Neuronal growth cone as an integrator of complex environmental information.

Fundamental decisions on neuronal morphology and connectivity are made at the level of the neuronal growth cone. The decision to continue outgrowth in a given direction, to turn, to branch, or to stop growing seems in many cases to depend on the many signals received and integrated by the growth cone from its external environment. The role of the growth cone may be quite different over the course of a lifetime. During early development, growth cones connect large ensembles of initially spherical neuroblasts. Interpreting the molecular terrain to be traversed at this time presents a formidable task. The growth cone also emerges as the primary organelle of pathfinding and elongation in the regenerating adult nervous system. Finally, there is compelling evidence that the growth cone is not just associated with the formation of initial connections or restoration of broken connections, but is also a tool for neural plasticity in normal...