The cerebral cortex has been geometrically designed so that the locations of cortical structures and the connections between them allow for the greatest degree of association, both in integrating different areas of the cortex and in producing higher level abstractions.
Cortical columns in sensory areas (auditory, visual, somatosensory) form maps. Regions of cortex adjacent to these maps are associative, with the associations becoming progressively higher level and more abstract with greater distance from the sensory map. For instance, the intensities of different frequencies of sound waves are mapped on the planum temporalum, while cortical areas in more inferior areas of the temporal lobe process higher level information, starting with sounds and moving to word concepts.
Cortical columns in motor areas also form maps. Regions more anterior in the frontal lobe handle progressively higher level information. Because temporal precision is necessary for motor movements, the upper levels of the frontal lobe naturally develop the role of organizing events in time. Each higher level increases the length and complexity of structured sequences. Thus, the model proposes a plausible explanation for why the frontal lobes are involved in motivation and producing structured sequences.
According to our model, cortical division of function is a natural outcome of certain areas of cortex being mapped to certain extracortical functions, i.e. sensory and motor maps. As a result of the spreading activation of call trees, the areas adjacent to these maps assume the roles of progressively higher level integration and association units.
Therefore the cortex as a whole is minimally genetically determined; however, the locations of cortical maps are relatively constant. The associative regions corresponding to those maps naturally develop around them.