Scientists have shown for the first time that people over 70 can form new neurons just as well as their younger counterparts. This is a major discovery for neurogenesis, an area of research which has seen constant progress over recent years. Twenty years ago, it was thought we possessed a finite number of neurons and that it was impossible to form new ones throughout life...
The discovery that we continue to generate new brain cells marks a turning point in scientific understanding of cognitive function and ageing of the brain. It offers tremendous promise: is it possible to stimulate this surprisingly enduring ability, and if so, how? If this capability doesn’t decline as we get older, what does cause our mental capacity to age?
The authors of this study, published in the journal Cell Stem Cell, conducted autopsies on the hippocampi of 28 individuals aged 14-79 who had died suddenly. The hippocampus is a specific area of the brain involved in emotion, memory and learning. To prevent any errors in interpretation, the researchers ensured subjects had not been suffering from any cognitive disease.
They were surprised to note that in all cases, there was evidence of recent production of new neurons, at comparable levels, including among the oldest subjects. According to Maura Boldrini, Professor of Neurobiology and co-author of the study, “The elderly seem to be able to produce thousands of new neurons from progenitor cells, just like younger people”. Contrary to widespread belief, hippocampus volume appears to remain the same throughout life.
So what is it that causes brain function to decline in elderly people? The study’s authors did observe two key differences in the hippocampi of older subjects compared with younger ones: although there was an equal volume of new neurons, in the older subjects they were less vascularised and appeared to have difficulty in creating connections with other neurons. “It’s possible that neurogenesis maintains cognitive function throughout life in humans, but that certain psychological, emotional or traumatic factors contribute to its decline”, added Maura Boldrini.
A neuron is a specific brain cell which transmits, analyses and memorises information. It communicates with other neurons via fine threads of up to a metre long in the spinal cord.
A number of recent studies have demonstrated the importance of new neurons for accomplishing complex memory tasks. The discovery that the ability to form them continues as we age is therefore very good news.
However, neuron formation is one thing, but the ability of neurons to re-shape and re-organise themselves throughout life, as a result of individual experiences and environment, is another. This reconfiguring ability is called neuroplasticity.
And while there is a link between neuron numbers and the strength of cognitive function, neuroplasticity plays a major role in memory consolidation and information-processing. When one neuron repeatedly sends messages to another, the second neuron gradually becomes more sensitive to the first. In this way, powerful neuronal networks are formed as a function of our habitual behaviour and activities.
The bad news is that the researchers observed an age-related decline in this neuroplasticity.
Neurogenesis is the formation of new, functional neurons. It is most productive in the embryo during the first five months of pregnancy (culminating in reserves of 100 billion neurons), and continues at a lower but stable rate throughout life (1000-1400 new neurons each day). It is a fundamental stage in the formation of the body’s central nervous system.
New brain cells are formed from neural stem cells present in the hippocampus (or more precisely, in the dentate gyrus). These stem cells self-renew and are converted into different types of nerve cell, some giving rise to neurons. Before each conversion, they divide in such a way that stem cell populations maintain a certain consistency throughout life (1).
This conversion takes place in several stages:
Given that, surprisingly, neurogenesis appears to endure over time, it is neuroplasticity that needs to be stimulated, as well as vascularisation of neurons. It’s not just the number of neurons that’s important but the quality of the connections between them, the presence of cells that support them and the amount of blood vessels likely to adequately meet their needs in oxygen, glycogen and vitamins …
A number of studies have shown that neuroplasticity and neurogenesis can be improved in at least four different ways:
By continuing to fully engage in projects, cognitive and social activities (2-4)
Learning and mental exercises promote the survival phase of neurogenesis by stimulating integration of neurons into an existing circuit. What’s more, repetition of such activities (or increasing their difficulty or intensity) results in improved myelinisation of neuronal extensions which enables information to circulate more rapidly.
In other words, we produce the resources we need to successfully carry out learning processes and actions. If you learn to play a musical instrument at the age of 50, you’ll create new neurons and you’ll need to keep practising this activity over time if you want these neurons to combine into networks. If you want to maintain your memory ability, you need to continue memorising as much information as possible and keep learning new things. Conversely, if you abandon these activities, your body won’t bother to retain unnecessary neuronal circuits, still less recruit new ones.
While individual activities are important, it seems that those undertaken within a socially-rich framework produce even better results. Animal studies have shown spectacular improvements in neurogenesis when subjects were placed in an environment containing toys, partners and various objects that aroused their curiosity or desire to explore. If you feel as if your social life has diminished somewhat in recent years, you’d be well-advised to take urgent action to remedy the situation …
By increasing your intake of omega-3 and B vitamins (5-7)
Neurons generated in adults are small and need significant amounts of essential fatty acids, particularly omega-3 fatty acids, in order to build their demanding cell membranes. Omega-3 fatty acids are recognised by the scientific community and European authorities as helping to maintain cognitive function, particularly the natural-source fatty acid DHA (a high quality form of which is available in Super DHA from Supersmart).
Similarly, there’s no doubt that vitamins B2, B6 and B12 (combined in Coenzymated B Formula, a supplement formulated to provide B vitamins in their optimum forms) optimise the nervous system. Although adequate intake is essential for neurogenesis, deficiency is unfortunately becoming increasingly prevalent, especially in vitamin B12 (see: Is everyone lacking in vitamin B12? Why is there such widespread deficiency and what are the consequences?).
By increasing your levels of physical activity (8-9)
Physical activity increases the proliferation involved in neurogenesis. In particular, it improves blood volume in the brain which results in better cognitive performance, as demonstrated in animals and humans. Yet as this study clearly shows, vascularisation declines with age...
By improving your ability to de-stress (10-11)
Several studies have underlined the highly adverse effects of stress – whether physical or psychosocial - on cell proliferation and neurogenesis in general. It is therefore important to protect yourself against stress as much as possible, or failing that, to learn how to minimise its effects (through exercise, adaptogen plants, breathing techniques, etc.).
Key points to remember
Following this historic study, we now need to establish which endogenous factors are most significant in neurogenesis, particularly those where supplementation might improve the proliferation, survival and differentiation of neural progenitors. Research such as this would help the body to maintain normal neurogenesis, as well as to replicate as much as possible foetal neurogenesis where to 250,000 neurons per second are formed. Our wildest hopes may yet be realised...
(1) James B. Aimone, Yan Li, Star W. Lee, Gregory D. Clemenson, Wei Deng, and Fred H. Gage, Regulation and Function of Adult Neurogenesis: From Genes to Cognition, Physiol Rev. 2014 Oct;94(4):991-1026. doi: 10.1152/physrev.00004.2014.
(2) Peretto P, Schellino R, De Marchis S, Fasolo A. The interplay between reproductive social stimuli and adult olfactory bulb neurogenesis. Neural Plast. 2014;2014:497657. doi: 10.1155/2014/497657. Epub 2014 Jul 22.
(3) Oboti L, Savalli G, Giachino C, De Marchis S, Panzica GC, Fasolo A, Peretto P. Integration and sensory experience-dependent survival of newly-generated neurons in the accessory olfactory bulb of female mice. Eur J Neurosci. 2009 Feb;29(4):679-92. doi: 10.1111/j.1460-9568.2009.06614.x. Epub 2009 Feb 6.
(4) Opendak M, Briones BA, Gould E. Social behavior, hormones and adult neurogenesis. Front Neuroendocrinol. 2016 Apr;41:71-86. doi: 10.1016/j.yfrne.2016.02.002. Epub 2016 Mar 17.
(5) Hu X, Zhang F, Leak RK, Zhang W, Iwai M, Stetler RA, Dai Y, Zhao A, Gao Y, Chen J. Transgenic overproduction of omega-3 polyunsaturated fatty acids provides neuroprotection and enhances endogenous neurogenesis after stroke. Curr Mol Med. 2013 Nov;13(9):1465-73.
(6) Kang JX, Gleason ED. Omega-3 Fatty acids and hippocampal neurogenesis in depression. CNS Neurol Disord Drug Targets. 2013 Jun;12(4):460-5.
(7) Pu H, Jiang X, Wei Z, Hong D, Hassan S, Zhang W, Liu J, Meng H, Shi Y, Chen L, Chen J. Repetitive and Prolonged Omega-3 Fatty Acid Treatment After Traumatic Brain Injury Enhances Long-Term Tissue Restoration and Cognitive Recovery. Cell Transplant. 2017 Apr 13;26(4):555-569. doi: 10.3727/096368916X693842. Epub 2016 Nov 24.
(8) Yau SY, Gil-Mohapel J, Christie BR, So KF. Physical exercise-induced adult neurogenesis: a good strategy to prevent cognitive decline in neurodegenerative diseases? Biomed Res Int. 2014;2014:403120. doi: 10.1155/2014/403120. Epub 2014 Apr 9.
(9) Maass, A., Duzel, S., Goerke, M., Becke, A., Sobieray, U., Neumann, et al. (2015). Vascular hippocampal plasticity after aerobic exercise in older adults. Mol. Psychiatry 20, 585–593.
(10) Egeland M, Zunszain PA, Pariante CM. Molecular mechanisms in the regulation of adult neurogenesis during stress. Nat Rev Neurosci. 2015 Apr;16(4):189-200. doi: 10.1038/nrn3855.
(11) Lucassen PJ, Oomen CA, Naninck EF, Fitzsimons CP, van Dam AM, Czeh B, Korosi A. Regulation of Adult Neurogenesis and Plasticity by (Early) Stress, Glucocorticoids, and Inflammation. Cold Spring Harb Perspect Biol. 2015 Sep 1;7(9):a021303. doi: 10.1101/cshperspect.a021303.
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