Cerebral Cortex - Cortical Thickness

Cortical Thickness

For mammals, species with larger brains (in absolute terms, not just in relation to body size) tend to have thicker cortices. The range, however, is not very great — only a factor of 7 between the thickest and thinnest cortices. The smallest mammals, such as shrews, have a neocortical thickness of about 0.5 mm; the ones with the largest brains, such as humans and fin whales, have thicknesses of 2.3—2.8 mm. There is an approximately logarithmic relationship between brain weight and cortical thickness; dolphins, however, have considerably thinner cortices than the overall relationship would predict.

With magnetic resonance brain scanners, it is possible to get a measure for the thickness of the human cerebral cortex and relate it to other measures. The thickness of different cortical areas varies. In general, sensory cortex is thinner and motor cortex is thicker. One study has found some positive association between the cortical thickness and intelligence. Another study has found that the somatosensory cortex is thicker in migraine sufferers.