Roles of continuous neurogenesis in the structural and functional integrity of the adult forebrain

Neurogenesis occurs continuously in the forebrain of adult mammals, but the functional importance of adult neurogenesis is still unclear. Here, using a genetic labeling method in adult mice, we found that continuous neurogenesis results in the replacement of the majority of granule neurons in the olfactory bulb and a substantial addition of granule neurons to the hippocampal dentate gyrus. Genetic ablation of newly formed neurons in adult mice led to a gradual decrease in the number of granule cells in the olfactory bulb, inhibition of increases in the granule cell number in the dentate gyrus and impairment of behaviors in contextual and spatial memory, which are known to depend on hippocampus. These results suggest that continuous neurogenesis is required for the maintenance and reorganization of the whole interneuron system in the olfactory bulb, the modulation and refinement of the existing neuronal circuits in the dentate gyrus and the normal behaviors involved in hippocampal-dependent memory.

神经发生在成年哺乳动物的前脑中持续进行，但成年神经发生的功能重要性仍不明确。在此，我们利用成年小鼠的一种基因标记方法发现，持续的神经发生导致嗅球中大多数颗粒神经元被替换，以及海马齿状回中大量颗粒神经元的增加。对成年小鼠新形成的神经元进行基因消融，导致嗅球中颗粒细胞数量逐渐减少，抑制齿状回中颗粒细胞数量的增加，并损害已知依赖海马的情境记忆和空间记忆行为。这些结果表明，持续的神经发生对于嗅球中整个中间神经元系统的维持和重组、齿状回中现有神经回路的调节和细化以及海马依赖性记忆所涉及的正常行为是必需的。