Prefrontal cortex in humans and apes: a comparative study of area 10.
Area 10 is one of the cortical areas of the frontal lobe involved in higher cognitive functions such as the undertaking of initiatives and the planning of future actions. It is known to form the frontal pole of the macaque and human brain, but its presence and organization in the great and lesser apes remain unclear. It is here documented that area 10 also forms the frontal pole of chimpanzee, bonobo, orangutan, and gibbon brains. Imaging techniques and stereological tools are used to characterize this area across species and provide preliminary estimates of its absolute and relative size. Area 10 has similar cytoarchitectonic features in the hominoid brain, but aspects of its organization vary slightly across species, including the relative width of its cortical layers and the space available for connections. The cortex forming the frontal pole of the gorilla appears highly specialized, while area 10 in the gibbon occupies only the orbital sector of the frontal pole. Area 10 in the human brain is larger relative to the rest of the brain than it is in the apes, and its supragranular layers have more space available for connections with other higher-order association areas. This suggests that the neural substrates supporting cognitive functions associated with this part of the cortex enlarged and became specialized during hominid evolution.