Categories of cortical structure

Publisher Summary The organization of the mammalian cortex is usually discussed in terms of maps and modules.Maps are topographic cortical (or subcortical) representations in which the geometry of the body is laid out in a more or less continuous fashion that reflects the arrangement of receptor surfaces or musculature. Modules are iterated structures within such maps whose significance and genesis has remained mysterious. These traditional distinctions have sometimes made it difficult to compare diverse cortical systems. For example, the primary somatic sensory map is not easily equated with the cortical map of visual space. Further, iterated modules of similar size and appearance in various cortical regions are not necessarily members of the same class. More useful categories for comparison are cortical structures generated by induction, recognition and subsequent trophic interactions, and iterated cortical units generated by the effects of neural activity on neuronal growth. This analysis of cortical development considers barrels in the somatic sensory cortex and entities such as the primary visual cortex to be members of the same category, and distinguishes barrels from activity-dependent structures such as ocular dominance columns.