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Surface Ratio
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The degree of folding of a brain is traditionally estimated by comparing the area of the cortical surface with the area of its external surface, or the ratio between the pial contour and the outer contour in successive coronal sections. The Surface Ratio extends these ideas to obtain a local estimate of the degree of cortical folding. For every point x on the cortical surface we compute the cortical area contained in a small sphere of fixed radius r centred at x. If the brain were lissencephalic, the area inside the sphere would be approximately that of the sphere's disc. We estimated the local degree of folding through the surface ratio:

Toro R et al (2008) Brain size and folding of the human brain. Cerebral Cortex

last update 6 january 2008, roberto toro
brain & body centre | university of nottingham | nottingham, UK