The Regulation of Sprouting in the Adult Hippocampus: Some Insights from Developmental Studies

Sprouting, the reinnervation of partially denervated targets by residual afferents, has been observed in a number of brain areas in a variety of species (see Gall and Lynch 1980). The existence of this phenomenon has led to general acceptance of the idea that intact axons in the mammalian central nervous system retain some capacity for growth well into adulthood. However, recent studies have emphasized that sprouting in the adult is restricted in its extent and rather sluggish in its time course; these apparent limitations on the sprouting response raise a number of questions as to the nature of the factors which initiate, direct, and shape growth in the adult brain.