As mentioned previously, the brain is subdivided into areas of similarity to form a cytoarchitectonic map. While these areas tend to follow the gyri and sulci of the folded surface of the brain, the key feature of an area is that all of the cells in the cortex in that area are functionally similar. For example, the cells in Area 17, located in the occipital lobe, all receive input from the visual pathway. It is no simple coincidence therefore that Area 17 is called the primary visual cortex. Areas 18 and 19, located anterior to Area 17, are secondary or association visual cortex areas. Other important areas include Areas 22, 41, and 42, which make the primary and secondary audio cortex in the temporal lobe, Areas 1, 2, 3, 5 and 7 in the parietal lobe which are somatosensory cortex, and Areas 4 and 6 which are primary motor cortex.