Models of axon guidance and bundling during development

Diffusible chemoattractants and chemorepellants, together with contact attr action and repulsion, have been implicated in the establishment of connecti ons between neurons and their targets. Here we study how such diffusible an d contact signals can be involved in the whole sequence of events from bund ling of axons, guidance of axon bundles towards their targets, to debundlin g and the final innervation of individual targets. By means of computer sim ulations, we investigate the strengths and weaknesses of a number of partic ular mechanisms that have been proposed for these processes.