3.3 The Brain in Adolescence and Beyond

Research in the 1970s and 1980s revealed that the brain was not fully developed in adolescence. Huttenlocher studied the postmortem brains of individuals of different ages. He found that dramatic changes occurred related to puberty (Huttenlocher, 2002). During this time there is major growth in the frontal cortex in areas associated with executive functions such as planning and inhibition. This growth comes from the production of myelin as there is a decrease in synapses during puberty. The synaptic proliferation that occurred during the first year of life is refined. The synapses not in use are pruned, allowing the synapses that are used to become stronger and more efficient. The pruning within the frontal lobes does not occur until puberty, whereas it occurs earlier in other brain areas. Studies by Sowell and colleagues (1999) imaged the brains of children and adolescence. The images they obtained showed that the volume of brain matter shifted from childhood to adolescence in terms of an increase in white matter and decrease in grey matter into adolescence. The peak in grey matter density occurs at around age 12. We now know that the frontal lobes and associated white matter continue to mature even into the 20s.

As we note changes in the adolescent brain, we can also note corresponding changes in behavior. Adolescents show an increase in tasks of executive function, e.g., selective attention, planning, and problem solving. Additional studies have shown improvement in adolescence on tasks of inhibitory control and verbal fluency.

The brain does not stop changing at puberty. Proportions of grey matter decrease, with white matter increasing continues well into adulthood. As individual advance to middle age and old age, there is a slow decrease in the synapses. Experience continues to play a large role in the declining connections of the old brain.