Stem cells and the cellular organization of the brain

The modern field of neuroscience emerged in the hands of neuroanatomists at the end of the last century. They recognized that information flows through arrays of cells and that the structure of the cells shapes the passage of information through the brain. In the middle of this century, the role of ion flux in the movement of information along axons was established. The electron microscope and the microelectrode helped to explain information transfer at the synapse, and study of the modulation of synaptic strength is currently a major area of neuroscience research. The origin of the many types of neuron seen by the early anatomists remains enigmatic, but the solution to this mystery is now emerging. The identification of stem cells and of the mechanisms that control their differentiation into distinct neuron types will contribute to a new understanding of both the origin of neuronal types and neuronal circuits. The current enthusiasm for stem cells is stimulated by interest from both the academic and nonacademic communities. These enthusiasts recognize a simple truth, that the cells are smart; they are the agents that control cell number and type in the brain. They create the structure that generates the higher order brain function. If these premises are true, then in the new century our understanding of the nervous system will be transformed by the facts of stem cell biology. J. Neurosci. Res. 59:298-300, 2000. Published 2000 Wiley-Liss, Inc.