Postnatal maturation of layer V pyramidal neurons in the human prefrontal cortex. A quantitative Golgi analysis.

The pattern of dendritic development of layer V pyramidal neurons in the human prefrontal cortex was studied quantitatively. The main objective was to determine how dendritic growth and differentiation continued postnatally. In order to do this, we analyzed the three-dimensional branching pattern of the basal dendritic field of Golgi-Cox impregnated neurons. The subjects ranged in age from 7.5 months after birth up to 27 years. The results revealed a maturational time-course with a rapid dendritic growth phase during the first postnatal year. The dendritic length and radial extension of the basal field increased. The growth continued, at a reduced rate, up to around 5 years of age by a lengthening of the terminal segments and a slight increase in soma size. The morphological maturation of the layer V pyramidal neurons was completed between one and five years. After this age the dendritic values appeared to level off and reach a stable level that lasted up to at least 27 years. This paper gives no indications for overgrowth or regressive events of the layer V basal dendritic trees during development.