Hippocampal Neurogenesis: A Proposed Method for Human Testing
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For decades, the postulation of Cajal and Golgi that no new postnatal neurons were created in the brain formed the central dogma of neuroscience (Colucci-D’Amato, 2006). However by the 1960’s, researcher Joseph Altman was able to identify neural mitosis in adult rat olfactory bulbs and the dentate gyrus of the hippocampus using 3H-thymidine autoradiography (Jacobs 2001). Through the 1970’s and 1980’s it was confirmed that the newly formed cells in the dentate gyrus of adult rats were indeed neurons (and not glia cells) though more attention was given to neurogenesis studies in non-mammalian brains such as songbirds, fish and reptiles (Gould, 2002). Particularly important was the work of Fernando Nottebohm who demonstrated that newly proliferated neurons in adult songbirds were incorporated into the existing neural network, and that neurogenesis could be affected by an interaction between endogenous hormonal changes and external changes in the environment and social interactions (Colucci-D’Amato, 2006,). In the 1990’s the work of Elizabeth Gould, Fred Gage and many others incorporated the thymidine analog bromodeoxyuridine (BrdU), which allowed for the in vivo visualization of proliferating cells via immunocytochemical methods. BrdU labeling research led to the confirmation of Hippocampal neurogenesis and cellular migration in adult rodents, tree shrews, monkeys and even humans (Gould, 2002; Jacobs 2001). The purpose of this paper is to create a functional experimental paradigm for examining neurogenesis in adult humans. To that end I will review several key areas of research that have led to important findings regarding the neurogenesis phenomena, findings which will form a valuable foundation for the components of the experimental design.