Neurons Continue To Develop In The Human Brain Even In Old Age, Offering New Hope For Memory, Learning, And Repair

Researchers have discovered that the human brain continues to produce new neurons even into adulthood, particularly in an area involved in memory and learning called the hippocampus. Using cutting-edge techniques, they have identified dividing neural stem cells in people of different ages, proving that so-called “adult neurogenesis” really does occur. This discovery could open the door to new treatments for diseases such as Alzheimer’s and depression.

For a long time, scientists believed that the human brain stopped producing new neurons after childhood, becoming an essentially “fixed” organ in adulthood. This idea held that, after a certain age, the brain would progressively lose its ability to adapt and renew cells.

However, recent research is challenging this view, and a new study provides the most convincing evidence to date that the adult human brain continues to generate new neurons, a process known as adult neurogenesis.

Neurogenesis occurs in a specific region of the brain called the hippocampus, which is crucial for memory, learning and emotional control. The study, led by Dumitru and colleagues at Karolinska Institutet in Sweden, used highly advanced techniques to investigate the presence and activity of so-called neural progenitor cells, which are precursors to neurons.

The team analyzed samples of post-mortem human brain tissue, spanning an age range from birth to 78 years of age. Using a modern technique called single-nuclear RNA sequencing, which allows the genetic activity of individual cells to be examined, the researchers were able to identify all stages of neural cell development, including in adults.

To further enhance the accuracy of the data, the scientists also applied machine learning algorithms and used specific antibodies (such as Ki67, which marks actively dividing cells) to locate these progenitor cells in adults.

In addition, spatial transcriptomics tools such as RNAscope and Xenium were used to map exactly where these new cells were emerging, in the dentate gyrus, a subregion of the hippocampus closely linked to the creation of new memories and cognitive adaptation.

Interestingly, adult human neural progenitor cells were quite similar to those found in animals such as mice, pigs and monkeys, which reinforces the idea that the process of neurogenesis is conserved across species.

Schematic of the current view of lineage progression and fate decisions during adult hippocampal neurogenesis. A, astrocyte; GC, granule cell; NSC, neural stem cell. Image: Anja Urbach and Otto W. Witte.

However, the study also revealed important variations between human individuals: while some had large numbers of these dividing cells, others showed very low levels. This raises new questions about what might influence adult neurogenesis, genetic, environmental, lifestyle or medical conditions, for example.

These findings not only expand our understanding of how the human brain adapts and changes throughout life, but also open up promising avenues for the development of regenerative therapies.

In the near future, stimulating neurogenesis could become an important strategy in the treatment of neurodegenerative diseases (such as Alzheimer's) and psychiatric disorders (such as depression), helping to restore or improve brain function in a more natural and lasting way.

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Identification of proliferating neural progenitors in the adult human hippocampus

IONUT DUMITRU, MARTA PATERLINI, MARGHERITA ZAMBONI, CHRISTOPH ZIEGENHAIN, SARANTIS GIATRELLIS, RASOOL SAGHALEYNI, ÅSA BJÖRKLUND, KANAR ALKAS, MATHEW TATA, HENRIK DRUID, RICKARD SANDBERG, AND JONAS FRISÉN 

SCIENCE. 3 Jul 2025. Vol 389, Issue 6755. pp. 58-63

DOI: 10.1126/science.adu9575

Abstract: 

Continuous adult hippocampal neurogenesis is involved in memory formation and mood regulation but is challenging to study in humans. Difficulties finding proliferating progenitor cells called into question whether and how new neurons may be generated. We analyzed the human hippocampus from birth through adulthood by single-nucleus RNA sequencing. We identified all neural progenitor cell stages in early childhood. In adults, using antibodies against the proliferation marker Ki67 and machine learning algorithms, we found proliferating neural progenitor cells. Furthermore, transcriptomic data showed that neural progenitors were localized within the dentate gyrus. The results contribute to understanding neurogenesis in adult humans.