neurons everywhere in the mammalian brain, including the cortex. However, other scientists continued to support Rakic's doctrine which denied the possibility of neurogenesis in mammals. Kaplan is reported as remembering Rakic telling him that “Those [cells] may look like neurons in New Mexico, but they don't in New Haven.” Like Altman before him, Kaplan abandoned his work in neurogenesis. Confronting Rakic's data Gould spent the next eight years quantifying endless numbers of radioactive rat hippocampi in pursuit of neurogenesis. Gould became a member of the Princeton faculty in 1997. The very next year, in a series of papers, Gould began documenting neurogenesis in primates, directly confronting Rakic's data. She demonstrated that adult marmosets created new neurons in their brains, especially in the olfactory cortex and the hippocampus. By 1999, Rakic admitted that neurogenesis was real. To that end he published a paper in the Proceedings of the National Academy of Sciences that reported seeing new neurons in the hippocampus of macaques. Current work Gould's laboratory at Princeton studies the production of new neurons in the early postnatal and adult mammalian brain. Her laboratory explores issues related to the regulation of cell production and survival in three brain regions the hippocampus, the olfactory bulb and the neocortex in rodents and primates (marmosets and macaques). Gould and her colleagues believe the answer to the question, ‘What possible function could late-generated cells serve?’ could have immense significance in neuroscience and their investigations are guided mostly by this question. Gould and her team are also endeavoring to discover how hormones modulate the production of new neurons and how experience affects new cell production and if so, through what underlying mechanisms. Research by Gould and her colleagues Hormonal regulation of cell production Gould and her colleagues found that the ovarian steroid estrogen enhances cell proliferation in the dentate gyrus of the adult rat. This effect can be seen following ovariectomy and hormone replacement as well as under naturally occurring changes in hormone levels. They discovered that cell proliferation peaks during proestrus, a time when estrogen levels are highest. Also and conversely, steroid hormones of the adrenal glands were found to inhibit cell proliferation in the dentate gyrus but do so indirectly via an NMDA receptor-dependent mechanism. Experience-dependent changes in neurogenesis Gould's research has shown that exposure of aversive stimuli results in a decrease in cell proliferation in the dentate gyrus of adult rats, tree shrews