Editorial: Functional columnar organization and long-range circuits in different cortical systems

The functional column is a classical concept which was introduced in the last century. This concept puts columns as organizing cortical units. It has largely influenced practical and theoretical research and also our understanding of neocortical processing. While it was initially attributed to early sensory cortical areas such as the primary visual cortex it can also be identified in higher sensory, multimodal or motor areas and their connections. Concomitant with the clustering of neurons of similar functional characteristics into periodic domains or columns extending through many cortical layers came the notion of a network of biased horizontal axons preferentially linking neurons with similar functional properties over short and long distances within a cortical area, and even between cortical areas, in a patchy manner. However, there is ample evidence for both selective and unselective long-range axons questioning the functional role of patchiness and the concept of the functional column in general.