Organization of the Cortex

The cerebral cortex, also known as the isocortex or neocortex, consists of two hemispheres, each divided into five lobes that correlate with the main functional systems. It is organized into six uniform layers that contain different cell densities and types of neurons. Brodmann discovered various areas that are distinguished by unique combinations of cell types, densities, and layers, and correlate with functional differences. The cortex exhibits a map-like organization, where similar information is represented at adjacent locations, and a radial organization in micro and macro columns. These columns are possibly fundamental units of information processing and are involved in population coding. Retinotopy, tonotopy, and somatotopy are examples of the map-like organization of the cortex, reflecting different receptor densities and sensitivities of body regions. The canonical circuit of the cortex describes an information flow pattern in which ascending, descending, and horizontal connections between cortical areas are distinguished. The analysis of these connections reveals a hierarchical-parallel organization with multiple areas at each level and the hippocampus at the top of the sensory area hierarchy.