Neurons largely stop growing in the human brain between the ages of seven and thirteen, with very few new neurons appearing after that point, and none found in adult samples in one particular study.
This answer reflects findings challenging earlier beliefs about neurogenesis (the creation of new neurons) in adult human brains. Here's a more detailed explanation:
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Early Brain Development: Neurogenesis is most active during prenatal development and early childhood. This is when the brain rapidly forms the vast network of neurons needed for basic functions.
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Decline in Neurogenesis: Research suggests a sharp decline in neurogenesis in most brain regions as children age. One study indicated a significant reduction in new neuron formation between the ages of 7 and 13.
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Controversial Topic: The question of adult neurogenesis in humans has been a subject of ongoing debate and conflicting research findings. Some studies have suggested that neurogenesis continues in specific brain regions, such as the hippocampus (involved in memory) throughout adulthood. However, these findings have been challenged, with other research failing to replicate the results.
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Key Findings and Skepticism: The study referenced in the original prompt found very few young neurons present in the brain tissue of individuals between seven and thirteen years old and found no evidence of neurogenesis in adults. This study supports the view that neurogenesis is extremely limited, or nonexistent, in adult human brains, particularly outside of highly specialized areas.
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Implications: Understanding when and where neurogenesis occurs (or doesn't occur) has significant implications for research into neurological disorders, brain injury, and aging. If the brain's capacity to generate new neurons is limited, strategies to protect and preserve existing neurons become even more critical.
In summary, while the exact timeline of neurogenesis cessation is still an area of active research, the consensus leans towards a substantial decline in most brain regions by the time a person reaches adolescence, with some evidence suggesting little to no new neuron formation in adults.
