ABSTRACT
The cortex is subdivided into anatomically recognizable areas. This phenomenon, though described in detail nearly a century ago, is still difficult to grasp precisely. The local differences in structure are subtle enough to have evoked debates which still continue about the exact definition of a cortical area, the number of areas, the exact location of their borders and the comparability of areas between species. It depends on the context whether one considers the cortex as a more or less homogeneous structure, or rather emphasizes its heterogeneity. In view of the very different tasks in which the cortex is involved, such as sensory processing of different modalities, learning, long-term planning, decision taking, movement or human speech, one may be impressed by the relative homogeneity of the overall structure of the cortex, both within and between species. If, on the other hand, one compares the cerebral cortex to the cerebellar cortex, which shows no signs of local differences in architectonics, the heterogeneity of the structure of the cerebral cortex is striking.
