Do you know that some brain connections are not complete until your 20s?
The process is called myelination. It is the coating of neurons with a chemical insulator which makes a signal travel along it up to 100 times faster. There is signal regeneration at the nodes of Ranvier. The effect is similar to types of telecommunication transmissions.
Order of Occurrence
Myelination can be casually described as proceeding from the back collar up to the forehead (Fields, p 282, The Other Brain). The process continues from early infancy into young adulthood.
Vision (and sensory handling) occurs early. First you develop local categorization of objects, then (with myelinated axons) those results can be shared with other modules of the brain.
The effect of myelination is mastery of that particular cortical task and a ‘fixing’ of the manner in which people organize their reality.
The frontal cortex, areas which have executive function, finalize their myelination last. This occurs from one’s early 20s to late 20s. The executive functions control choosing long-term goals over immediate gratification. Until one can do that, they are still under control of their emotions and not reason.
One’s mental maturity, the age at which a person is able to integrate the full power of their thoughts, is reached more than a decade after puberty.
Biological Stages Tied to Knowledge Categorization. A non-technical discussion.
The Other Brain. About glia cells, which create the myelin which insulate the neural axon’s, among other tasks. Notes on R. Douglas Field’s book.
Limits of Working Memory. A critical feature of the frontal lobe. Notes on Torkel Klingberg’s book.