The capacity that the axons of developing neurons have to select particular directions of migration. The first axons to migrate in the embryo are termed pioneering axons that serve as pathways for some, but not all, later developing axons to migrate to their target. They are guided by growth cones at their tips that respond to the presence or absence of growth cues (i.e., protein adhesion molecules) in the extracellular matrix. Such cues, recognised by receptors on the membrane of the growth cues, are either short- or long-range, and can be either attractive or repellant. Diffusible chemoattractive substances are secreted by the targets of developing axons, and help to guide the axons to the correct site for synaptic contact to be made. Cells located near the target neurons may also secrete a chemorepellant, resulting in axons being deflected away in the direction of their correct destination, or preventing them from overshooting it. The so-called guidepost cells indicate the end of one pathway, and the beginning of another.
See Adhesion molecules, Axon, Cell locomotion, Extracelluar matrix, Growth cone, Guidepost cells, Synapse elimination