Figure 1. There is a neuronal birthdate gradient within the chick optic tectum.

Previous birthdating studies [5] revealed a lateral rostroventral to medial caudodorsal birthdate gradient within the optic tectum. The lateral to medial dimension is not represented here. Taking advantage of this birthdate gradient, we looked for FGF2-induced differences in cell cycle exit in the rostroventral tectum at the beginning of tectal neurogenesis and in the caudodorsal tectum at the end of tectal neurogenesis.