Adult newborn neurons are involved in learning acquisition and long-term memory formation: the distinct demands on temporal neurogenesis of different cognitive tasks.

There is evidence that adult hippocampal neurogenesis influences hippocampal function, although the role these neurons fulfill in learning and consolidation processes remains unclear. Using a novel fast X-ray ablation protocol to deplete neurogenic cells, we demonstrate that immature adult hippocampal neurons are required for hippocampal learning and long-term memory formation. Moreover, we found that long-term memory formation in the object recognition and passive avoidance tests, two paradigms that involve circuits with distinct emotional components, had different temporal demands on hippocampal neurogenesis. These results reveal new and unexpected aspects of neurogenesis in cognitive processes.