A landmark study published in the latest issue of Science delivers compelling evidence that the human brain retains the ability to generate new neurons – a process called neurogenesis – throughout life, even into old age. This discovery centers on the hippocampus, a brain region vital for learning, memory formation, and emotional regulation.
The research, spearheaded by scientists at the Karolinska Institutet in Sweden, addresses a core and persistent debate in neuroscience: whether the adult human brain possesses significant plasticity through the ongoing birth of new neurons. While a highly influential 2013 study by Professor Jonas Frisén's team at the same institute suggested adult hippocampal neurogenesis by measuring carbon-14 levels in brain DNA to date cell formation, the lack of direct proof for active "neural precursor cells" (the source of new neurons) left room for skepticism.
This new study provides that missing evidence. The team meticulously analyzed brain tissue samples from individuals aged 0 to 78 years, sourced from multiple international biobanks. They employed sophisticated methods:
Single-nucleus RNA sequencing (snRNA-seq): To analyze gene activity within individual cell nuclei.
Flow cytometry: To study cell characteristics.
Machine learning algorithms: To track the developmental journey of neurons from stem cells to immature stages and identify distinct subpopulations of cells still undergoing division.
Spatial transcriptomics (RNAscope & Xenium): To precisely locate where specific genes were active within the brain tissue structure.
The results were conclusive: active neural precursor cells and ongoing neurogenesis were identified, predominantly concentrated within the "dentate gyrus" region of the hippocampus. This area is crucial for forming new memories, learning, and cognitive flexibility.
Key findings include:
Human adult neural precursor cells share similarities with those found in mice, pigs, and monkeys but exhibit distinct genetic activity profiles.
Significant individual variation: Some adult samples showed abundant neural precursor cells, while others had levels approaching zero.
Professor Jonas Frisén emphasized the study's significance, stating it provides a "crucial piece of the puzzle" for understanding how the human brain changes and adapts over a lifetime. Beyond resolving a fundamental scientific question, the findings open promising new therapeutic pathways. They suggest the potential for developing regenerative treatments for neurodegenerative diseases (like Alzheimer's) and psychiatric disorders by finding ways to stimulate or support the brain's inherent neurogenesis mechanisms to repair damaged functions.
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