It was long ago thought that new neurons could not be generated in the brain. This was understood as a static and invariable entity that simply degenerated as we aged or due to brain injuries.
However, from the experiments of the biologist at the University of Berkeley (USA) Marian Diamond, it was shown in 1964 that the adult brain was plastic and adaptive. That study was a pioneer in identifying how the characteristics of the environment directly affected brain development and growth.
The experiment carried out had a large and spacious cage with twelve rats that grew in an enriched environment (elements to play or run on the spinning wheel, company, diverse feeding), as well as another twelve rats that were in a small cage, isolated, without social or play stimuli.
After eighty days, Diamond analyzed their brains and found that the cerebral cortex had been modified in the enriched environment group. In these, the cerebral cortex was more extensive, due to the growth of the dendritic spines of the neurons, angiogenesis was observed – a greater number of blood vessels -, the level of the neurotransmitter acetylcholine was increased, as well as that of the neurotransmitter derived from the brain , known by its acronym in English BDNF, a protein that is expressed especially in the cerebral cortex and the hippocampus, fundamental areas for processes such as learning and memory.
These data have generated countless studies aimed at analyzing the role of each of the elements that made up this enriched environment.
Neurogenesis and physical exercise
Since the pioneering studies of neuroplasticity, there have been multiple scientific evidences that demonstrate how factors such as diet, diverse cognitive activity, social environment, novelty and physical exercise are elements that indisputably favor this phenomenon.
Let’s focus on physical exercise.
The multiple benefits of regular physical exercise have been widely demonstrated in human and animal models. We know that it can contribute to neurogenesis, as well as play an important role in reversing and repairing existing neural damage, both in mammals and fish.
Understanding how this process occurs, and what factors set it in motion, can solve the puzzle to improve age-related memory loss and perhaps prevent neurodegenerative diseases, including Alzheimer’s.
The average brain contains about 100 billion brain cells, most of which were formed before birth. New brain cells continue to grow at an accelerated rate in early childhood. Over the years, neurogenesis gradually declines, but the process does not stop even during old age. Neurotrophic factors help stimulate and control this process, BDNF being the most important.
That’s especially true of the dentate gyrus of the hippocampus, even though there are other brain regions that also produce new brain cells.
Recently, a Harvard University research team, led by Rudolph Tanzi, has found that the hippocampus can produce between 700 and 1,500 new neurons every day. This may not seem like much when you consider the vast galaxy of neurons that we possess, but even this small number has value, as it keeps many existing neural connections active.
Thus, while most brains can develop new cells, the goal of science now is to find the best ways to do so. The idea would be that if the number of neurons can be increased even further through neurogenesis, the main function of the hippocampus could be intensified and the way in which people learn new information and access short and long-term memory could be enhanced. .
The results of this study support the link between exercise and neurogenesis.
It was found that aerobic exercise for eight weeks can double the rate of generation of new neurons in the hippocampus, in relation to those subjects who do not exercise.
In addition to producing BDNF, aerobic exercise may help increase liver production of an enzyme (Gpld1), which can also help with neurogenesis. We know that exercise accelerates the maturation of stem cells into fully functional adult cells and promotes the main existing cellular mechanism for learning and memory, called long-term learning. All of these elements are key to promoting learning and memory.
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Although these findings come from animal studies, people could get the same brain benefits from aerobic exercise. At this time, there is no substitute for regular exercise to help with neurogenesis.
However, it is not clear what type of aerobic exercise works best, nor how long and how long is sufficient. There is data suggesting a recommended 120-150 minutes of moderate intensity exercise per week.
Studies point to swimming as one of the most complete sports. It promotes a clear cognitive benefit (improvements in attentional processes, cognitive flexibility, memory) in both young and old people. However, any physical exercise that increases your heart rate, such as using a treadmill, biking, or vigorous walking, are ideal. The moving brain learns faster.