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Throughout life, new neurons are generated in the hippocampus, where they form a structure that supports memory creation. When new neurons are integrated into the hippocampus, they compete with existing cells, forging new synaptic connections that may weaken or replace older ones. As a result, high rates of hippocampal neurogenesis may drive the loss of information stored in existing circuits—i.e., forgetting. In many species, including mice and humans, rates of hippocampal neurogenesis are high during infancy and decline markedly over time. Consistent with the idea that hippocampal neurogenesis and forgetting are positively correlated, infancy in these species is also characterized by the absence of long-term memory formation. The correlation piqued the interest of Sheena Josselyn and Paul Frankland, neuroscientists at the University of Toronto and Hospital for Sick Children (both in Toronto, Canada): “This inverse relationship between the levels of neurogenesis and the ability to form a long-term memory got us thinking that maybe one is due to the other,” Josselyn told The Scientist.
Lab Anim. (NY) 43, 223 (2014).
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