Adult Neurogenesis: Can We Grow New Brain Cells?

Growing new brain cells
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Conventional wisdom has long suggested that we cannot grow new brain cells; that we are born with all the brain cells we will ever have and that once those precious neurons expire, they're gone for good.

How true is this idea? Is it ever possible to grow new brain cells?

While the vast majority of the brain's cells are formed during prenatal development, there are certain areas of the brain that continue to create new neural cells – a process known as neurogenesis – during infancy.

Perhaps even more surprising, there is at least one important area of the brain that continues to create new cells throughout the entire lifespan.

During the 1990s, researchers conducted studies that involved injecting participants with a compound that is taken up into a cell's DNA. The researchers discovered that the hippocampus – a region of the brain associated with memories, learning, and emotions – continues to create new cells well into old age.

Later studies using carbon-14 dating,  a technique used for measuring  the age of a cell, allowed researchers to further demonstrate that the human hippocampus generates new cells. Cells in the hippocampus are also continually dying. The formation of new nerve cells allows the hippocampus to maintain a balance, although the number of cells usually does begin to decline with age.

Why is the formation of new brain cells such an important discovery?

Researchers believe that it raises the possibility of treating degenerative brain diseases including Alzheimer's and Parkinson's. It may also mean that one day scientists can develop new treatments for brain trauma and injury.

While there have been indications that the brain grows new cells for decades, it wasn't until recently that research has confirmed these suspicions.

Why did the idea that the brain was largely set in stone after birth persist for so long? Partly because many people believed that in order to form lasting memories and store information over a long period of time, it was essential that the brain be relatively stable.

Today, we recognize that adult neurogenesis is not only possible, it is a regular occurrence.

Factors That Might Influence the Formation of New Brain Cells

It turns out that exercise is not just good for your body; it might also be good for your brain. In experiments with rats, researchers also found that aerobic exercise could lead to increased cell production in the hippocampus. Not only did the exercising rats grow more brain cells than rats that were not exercised, they were also smarter as well. Some research with human participants also suggests that exercise can lead to increased neurogenesis in people.

In addition to exercise, researchers have also found that enriched learning environments can also help contribute to the survival and integration of new brain cells.

Not surprisingly, age does play a role in neurogenesis. Researchers have found that the formation of new cells is greatly reduced in the hippocampal region of older animals. Since neurons are regularly dying as well, reduced production of new cells can lead to a gradual depletion of hippocampal neurons. By the time many adults reach their 80s, they may have lost as much as 20 percent of the neural connections in this region of the brain. Those who exhibit such loss also tend to display lower performance on memory tests.

The Bottom Line: Your brain continues to produce new neurons even as you age.

References

Creer, D. J., Romberg, C., Saksida, L. M., van Praag, H., Bussey, T. J. (2010). Running enhances spatial pattern separation in mice. Proceedings of the National Academy of Sciences in the United States of America. doi: 10.1073/pnas.0911725107

Kolata, G. (1998, March 17). Studies find brain grows new cells. The New York Times. Retrieved from http://www.nytimes.com/1998/03/17/science/studies-find-brain-grows-new-cells.html

Lazarov, O., Robinson, J., Tang, Y. P., Hairston, I. S, Korade-Mirnics, Z., Lee, V. M., Hersh, L. B., Sapolsky, R. M., Mirnics, K., Sisodia, S. S. (2005). Environmental enrichment reduces Abeta levels and amyloid deposition in transgenic mice. Cell, 120(5), 701–13. doi:10.1016/j.cell.2005.01.015

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