Teen years are definitely tough and scientists, who have tracked the physical changes that take place in the teen brain, with magnetic resonance imaging (MRI) technology conducted over a child's life, can prove it. Genes and environment play a role in brain development but the teen brain studies have found that brain development seems to follow a "use it or lose it" process. Researchers have also discovered that brain growth occurs throughout the teen years rather than just in early childhood.
Pruning Pathways
Brain development follows a flow and ebb process. Brain cells and synapses proliferate and then are pruned back. By pruning unused pathways, the brain strengthens the pathways that are relevant and used. White matter is the way the brain prunes pathways. Important brain pathways become insulated and wrapped with a myelin sheath, which stabilizes and strengthens that pathway just as insulation on electrical wires improves conductivity. The brain cells are what constitute grey matter. Myelin sheathing is what scientists refer to when they talk about white matter. Before the long-term MRI studies, at the National Institute of Mental Health (NIMH) in 1999, scientists thought that brain structure was laid down by the time a child turned 5 or 6, when 95 percent of the brain is formed.
Prefrontal Cortex
Babies go through a booming phase of brain cell and synapse proliferation. The pruning phase begins around age 3. Now scientists see that a second wave of growth occurs around age 11 or 12 and a second pruning phase occurs in adolescence. NIMH scientists Jay Giedd and Judith Rapoport, along with their colleagues at McGill University, discovered the second surge of synapse formation, just before puberty, in the prefrontal cortex region of the brain. The prefrontal cortex is the seat of executive function: impulse control, judgment, planning and reasoning. This "CEO" of the brain is involved in modulating mood, organizing and making use of working memory. The teen brain loses gray matter between ages 13 and 18 but white matter increases.
Corpus Callosum
Jay Giedd took part in another study with Paul Thompson of UCLA and the McGill researchers. This study looked at physical changes in the corpus callosum, the bridge that connects the left and right sides of the brain. The corpus callosum is involved with language acquisition and associative thinking. The scientists discovered that growth in this area occurred before and during puberty, confirming the idea that the ability to learn new languages decreases after age 12 and highlighting another physical change in the teen brain. Corpus callosum MRI studies form part of a larger twins' study. Corpus callosi are very similar in twins while the cerebellum area of the brain is not. The scientists believe that the cerebellum is more susceptible to the environment. At the time of publication, the twins' study is hoping to shed light on the nature versus nurture idea in terms of child brain development.
Youths' White Matter
UCLA scientists compared MRI scans of adults aged 23 to 30 with those of teen brains. They found much more myelin, or white matter, in the adults, especially in the frontal cortex. According to the National Institute of Mental Health, this can explain why your teen, with less myelin, may exhibit poor judgment, planning and organizational skills. White matter in the parietal and temporal lobes seems to mature in the teen brain and remain relatively stable. These brain regions are involved in auditory, language, sensory and spatial functions.
Cerebellum
The cerebellum may also help with the development of physical coordination and the MRI studies have revealed that this brain region is also involved in processing mental tasks. The cerebellum improves mental activities such as higher thought and philosophy, mathematics and music, decision-making and social skills. The cerebellum develops throughout the adolescent and teen years.
