Neurons in very few CNS populations continue to be produced during adulthood. The goal of our research is to understand the function of this adult neurogenesis by studying the regulation of neuronal precursor proliferation and survival in the dentate gyrus, a part of the hippocampal region in which large numbers of new neurons are born throughout adulthood. This year we investigated the effects of a natural form of learning on survival of newborn granule neurons in the adult dentate gyrus. Previous reports indicated that the survival of newborn granule neurons increases if hippocampus-dependent behavioral tasks are given to rats during the critical period of granule neuron development, between one and four weeks after cell birth. However, the tasks used previously are very difficult, requiring extensive training, and therefore are not good models for one function of the hippocampus, ?automatic recording of attended experience.? We examined the survival of new neurons following a natural learning task, social transmission of food preference (STFP), which is learned in a single trial. We found that one day of training for STFP increases survival of new neurons, as seen through increased numbers of 16-day-old cells labeled with the cell birth marker BrdU., as expected from the previous studies with difficult learning tasks. However, we found that two days of training decreased survival of 16-day-old cells. This switch from increased survival to increased cell death may provide a mechanism for storing information temporarily in the hippocampus and discarding cells when their stored information is no longer needed, in order to make space for new completely naive neurons.
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