[Comparison of the field formation in the frontal area during prenatal period in Macaca (Macacus rhesus, S. Macaca mulatta) and man].

A developmental comparison of the fields 8, 9, 10, 11, 12, 47 during prenatal life in macacus rhesus and man was performed. Cytomyeloarchitectonic and morphometric methods of investigation were applied: the areas of the fields in question, the transverse thickness of the cortex, separate cortical layers, neuronal dimentions were measured. Alongside, general regularities in the development of these fields in both species (the frontal cortex is laid earlier than other parts of the cortex, the terms of the field differentiation coincide, uneven development of the fields with different phylogenic origin) some important differences are demonstrated. They are seen a) in the rate of the frontal field maturation--in man it takes longer time, b) in a more complex organization of the frontal part in man--during prenatal life new structural features of the fields, 44, 45, 46 and subfields in the field 47 appear. During prenatal life of monkey and man in the development of the frontal area the phenomena of heterochrony (common for both species) and anabolia (peculiar for man only) are observed (the appearance of new more complex structures). These phenomena display themselves in the shift of the laying of the frontal area towards earlier stages of embryogenesis.