Adult Brain Continues Making New Neurons

- The long-held scientific belief for most of the 20th century was that neurogenesis, the creation of new neurons, stopped after birth. Evidence challenging this dogma first emerged in animals in the 1980s, with the first significant proof in humans reported in 1998. - The term "super-agers" refers to individuals 80 years or older whose memory performance is comparable to that of people 20 to 30 years younger. Their brains also shrink at a significantly slower rate—losing about 1.06% of volume annually compared to 2.24% in their typically-aging peers. - Compared to healthy older adults, super-agers produce new neurons in the hippocampus at double the rate. In contrast, individuals diagnosed with Alzheimer's disease or showing early-stage cognitive decline exhibit negligible to almost no new neuron growth. - The primary site for this adult neurogenesis is the dentate gyrus, a part of the hippocampus critical for learning, memory formation, and mood regulation. - To track the active growth of new brain cells, researchers identify and follow three distinct developmental stages: stem cells, which can become neurons; adolescent "neuroblasts"; and newly formed immature neurons. - One innovative method used to confirm that new neurons are made in adulthood was developed by a research group at Sweden's Karolinska Institutet. They measured residual carbon-14, a byproduct of mid-20th-century nuclear bomb tests, in the DNA of brain cells to accurately determine when the cells were generated. - These new neurons are believed to play a crucial role in "pattern separation," the brain's ability to distinguish between very similar memories, such as remembering where you parked your car today versus yesterday.