Mechanics of cortical folding in a developing brain
Razavi Aghjeh, Mir Jalil
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Deciphering mysteries of the structure-function relationship in cortical folding has emerged as the cynosure of recent research on brain. Understanding the mechanism of convolution patterns can provide useful insight into the normal and pathological brain function. However, despite decades of speculation and endeavors the underlying mechanism of the brain folding process remains poorly understood. This dissertation studies mechanics of growth, instability and folding of a developing brain via theoretical analyses, computational modeling, and imaging verifications. Analytical interpretations of differential growth of the brain model provide preliminary insight into the critical growth ratio for instability and crease formation of the developing brain followed by computational modeling as a way to offer clues for brain’s post-buckling morphology. Especially, tissue geometry, growth ratio, and material properties of the cortex are explored as the most determinant parameters to control the morphogenesis of a growing brain model. Compressive residual stresses caused by the sufficient growth trigger instability and the brain forms highly convoluted patterns wherein its gyrification degree is specified with the cortex thickness. This dissertation also discusses the contribution of axon fibers on the formation of a special pattern as named 3-hinge on the brain. Morphological patterns of the developing brain predicted from the computational modeling are consistent with neuroimaging observations, thereby clarifying, in part, the reason of some classical malformation in a developing brain.