It is necessary to circumcise the brain

What is the purpose of brain remodeling during puberty?

Questioner: Martha M. from Cologne via email

Published: 11/08/2014

We actually already have a well-functioning brain, which is then completely rebuilt again during puberty. What is the biological point of this extensive renovation work?

The answer from the editors is:

Answer from Kerstin Konrad, Professor for Clinical Neuropsychology of Children and Adolescents at RWTH Aachen University:

During adolescence - the phase from late childhood to adulthood - two types of remodeling processes take place: one in the gray matter and one in the white matter. With so-called synaptic pruning, superfluous nerve connections are cut again. This affects the gray matter, which is made up of nerve cell bodies and synaptic contacts, among other things. This breakdown of the superfluous nerve connections takes place depending on experience. The “use it or lose it” principle prevails: the connections that are rarely used and thus superfluous are broken down. The nerve connections that are often used, on the other hand, are strengthened. This enables individual nerve networks to work more efficiently. We find this phenomenon in other mammals as well.

Possibly the biological purpose behind it is to allow the brain the greatest possible plasticity, the best possible adaptability. This plasticity has a protective function: If, for example, an injury to the brain leads to a loss of nerve connections, the loss can be compensated for with the other, numerous existing contacts. The plasticity also helps with learning: when a child acquires the mother tongue, it is first necessary and sensible that there are many nerve connections. Many different areas of the brain are involved in language acquisition. If you later master your native language, it is more efficient if you only use a small, narrowly defined network with few synaptic connections. When “cutting to size” synaptic contacts, the main aim is to establish neural networks that are small and efficient.

With us humans, the remodeling processes last a very long time and continue even after reaching sexual maturity; this is not the case with other animals. The biological meaning behind this is probably that people can acquire skills such as a second language even after puberty. The evolutionary advantage of the long-lasting remodeling processes is therefore probably an increased plasticity and the associated higher learning potential. Adolescence is a phase in which new experiences play an important role. And the plasticity of the brain enables optimal adaptation to the environment through new experiences.

The second type of remodeling process during adolescence involves white matter. It consists of long nerve fibers. Unlike gray matter, it doesn't increase and then decrease. Instead, it increases steadily between childhood and adult life. The cause is that nerve fibers are coated with fatty myelin. This isolates the nerve fibers, much like a power cable is isolated from a plastic sheath. This means that nerve impulses can be passed on more quickly. In this way, distant areas of the brain can communicate with one another faster and better.

This maturation process - presumably strongly hereditary - leads to the fact that the information processing of young people becomes as fast as that of adults.

Answer recorded by Christian Wolf