Cortical column

This article uses direct referencing.

Cortical columns are groups of cells in the cerebral cortex that are ontogenetic clones of the same precursor neuron. They are arranged radially according to the number of cell cycles of the precursor: while the older postmitotic neurons remain in the deep layers, the younger ones migrate to the superficial layers of the cortex, following the marginal zone. The term cortical column is also often used in non-ontogenetic contexts (for review on functional aspects, see Horton & Adams, 2005), thereby broadening its meaning with respect to the more precise ontogenetic column.

Significance

Since the 1970s, cortical columns have been widely regarded as the basic computational unit of the neocortex (cf. Mountcastle 1978), with their quantity being the main determinant of the intelligence of a specific mammal and the general intelligence of its species. Following an influential paper by Rockel et al. (1980), cortical columns are generally assumed to be uniformly organized across brain areas within a species (with the exception of the primate visual cortex) and across mammalian species. They are usually described in terms of macrocolumns which consist of about a thousand minicolumns that are found all throughout the neocortex, with a diameter of roughly 0.5mm which is also about the distance between the center of two separate columns.

Controversy

The view of the uniformity of the mammalian neocortex has been challenged repeatedly (cf. Haug 1987, Herculano-Houzel et al., 2008 and Rakic 2008), which gave rise to the notion of ontogenetic columns (Rakic 1988).