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.
