Synaptic development of layer V pyramidal neurons in the prenatal human prefrontal neocortex: a Neurolucida-aided Golgi study

The prefrontal neocortex is involved in many high cognitive functions in humans. Deficits in neuronal and neurocircuitry development in this part of the cerebrum have been associated with various neuropsychiatric disorders in adolescents and adults. There are currently little available data regarding prenatal dendrite and spine formation on projecting neurons in the human prefrontal neocortex. Previous studies have demonstrated that Golgi silver staining can identify neurons in the frontal lobe and visual cortex in human embryos. In the present study, five fetal brains, at 19, 20, 26, 35, and 38 gestational weeks, were obtained via the body donation program at Xiangya School of Medicine, Central South University, China. Golgi-stained pyramidal neurons in layer V of Brodmann area 46 in fetuses were quantitatively analyzed using the Neurolucida morphometry system. Results revealed that somal size, total dendritic length, and branching points of these neurons increased from 26 to 38 gestational weeks. There was also a large increase in dendritic spines from 35 to 38 gestational weeks. These findings indicate that, in the human prefrontal neocortex, dendritic growth in layer V pyramidal neurons occurs rapidly during the third trimester of gestation. The use of human fetal brain tissue was approved by the Animal Ethics Committee of Xiangya School of Medicine, Central South University, China (approval No. 2011-045) on April 5, 2011.