Fig. 3. The stages of morphological development of dendrites and dendritic spines.

A: Immature neurons have shorter dendrites, and these dendrites have no spines. B: During synaptogenesis and neuronal maturation, neurons develop a more complex dendritic arbor, and these dendrites begin to form spines. Some of these spines start to receive input from the axons of other neurons. C: Mature neurons have elaborate dendritic trees and a high density of mature spines. These neurons form functional connections with other neurons and participate in the brain circuitry.