The discovery that healthy, older adults produce just as many new neurons reverses a long-held theory about how our brains grow old and it provides us with some new ideas about how we might keep our brains young and agile.
Brain health is an important topic for people once they hit middle age. Like so many aspects of our bodies, it is mostly taken for granted until we notice the first signs of aging.
When it comes to our brains, conventional wisdom long had it that we were born with a certain number of brain cells or stopped making new brain cells after infancy, and that was what we had to work with for life. Research is accumulating that challenges that belief. While it appears to remain true for other mammals like rodents and primates that the ability to renew brain cells declines greatly after birth, there is emerging research that suggests the news is much better for humans. 1
One of the most promising studies in humans about the creation of new neurons in the adult brain, called “neurogenesis,” came from a team at Columbia University. 2 As Dr. Maura Boldrini, lead author explained in an interview on Science Friday, there have been conflicting conclusions in other studies about neurogenesis in adult human brains, but the studies mostly used preserved specimens from brain banks and did not account for the effects of disease, medications, and even mental health conditions. 3
In contrast, the Columbia team analyzed “clean brains” from “healthy aging individuals” age 14-79 who experienced sudden death from accidents or heart attacks. Brain tissue was analyzed within 24 hours after death and in addition to analysis of brain cells, the team performed what they call a “psychological autopsy,” gathering “extensive clinical evaluations, including interviewing families and close contacts, and reviewing the charts.” 3
The Columbia team found “that healthy older men and women can generate just as many new brain cells as younger people.” 1 The team did find “older people had less neuroplasticity, meaning their brain was less able to rearrange its connections in this area.” 4 Dr. Boldrini said the team also found less vascularization and fewer capillaries in the brains of older individuals, “So even though these people were not affected by any dementia or memory problems, there is some vulnerability that comes even with a normal aging.” 3
Most recently, research published by a team in Spain provided strong support for the work at Columbia. Elena P. Moreno-Jimenez and colleagues at the Autonomous University of Madrid analyzed brain tissue preserved for less than 24 hours6 and “reported the presence of thousands of new neurons (43,000 neuroblasts/mm2, depending on age) in the hippocampus of healthy people aged 43–87 years. Tissue samples from people who died and had Alzheimer’s disease presented less neuroblasts in the dentate hippocampal gyrus, indicating that even the new neurons formed by adult neurogenesis die in this type of dementia. This seminal paper confirmed previous studies reported by Boldrini et al. (2018) as well as the initial findings by Spalding et al. (2013).” 7
A writer at Science magazine was kind enough to sort through the complex issues that explain the basis for why the Columbia and Madrid teams were able to provide strong evidence to support the controversial concept, what she called “one of the thorniest debates in neuroscience…whether people can make new neurons after their brains stop developing in adolescence.” 8 In looking at the methodology of studies that had disproved the process of neurogenesis in adult humans, many studies used samples from brain banks that have been preserved in paraformaldehyde for extended periods of time. It turns out that paraformaldehyde “forms bonds between the components that make up neurons turning the cells into a gel” which makes it difficult to detect new neurons. 8
There is enthusiasm in some corners of the neurology world that this new understanding of adult neurogenesis in the brain will lead to therapies for both acute and chronic neurological disorders.7 It is certainly work that we will continue to follow and share developments as we see them.
In the meantime, you can work on growing some new brain cells:
References
1Cell Stem Cell. Older Adults Grow Just as Many New Brain Cells as Young People. Press Release. 5 April 2018. Science Daily. https://www.sciencedaily.com/releases/2018/04/180405223413.htm
2Boldrini M et al. Human Hippocampal Neurogenesis Persists throughout Aging. Cell Stem Cell. 2018 Apr 5;22(4):589-599. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5957089/
3Science Friday. Do Our Brains Keep Growing as We Age? 6 April 2018. https://www.sciencefriday.com/segments/are-aging-brains-still-growing/?fbclid=IwAR23I6_dIbtf-IJ5kNoekqXPid2y_SzzEsddgkpwK-vC4Tzpn4glpjFDgrg
4Thompson H. Old People Can Produce as Many New Brain Cells as Teenagers. 5 April 2018. New Scientist. https://www.newscientist.com/article/2165707-old-people-can-produce-as-many-new-brain-cells-as-teenagers/#ixzz6A1fPRp1J
5Columbia University News. Columbia University. News. Even Old Brains Can Make New Neurons, Study Finds: But new neurons in older brains may make fewer connections. 5 April 2018. https://www.cuimc.columbia.edu/news/even-old-brains-can-make-new-neurons-study-finds
6Moreno-Jiménez EP et al. Adult hippocampal neurogenesis is abundant in neurologically healthy subjects and drops sharply in patients with Alzheimer’s disease. Nature Medicine. 2019 Apr;25(4):554-560. https://www.ncbi.nlm.nih.gov/pubmed/30911133
7Lima SMA and Gomes-Leal W. Neurogenesis in the Hippocampus of Adult Humans: Controversy “Fixed” at Last. Neural Regeneration Research 2019; 14(11):1917-1918. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6676862/
8Underwood E. New Neurons for Life? Old People Can Still Make Fresh Brain Cells, Study Finds. Science. 25 March 2019. https://www.sciencemag.org/news/2019/03/new-neurons-life-old-people-can-still-make-fresh-brain-cells-study-finds
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