Segregation of the inputs from the right and left eyes into columns that form alternating bands in the primary visual cortex. Today a ‘column’ is understood to be cells in any vertical cluster that share the same tuning for any particular for any given receptive field attribute. More broadly speaking, a ‘column’ refers to periodic termination of axons with and between cortical areas. Cortical columns were first reported by Vernon B. Mountcastlemm and colleagues in 1955 who described them as vertical clusters of cells, each about 500μm wide, that range across layers of the somatosensory cortex, and which contain cells responsive to single modalities (e.g., cutaneous receptors, deep joint receptors). Subsequently, he became known as the ‘Jacques Cousteau of the cortex‘. Mountcastle’s concept was widened to include a wide range of neural structures, and came to refer to cells in any vertical arrangement that share the same receptor function. One such well-publicized structure is that of ocular dominance columns,as originally portrayed by Hubel and Wiesel in 1969, the basic idea being that cells with the same eye preference are clustered into such columns. An outcome was the Hubel and Wiesel 7-point scale in which 1 denotes exclusively contralateral dominance cells, 4 indicating cells responding equally to both eyes, and 7 meaning exclusively ipsilateral dominance. Another claim emanating from their work in this context was that cells in columns compete for innervation of the visual cortex during a critical period in mammalian development. This claim has been challenged, with evidence that columns in monkeys, cats and ferrets are initially established much earlier and without the necessary visual experience occurring during a critical period. A resolution has been to suggest that the foundation of the cortical architecture and the plasticity associated with ocular dominance during a critical period derive from different mechanisms. In fact, it has been suggested that cortical columns represent structures without functions. If this is the case, it is perhaps not too surprising that many species (e.g., squirrel monkeys) either lack or partially lack such columns. So, it may be the case that they are not a universal feature in the neuronal architecture of mammalians.
See Cortical column, Critical period, plasticity, Developmental plasticity, Primary visual cortex (V1), Secondary visual cortex (V2), Somatosensory cortex, Visual cortex