formation of the developing brain. Since the analytical approach cannot predict the evolution of cortical complex convolution after instability, non-linear finite element models are employed to study the crease formation and secondary morphological folds of the developing brain. Results demonstrate that the growth ratio of the cortex to core of the brain, the initial thickness, and material properties of both cortex and core have great impacts on the morphological patterns of the developing brain. Lastly, we discuss why cortical folding is highly correlated and consistent by presenting an intriguing gyri-sulci formation comparison.
Highlights
Brain development and related cerebral convolution have been fascinating research topics for more than a century[1,2,3,4,5]
Why is the primary cortical convolution organization across subjects within each species highly correlated and consistent rather than random, and what factors count for this consistency as regulators? What is the contribution of glial cells and axons in the convolution process, and how can their roles be considered in the mechanical models? The aim of this paper is to develop an integrated analytical and computational tool to better model the growth and instability of the developing brain, to investigate the criteria for instability and crease formation of the brain, and to link the instability to the geometrical and material properties of the brain
We have explored the morphological evolution and malformation mechanism of a developing brain in the fetal stage due to the biological growth from a mechanical viewpoint
Summary
Brain development and related cerebral convolution have been fascinating research topics for more than a century[1,2,3,4,5]. In the differential growth hypothesis, the outer layer of the brain grows at a faster rate than the inner layer, acting as the driving mechanism for cortical folding[15,16,17]. In most previous studies related to the elastic buckling models of the brain, the elastic modulus of the outer layer was higher than that of the core in order to produce buckling patterns which was not consistent with experimental observations[15,16]. A computational model of cortical convolution[21] suggested that without any additional assumption, the simple mechanical property of the cortex and differential growth are sufficient to produce cortical folding, which has been proven by other studies[13,17]. We will offer clues into the regulating mechanism of cortical folding by presenting an intriguing gyri-sulci formation comparison
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