Scientists have long debated whether the aging human brain continues to generate new neurons and whether those neurons matter for cognition. A new perspective piece in Cell Stem Cell highlights landmark findings by Tosoni et al. showing that immature neurons persist in the aged dentate gyrus — the brain's key memory hub — and that their transcriptional programs (the pattern of genes they activate) are linked to Alzheimer's pathology and cognitive resilience. Crucially, it is not simply how many immature neurons are present, but the molecular state those neurons are in, that appears to track with how well the brain resists cognitive decline. This reframes how scientists think about adult neurogenesis, suggesting these cells may serve as active support partners for brain health rather than mere replacements for lost neurons.
