Principles of the Tetrapartite Model of Pallial Development and Evolution

1. The cerebral cortex originates from four Fundamental Morphological Units (FMUs) specified in the alar plate of the peduncular hypothalamic prosomere

2. The four FMUs that originate the cerebral cortex (medial, ventral, lateral, and dorsal pallia) are identified across fish, amphibia, reptiles, birds, and mammals

3. The olfactory allocortex originates form the ventral pallium and the hippocampal allocortex, including the entorhinal cortex, originates from the medial pallium

4. Mesocortical (neocortex non sensu stricto) and isocortical (neocortex sensu stricto) areas of mammals originate from lateral and dorsal pallia

Principles of the updated hypothesis on the dual origin of the neocortex

5. Allocortical, mesocortical, and isocortical areas in adult brains are topologically arranged in concentric rings across mammals. The allocortex is the outermost ring and the isocortex is the innermost ring. The mesocortical ring lies between the allocortex and the isocortex

6. Neocortical (mesocortical and isocortical) areas show progressive laminar elaboration across gradients that start in periallocortical (agranular mesocortical) areas and progress through proisocortical (dysgranular mesocortical) areas into isocortical (eulaminate) areas

7. Two gradients of laminar elaboration are identified in the cerebral cortex of adult mammals: paraolfactory and parahippocampal. These gradients converge in eulaminate areas

8. Cortical types can be defined operationally across cortical gradients of laminar elaboration

9. Allocortical, mesocortical, and simple isocortical (eulaminate) types are identified in rats and in primates

10. Highly eulaminate types (eulaminate II, eulaminate III, and koniocortical areas) are identified in primates but do not have counterpart in rats

11. The qualitative and quantitative expansion of the primate isocortex emerges in development with progressive development of the outer subventricular zone (OSVZ) in prospective isocortical areas

12. Thus, according to 8, 9, and 10, gradients of laminar elaboration expand quantitatively and qualitatively in primates compared to rodents with the addition of highly eulaminate types

13. Two cortical areas in two mammalian species are likely homologues if they are in the same ring (cortical type) of cortex

14. Mesocortical areas and simple eulaminate areas in rats and primates are likely homologues. Highly eulaminate types (eulaminate II, eulaminate III, and koniocortical areas) in primates do not have homologues in rats

Principles of the structural model for cortical connections

15. Laminar patterns of cortico-cortical connections are related to cortical types

16. Cortical type predicts position of cortical areas across cortical hierarchies