The birth of New neurons In our brain it is a finely regulated process by factors that can be internal (endogenous), made up of ours genetic heritage and come on hormonesand external (exogenous) factors, like ours lifestyle el ‘diet. In the human being, this phenomenon, called neurogenesistakes place massively during the prenatal development and in subsequent period immediatelywhen the precursors of neural cells proliferate and differ in giving shape to brain structures. In age adultneurogenesis continues in specific brain areas, although at a very reduced rate compared to the age of childhood.
Genetics
As it is easy to guess, a fundamental role is played by ours genetic heritage. Depending on the instructions written in our genes, the proliferation and the differentiation neural cells can be more or less effective. Let’s imagine the brain like a great garden where neurons constitute the plant. Neurogenesis is the process of cultivation and growth of these plants, from sowing to complete growth. In this metaphor, our genes contain the instructions To cultivate these plants, that is, the neurons, starting from the seeds (the neuronal stem cells). This manual contains several “chapters” (in technical jargon, signaling routes) which indicate when and how to grow new “plants” in our brain garden:
- Via Notch: it is the reporting route that “brakes” growthkeeping some “waiting” cells and keeping them for future uses. If this brake breaks, all the cells will grow simultaneously and then you will no longer have seeds for the future.
- Vie WNT and FGF: are streets that they stimulate growth acting like fertilizers. Their activation increases the production of new neurons, as after a stroke, when the brain tries to repair the damage by activating the “fertilizer” WNT.
Sometimes, of “printing errors“(mutations) in the genetic manual can lead to planting too many seeds at the beginning (leading to pathologies such as microcephaly) or not producing enough plants-neurons, or even growing in the wrong places creating an disorganized” garden “. Furthermore, some people have”editions” different of the instruction manual, namely the genetic variants: for example, a genetic variant (called in technical jargon “variant BDNF VAL66MET) leads to the reduction of nourishment available for the new neurons. The carriers of this variant tend to have a hippocampus (the central of memory) smallerwith possible slight memory problems and greater risk of mood disorder.
Hormones
In our metaphor of the “brain-yellow”, the hormones they could be seen as the system of irrigation and fertilization that determines if the neurons will grow lush or wandering. Sex hormones such as estrogen They act as fertilizers, multiplying stem cells and supporting neurogenesis. Also the testosteronestimulates the growth of new neurons, but in excessive doses it becomes harmful, increasing cell degeneration. The progesterone It acts as a protector, especially after damage given by brain injuries, helping repair.
The stress hormone (the cortisol) instead acts as a herbicker and, if present in very high concentrations for too long, drastically reduces the birth of neurons, especially in the hippocampus, fundamental for learning. Finally, also the thyroid hormones They are fundamental during pregnancy for brain development, and in adults they support the functionality of neurons. With age, these “brain irrigation systems” deteriorate physiologically: stem cells become less active, the “good hormones” decrease while the degenerative factors increase and which inhibit the production of new neurons.
Environment and lifestyle
Our brain, like any ecosystem, is also strongly influenced by environmental factors, that is, everything around us. Even before being born, what a mother eats, breathes or consumes during pregnancy It can determine the fate of the child’s neurons. In the adult, it chronic stress It is like a “poison” for new neurons, while living in stimulating environments And rich in novelties it works as a “fertilizer” for neural growth. Also thediet He plays a crucial role: a hypercaloric diet usually negatively affects adult neurogenesis, while low -calorie diets (always in adulthood) seem to favor it. Even the microbiota, communicating with the brain influences neurogenesis. Other physical factors such as cranial trauma, radiation or infections may temporarily Stimulate or, more often, damage the brain’s ability to produce new neurons.
Ours too daily habits They are powerful neurogenesis modulators. THE’aerobic exercise It is perhaps the largest “ally” of neuron production: running regularly drastically increases neurons in the hippocampus improving memory and mood, so much so that even in elderly people a physical activity program can increase the volume of the hippocampus by 2%. THE’active learningThen, it is essential: to learn new skills or solve complex problems helps newly born neurons to survive. On the contrary, the sleep deprivation It is an enemy of neurogenesis: a good regular sleep is a cure -all for the birth of new neural fabric.
Also some drugs of which we use can directly influence neurogenesis. The antidepressants Serotonin Ricapation inhibitors (SSRI) stimulate the birth of new neurons in the hippocampus, so much so that part of their therapeutic effect seems to depend on this mechanism. Lithium (used for bipolar disorder) also significantly increases neurogenesis. On the other hand, many drugs chemotherapy And radiation They seriously damage stem cells (future neurons), causing cognitive problems. The abuse of drugs It generally has negative effects: alcohol and opiates, experienced in the rats, have it reduced neurogenesis even by 42%.
