1. A method of identifying a neurogenic agent, which comprises: (a) providing a stable human neural progenitor cell line, wherein (i) the cell line is derived from the hippocampus, (ii) the cell line has been expanded for at least ten cell doublings without substantially differentiating, and (iii) the cell line is capable of generating at least 40% neurons upon differentiation by mitogen withdrawal; (b) plating undifferentiated cells of said cell line into a culture with a serum-free, mitogen-free medium; (c) contacting the cells with a test agent which is a fused imidazole, an aminopyrimidine, a nicotinamide, an aminomethyl phenoxypiperidine or an aryloxypiperidine; (d) incubating the cells in the presence of the test agent for 3-7 days; (e) quantitatively determining the formation of neurons from said cells; and identifying the test agent as a neurogenic agent if said test agent increases the number or proportion of neurons by at least ten percent (10%).