Neural Development in Adolescence

The development of the central nervous system involves several stages of maturation according to age. Several authors asserted that although human beings are born with a huge number of neurons approximately half of them are lost within the two first years of life. The rationale underlying this process is that the brain does not need an excessive number of nerve cells but need to amplify the already existing connections, increasing the number of synapses. In other words, during the course of development, the nervous system prioritizes qualitative aspects (improved transmission among and integration of neurons via synapses) over quantitative aspects (a large number of neurons with rather isolated actions). Recently, Brazilian researchers elaborated new techniques to count neurons and found that their number is approximately 86 billion in healthy human beings. In certain brain areas, neurogenesis continues throughout life, particularly in the case of the hippocampus, a memory and learning critical area. That process is exacerbated during adolescence. Some authors have found higher levels of hippocampal neurogenesis in adolescent mice than in adults. In addition, this process seems to be highly sensitive to the action of drugs, such as alcohol.