Periods of brain growth and development
Whilst the evolution of the structures of the brain has happened over millions of years, an individual’s brain develops over a lifetime of about 85 years. There are three stages of particularly rapid brain growth and development during this time. The first stage is the time spent in the womb, when we develop from the joining of two cells at fertilization, to a very complex living organism at birth 9 months later. The second rapid stage of brain growth and development occurs during the first 3 years of life. The third stage of significant brain development occurs during our adolescent years. The brain, however, continues to develop throughout life.
The brain continues to mature during our ‘adult years’. All activities become much easier with practice. This is reflected in the degree of activity measurable in the brain. Many areas of the brain are seen to ‘light up’ on neuroimaging when we attempt something new. With practice, the areas and neural networks in the brain that are activated to achieve the same result become more defined and refined. Sometimes, as when motor movement and activity are involved, the necessary brain functioning takes place mostly in non-cortical brain areas such as areas in the brainstem and cerebellum. When some ‘higher executive functioning’ uses areas of the prefrontal cortex (PFC) to achieve a desired result, the area of the PFC used by adults is smaller to achieve the same result than that used by adolescents. Brain functioning becomes more efficient with practice.
Throughout adult life, a small region of the hippocampus, the dentate gyrus, continues to generate new differentiated nerve cells from stem cells. Antidepressants may exert their effects on behavior, in part, by stimulating the production of neurons in the hippocampus.