What part of the brain does not reach full maturation until individuals are in their mid 20s?

The major reason that adolescents have different sensitivities to alcohol compared to adults is that their brains are still maturing. Although it was once thought that the brain is fully mature around birth this hypothesis has been disproven; now there is clear evidence that the brain does not mature fully until about age 24. One of the areas of the brain that matures late is the prefrontal cortex the area important in impulse control risk-taking behavior and judgment.

During development in the womb as many as 250,000 new neurons (the major cells in the brain) are created each day. These neurons use spatial and chemical cues to find their synaptic targets. By the time we are born our brains contain billions of neurons with trillions of connections. However the infant brain contains far more neurons than are present in the adult brain.

During the subsequent months and through adolescence careful pruning of neuronal connections eliminates all but the most “useful” connections between neurons. The result is a “thinning-out” process that selects for those neuronal connections strengthened through repeated experience. In this sense “cells that fire together wire together” while those that do not make meaningful contacts do not survive. In other words “use it or lose it”! These early pruning processes not only establish the neuronal networks to support learning throughout life but also allow the brain to be “sculpted” based on a person’s unique experiences.

Thus one might imagine how the presence of alcohol can interfere with this time-critical process of neuron pruning that forms the adult brain.

Figure 3.1 The brain undergoes maturation over the first 24 years of life; the sculpting and pruning of neurons and synapses is indicated by the decrease in gray matter (in red) in the cerebral cortex. (Courtesy of Gogtay et al. with permission). For an animated version click here.

The adolescent brain is not yet fully developed. As a result, alcohol can interfere with critical cellular events that help to form the adult brain.

Sean Locke Photography/Shutterstock.com

Your brain changes a lot between birth and adolescence. It grows in overall size, modifies the number of cells contained within, and transforms the degree of connectivity. The changes don’t stop once you turn 18. In fact, scientists now think your brain continues maturing and fine-tuning itself well into your 20s. So, when is a human brain finally done developing? And, with all the effort that it takes to build, what’s so special about the end result?

An adult brain differs from an adolescent brain in many ways. Between childhood and adulthood, the brain loses gray matter as excess neurons and synapses are pruned away. The rate of loss slows down by a person’s late 20s. At the same time, some brain regions strengthen their connections with each other, and the major nerve tracts become wrapped in insulating myelin, which increases the brain’s white matter. White matter volume peaks around age 40.

Much of the added white matter represents increased connections between widely separated brain areas. During childhood and adolescence, most brain networks are locally organized — areas near each other work together to accomplish a cognitive task. As we mature, distant areas of the brain begin linking up with each other, leading to larger and more widely distributed networks.

The most important brain area to become fully “wired up” in adulthood is the prefrontal cortex — the front portion of the frontal lobe. This area handles many of our higher-level cognitive abilities such as planning, solving problems, and making decisions. It is also important for cognitive control — the ability to suppress impulses in favor of more appropriate actions. The adult brain is better wired for cognitive control compared to the adolescent brain, which is more influenced by emotions, rewards, and social acceptance when it comes to making decisions.

Intelligence also peaks during early to middle adulthood, roughly ages 25 to 60. However, intelligence involves many different cognitive abilities, each of which develops on its own timescale. Fluid intelligence, which includes abilities like solving problems and identifying patterns, peaks around age 30. By contrast, crystallized intelligence, which deals with vocabulary and knowledge of facts, increases until about age 50.

While the adult brain is more cognitively capable than the teen brain, there might not be a single point in adulthood at which all (or even most) of our cognitive functions operate at peak performance.

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This article was adapted from the 8th edition of

Brain Facts.

About the Author

Alexis Wnuk

Alexis is the science writer and editor for BrainFacts.org. She graduated from the University of Pittsburgh in 2012 with degrees in neuroscience and English.

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What part of the brain does not fully developed until mid 20s?

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