Cortical thickness

In neuroanatomy, cortical thickness is a brain morphometric measure used to describe the combined thickness of the layers of the cerebral cortex in mammalian brains, either in local terms or as a global average for the entire brain. Given that cortical thickness roughly correlates with the number of neurons within an ontogenetic column, it is often taken as indicative of the cognitive abilities of an individual, albeit the latter are known to have multiple determinants. In other anatomical contexts, the term cortical thickness is also used on occasion to refer to the thickness of the renal cortex or of cortical bone.

In the living brain, cortical thickness is commonly determined on the basis of the grey matter set in segmented neuroimaging data, usually from the local or average distance between the white matter surface and the pial surface. It changes only minimally with brain size, both within and across species. Its variation across the human brain follows small-world principles, and while overall sex differences in terms of cortical thickness are small in humans, women have slightly higher values in temporoparietal regions than men. Typical values in adult humans are between 1.5 and 3 mm, and during aging, a decrease (also known as cortical thinning) on the order of about 10 μm per year can be observed . Deviations from these patterns can be used as diagnostic indicators for brain disorders: While Alzheimer's disease, even very early on, is characterized by pronounced cortical thinning, Williams syndrome patients exhibit an increase in cortical thickness of about 5-10% in some regions , and lissencephalic patients show drastic thickening, up to several centimetres in occipital regions.