A study in Science has settled a decades‑long debate by showing that our brains continue to forge new neurons well into old age. Researchers at Karolinska Institutet used cutting‑edge single‑nucleus RNA sequencing, flow cytometry, and spatial gene‑mapping on human hippocampal tissue ranging from newborns to 78‑year‑olds to reveal active neural progenitor cells in the dentate gyrus—a clear sign of ongoing neurogenesis in adults.
By measuring gene expression in individual cell nuclei and training machine‑learning algorithms to trace developmental stages, the team distinguished stem cells through to immature neurons, many caught mid‑division. Two complementary imaging methods, RNAscope and Xenium, then pinpointed these progenitors to the dentate gyrus, the memory hub of the hippocampus.
“We have now been able to identify these cells of origin, which confirms that there is an ongoing formation of neurons in the hippocampus of the adult brain,” says Jonas Frisén, Professor of Stem Cell Research at Karolinska Institutet.
Although similar progenitor populations exist in rodents and primates, human brains showed unique patterns of gene activity—and striking individual differences, with some adults hosting plentiful neural progenitors while others had very few.
“This gives us an important piece of the puzzle in understanding how the human brain works and changes during life,” Frisén explains.
The discovery not only resolves a fundamental question about brain plasticity but also opens doors for therapies aimed at stimulating neurogenesis in neurodegenerative and psychiatric disorders, offering fresh hope for regenerative medicine.
The study has been published in Science.
