For the first time in history, a team of Spanish researchers have proved that brand-spanking-new neurons are continually created even into the ninth decade of life. This was observed within a part of the brain called the dentate gyrus located within the hippocampus. The hippocampus is one of the primary reasons we can remember our experiences, as it is the short-term storage house for memories.

It’s also one of the first regions to suffer from the onset of dementia and other neurodegenerative diseases like Alzheimer’s. Until recently, there was no evidence that adult hippocampal neurogenesis occurred in humans.

The Spanish scientists demonstrated that not only are new immature neurons being formed in the dentate gyrus until very late in life, but that this neurogenesis was notably absent in brain tissue samples from patients with Alzheimer’s. According to the study, the fact that humans can grow completely new neurons even in old age gives us a remarkable degree of neuro-plasticity – a term used to describe brain capabilities and flexibility.

If Alzheimer’s disease prevents the hippocampus, the depot for short-term memories, from generating new neurons, this could likely explain the Alzheimer’s panoply of symptoms. This discovery could open an entire new avenue of physiological and pathological understanding of neurodegenerative disease treatment and understanding.

A common tall-tale

This exciting new discovery goes completely against the common claim that your brain doesn’t fully develop until 25 or 29. This phrase is now demonstrably false and misrepresentative of the complexity of the brain.

“Proliferation of neural precursors during cortical development ends much earlier. As far as we know at the present moment, there is no proliferation of neural progenitors in the cortex at elder ages,” said María Llorens-Martín, one of the authors of the new paper in response to inquiry from World At Large.

The neural cortex is a large region of the brain responsible for many actions, including the long term storage of information. Certain regions of the neural cortex are also victims of Alzheimer’s insidious grasp like the hippocampus.

“Each part of the brain develops at a different speed. However, apart from the so-called neurogenic regions, as far as we know, other brain areas do not generate new neurons throughout lifetime. I believe that “developing” refers to the formation of circuits and connections between neurons, rather than to the generation of new neurons per se.”

“We have checked the presence of immature neurons in some non-neurogenic regions of the brain (not in all of them). But in the areas we have studied (namely, the CA1, and the CA3 hippocampal subfields and the Entorhinal cortex) we have not found the presence of immature neurons. This is totally different to what we observed in the dentate gyrus, where we detected an abundant presence of these cells.”

“The dentate gyrus (a region of the hippocampus) is one of those few regions that generates new neurons throughout lifetime. Our study demonstrates that many immature neurons are visualized in this structure of healthy human subjects until the ninth decade of life. Moreover, we observe a sharp decrease in the number of cells detected in Alzheimer´s disease patients.”