There are more and more studies that associate cognitive improvements in our brain to the practice of exercise, especially aerobic. However, little is known as to why this occurs .
Key events in the evolutionary history of humans may have forged this link between exercise and brain function.
Hippocampus size
While it is possible to say that exercise increases the hippocampus , the memory-related region of the brain, it is not yet clear whether these effects in humans are related to neurogenesis or other forms of brain plasticity, such as increased brain cells. connections between existing neurons.
Researchers have also documented clear links between aerobic exercise and benefits for other parts of the brain, including expansion of the prefrontal cortex , a region that involves cognitive aspects such as planning, decision-making, or multitasking – skills that, like memory, tend to decline with aging or Alzheimer’s .
But why does exercise improve so many regions of our brain? Why does its natural deterioration slow down over time? What evolutionary advantage was there in the past for this to occur?
Two key events
According to David A. Raichlen , director of the evolutionary biology of exercise laboratory at the University of Southern California, and Gene E. Alexander , director of the brain imaging, behavior and aging laboratory at the University of Arizona, there were two key events to evolutionary level that link exercise with brain function.
Bipedalism : Going from walking on all fours to standing upright requires our brains to coordinate a great deal of information and, in the process, make adjustments to muscle activity throughout the body to maintain our balance. When coordinating these actions, we must also be vigilant for any environmental obstacles. In other words, unlike our quadruped ancestors, our brains began to be more cognitively challenged .
Hunting and gathering : the hominin way of life changed to incorporate higher levels of aerobic activity. Fossil evidence indicates that in the early stages of human evolution, our ancestors were probably relatively sedentary bipedal apes that ate primarily plants. Yet some two million years ago, as habitats dried up under cold weather, at least one group of ancient humans began feeding in a new way, hunting animals and gathering plant foods . Hunting and gathering involve much more aerobic activity than in other apes.
When searching for food far away, hunter-gatherers must survey their surroundings to make sure they know where they are. This type of spatial navigation relies on the hippocampus, the same region of the brain that benefits from exercise and which tends to atrophy as we age. In addition, they have to scan the landscape for signs of food, using sensory information from their visual and auditory systems. They must remember where they have been before and when certain types of food were available.
All of this is vital.
BDNF
When we engage in strenuous physical activity, our muscles begin to contract and relax, sending a series of chemicals to the brain, including a protein called IGF-1 . The brain interprets it as a moment of stress, as if we were fighting with an enemy or trying to flee from some danger. In response, it releases chemicals that protect nerve cells from damage, prompting them to grow, multiply, strengthen the connections between neurons and other nerve cells, and create new connections.
Of all these substances, the most important is brain-derived neurotrophic factor (BDNF). BDNF is essential during the formation of the nervous system because it promotes the plastic capacity of the brain so that it adapts better to situations and can be modified depending on the environment.
Although any animal in search of food must navigate and discover where to find food, hunter-gatherers have to perform these functions during brisk walks that can extend for more than 20 kilometers. At high speeds, multitasking becomes even more difficult and requires faster information processing .
From an evolutionary perspective, it would make sense to have a brain more capable of responding to a number of challenges during and after foraging to maximize the chances of food foraging success. But the physiological resources necessary to build and maintain such a brain, including those that support the birth and survival of new neurons, cost the body energy, which means that if we do not use this system regularly, we are likely to lose these benefits .
Currently, however, we do not need to participate in aerobic physical activities to find food to survive. We can simply go to the supermarket or call Glovo. These new sedentary habits cause brain atrophy. We simply needed a brain with certain highly developed brain regions to survive and reproduce; If we are no longer challenged to do so, those regions start to not be as important, and they lose steam as our muscles do .