Long-lived adult-born hippocampal neurons promote successful cognitive aging

Aging is commonly associated with a decline in memory abilities, yet some individuals remain resilient with preserved memory abilities. Memory processing is critically dependent on adult neurogenesis, a unique form of plasticity in the hippocampus. However, it remains unknown if cognitive aging influences the integration and role of adult-born hippocampal neurons (ABNs) generated early in adult life. Here, we investigated the role of long-lived ABNs in rats characterized as either resilient or vulnerable to cognitive aging using a peudo-longitudinal approach. Our findings reveal that long-lived ABNs support successful cognitive aging by preserving their synaptic inputs onto the proximal segments of their dendrites, and that these proximal synaptic sites also demonstrate a maintenance of their mitochondrial homeostasis. Furthermore, by-passing the reduced inputs of ABNs in vulnerable rats through direct optogenetic stimulation successfully improved their memory abilities. Overall, our data indicate that the maintenance of long-lived ABNs integration within the neuronal network is essential for successful cognitive aging, highlighting their potential as a therapeutic target for restoring cognitive functions in old age.