Basic research using cell transplantation indicates that structural developmental mechanisms seen in immature brains can also function in the adult brain. As the brain matures, cellular migration and axonal growth is impeded. However, fetal neural transplantation studies have shown that directional cues are available for fetal axons to find specific host neurons in the adult brain. By reaching specific and distant CNS target zones, donor tissue with extended axonal growth periods demonstrate both an abundance and specificity of CNS neurotropic signals. The presence of specific guidance cues, despite strong inhibition of regenerative long-distance axonal growth, suggests that these cues play other physiological roles in the adult CNS, and could be utilized therapeutically for reconnection of neuronal pathways.