Scientists have discovered that the brain’s center of reasoning is among the last areas to mature. The finding, by a team at the US National Institute of Mental Health, may help to explain why teenagers often seem to be so unreasonable. Researchers used imaging techniques to show “higher order” brain areas do not develop fully until young adulthood. The research is published in the journal Proceedings of the National Academy of Sciences.
The decade-long study used magnetic resonance imaging to follow the development of the brains of 13 healthy children every two years as they grew up. The aim was to get a better picture of how the brain develops so that it would be easy to pin down abnormalities that occur in conditions such as schizophrenia.
The researchers found that gray matter – the working tissue of the brain’s cortex – diminishes in a back-to-front wave over time.
They believe this is a key part of the maturation process, whereby unused and unneeded connections between brain cells are gradually destroyed.
They found the first areas to mature were those with the most basic functions, such as processing the senses and movement.
Next, came areas such as the parietal lobes, involved in spatial orientation and language.
Last to mature were areas such as the prefrontal cortex with more advanced functions such as integrating information from the senses and reasoning.
The sequence of maturation seen by the researchers in the developing brain roughly parallels the evolution of the brain from lower order mammals to the highly complex organ that is found in man.
For instance, the prefrontal cortex emerged late in evolution and is among the last to mature.
Researcher Dr. Judith Rapoport told BBC News Online: “Maturation starts with more basic facilities such as vision and hearing and then goes on to the ability to integrate and organize many inputs, to weigh consequences of behaviors and to relate to others.
“It is a smart sequence in terms of evolution and individual development.”