Structure and function of the human frontal lobe

Abstract

Cytoarchitectural and myeloarchitectural investigations of the human frontal lobe in adjoining serial sections of the same hemispheres pointed out as basic principle of architecture “gradations”, i.e. discontinous stepwise changes of architectural features in constant orientation. The gradations originating from phylogenetically older surrounding cortices as cingulate gyrus, basal olfactory cortex, insula and precentral motor cortex determine the structure of more recent prefrontal cortex. Therefore they represent directions of differentiations during evolution. What is generally called supplementary motor and secondary sensorimotor representation, appears to be the protomotor and protosensorimotor representation when considered in the light of the flow of the gradations. The classic motor representation appears contrariwise as a more recent achievement in phylogenesis. The relationship of the high frontal functions to the reticular core of the brain stem is discussed in the light of evolutional directions of differentiation. The orbital syndrome of impairment of personality in feeling and acting is considered as resulting from the special position of the orbital cortex in the system of gradations.