Dendritic development in human occipital cortical neurons.

Using quantitative techniques on rapid Golgi impregnations, the dendrites from neurons of visual cortex from 14 infants ranging in age from 20 weeks gestation to 7 years were assessed. Neurons in layers 3 and 5 were separately evaluated. The total dendritic length for all dendritic branches reached a maximum of 2800 microns for layer 3 neurons and 3400 microns for layer 5 neurons. At or before 40 weeks gestation, the dendritic tree of layer 3 neurons had reached 35% of the maximum compared with 55% of the maximum for layer 5 neurons. Dendritic branching occurred earlier in layer 5 and growth continued to be more advanced than in layer 3. After 40 weeks gestation in these layers no new branch orders were added to basal dendrites but 3 branch orders were added to apical dendrites. The determination of normal values for dendritic length, number of orders, and number of branches during early development provides a foundation for comparison of dendritic maturation in children with a variety of neurologic disorders.