Neuronal birthdate underlies the development of striatal compartments.

The striatum of the mammalian forebrain is composed of two complementary functional compartments, the patches and the matrix. By injecting [3H]thymidine at different embryonic times and sacrificing the rats as young adults, we found that the earliest neurons to leave the mitotic cycle were restricted to the patch compartment. Neurons that became postmitotic at later times preferentially joined the matrix compartment. Distinctive periods of cell proliferation may underlie pattern formation throughout the developing forebrain.