Can an adult human brain make new neurons? Evidence increasingly supports that it can in the hippocampus, but that answer leaves important questions: how many cells are produced, how they mature and what they contribute to memory or disease. The research has moved beyond the simple opposition between a permanently fixed brain and one that endlessly replaces itself.
Why the question became controversial
In 1998, Eriksson, Gage and colleagues examined postmortem tissue from people who had received BrdU, a substance incorporated into DNA during cell division. Combining that label with neuronal markers supported the formation of new neurons in the adult dentate gyrus, part of the hippocampus.
Later findings did not always agree. Sorrells and colleagues’ 2018 study reported a steep childhood decline to undetectable levels in adults using its methods. By contrast, Moreno-JimĂ©nez and colleagues in 2019 identified many immature neurons in carefully processed adult samples, with fewer and altered maturation in Alzheimer’s disease.
Those findings cannot be reconciled merely by declaring one laboratory’s methods âbetter.â Tissue processing, the specificity of markers and the distinction between an immature cell and a newly born cell all matter. Looking at donated tissue also differs from following a cell’s entire development in a living person.
What newer work adds
A 2025 Science study from Karolinska Institutet combined several methods, including analysis of gene activity in individual nuclei and spatial techniques. The team identified proliferating neural progenitors in the adult hippocampus, providing evidence for cells from which new neurons can develop. Numbers varied substantially between individuals.
In February 2026, Disouky and colleagues reported a further study in Nature. They analysed 355,997 nuclei from postmortem hippocampal samples across groups differing in age, cognition and Alzheimer’s pathology. These are cell nuclei, not 355,997 participants.
The researchers identified neural stem cells, neuroblasts and immature neurons, and compared their molecular profiles. They found differences associated with Alzheimer’s pathology and with exceptional memory in older adults. Such associations help identify mechanisms for further study; they do not establish that increasing neurogenesis will prevent dementia.
Why this is not yet a prescription
Three questions are easily collapsed into one: whether cells exist, whether they make a functional contribution and whether a treatment can safely improve that contribution. A positive answer to the first does not automatically answer the other two.
Likewise, a result in rodents cannot be turned directly into a claim that a particular human exercise routine or supplement grows a specified number of neurons. This article does not offer a neurogenesis âboostingâ protocol or recommend changing treatment.
The more useful picture
Neurogenesis means generating neurons. It should not be used as a synonym for every kind of brain plasticity, which also includes changes involving existing cells and connections. The presence or absence of one process is not a verdict on whether adults can learn.
The interesting development is that different tools now offer complementary evidence. The next challenge is understanding the scale and consequences of the process, rather than treating every new result as permission to announce either a miracle or a final reversal.
Editorial review: 10 September 2026. Added 2025 and 2026 research, corrected attribution and chronology, and removed an unverified meta-analysis citation and unsupported therapeutic inferences.
