Assembly of a Neural Circuit

Abstract

Precise connections established between synaptic partners are essential for the proper function of neural circuits. To explain the striking target specificity of the optic nerve during regeneration, Roger Sperry proposed the chemoaffinity hypothesis 50 years ago, which posits that developing neurons must carry “individual identification tags,” presumably cytochemical in nature. By this means, they can almost be distinguished in many regions, to the level of the single neuron (1). Since then, many molecules have been identified that guide axons to their final target area, but little is known about molecules that mediate mutual selection and matching between individual pre- and postsynaptic partners among many possible alternatives at the target area (2–4).