It was recently discovered that, contrary to what was thought, the adult brain continues to manufacture neurons in the hippocampus, a brain region related to learning and memory, until the death of the individual. What is not yet known exactly is how and why these new nerve cells are born.
An article that has just been published in the journal Trends in Cognitive Sciences reviews the latest research in this regard, carried out with laboratory mice. “New neurons can fine-tune the hippocampus to changes in the environment,” summarized Maya Opendak of Princeton University and co-author of the report.
What is becoming increasingly clear is that stressful experiences, such as lack of sleep, social rejection, or exposure to the odors of predators, slow the growth of nerve cells in the mammalian brain. And on the contrary, pleasant experiences, such as mating or physical exercise, stimulate neurogenesis. In the first case, individuals come to manifest cognitive disorders, such as difficulties in remembering or learning to move through different environments.
On the other hand, scientists still disagree on the rate of production of new neurons : are they born only under specific circumstances or are they continually manufactured in case they are needed in the future?
Another tricky issue is its adaptive function. In fact, the stress brake on neurogenesis increases survival options, since exploratory behavior is inhibited for the sake of the individual’s safety. On the other hand, the increase in the number of nerve cells due to gratification would reduce anxiety and improve the capacity for learning and exploration, essential factors to achieve reproductive success. However, when the levels of emotional tension are too high and continuous, a counterproductive response occurs: the “stop” of the neuron factory can produce anxiety disorders and depression.
Another finding from the experiments is that mice with higher social status produce more nerve cells than subordinates, which can be extrapolated to social relationships between humans.
