Formation of new brain cells can erase old memories

Over the past ten years it has been established that generation of new nerve cells in the dentate gyrus portion of our brains' hippocampus is required for hippocampus dependent learning and memory recall. Akers et al. now show that this neurogenesis may also promote forgetting. So, it would appear that while not enough neurogenesis inhibits learning and enhanced neurogenesis enhances it, the ongoing circuit remodeling caused by higher neurogenesis can also make the memories more laible. Thus, there may be a compromise “trade-off” level of neurogenesis that allows good performance for both memory acquisition and retention. The abstract:

Throughout life, new neurons are continuously added to the dentate gyrus. As this continuous addition remodels hippocampal circuits, computational models predict that neurogenesis leads to degradation or forgetting of established memories. Consistent with this, increasing neurogenesis after the formation of a memory was sufficient to induce forgetting in adult mice. By contrast, during infancy, when hippocampal neurogenesis levels are high and freshly generated memories tend to be rapidly forgotten (infantile amnesia), decreasing neurogenesis after memory formation mitigated forgetting. In precocial species, including guinea pigs and degus, most granule cells are generated prenatally. Consistent with reduced levels of postnatal hippocampal neurogenesis, infant guinea pigs and degus did not exhibit forgetting. However, increasing neurogenesis after memory formation induced infantile amnesia in these species.