3.1 How the brain develops
What we have learned about the process of brain development helps us understand more about the roles both genetics and the environment play in our development. It appears that genetics predispose us to develop in certain ways, but our experiences, including our interactions with other people, have a significant impact on how our predispositions are expressed. Research now shows that many capacities thought to be fixed at birth are actually dependent on a sequence of experiences combined with heredity. Both factors are essential for optimum development of the human brain (Shonkoff & Phillips, 2000).
Early brain development
The raw material of the brain is the nerve cell, called the neuron. During fetal development, neurons are created and migrate to form the various parts of the brain. As neurons migrate, they also differentiate, or specialise, to govern specific functions in the body in response to chemical signals (Perry, 2002). This process of development occurs sequentially from the ‘bottom up,’ that is, from areas of the brain controlling the most primitive functions of the body (e.g., heart rate, breathing) to the most sophisticated functions (e.g., complex thought) (Perry, 2000). The first areas of the brain to fully develop are the brainstem and midbrain; they govern the bodily functions necessary for life, called the autonomic functions. At birth, these lower portions of the nervous system are very well developed, whereas the higher regions (the limbic system and cerebral cortex) are still rather primitive. Higher function brain regions involved in regulating emotions, language, and abstract thought grow rapidly in the first three years of life (Zero to Three, 2012).
Brain development in childhood
Brain development or learning, is actually the process of creating, strengthening, and discarding connections among the neurons. These connections are called synapses. Synapses organise the brain by forming pathways that connect the parts of the brain governing everything we do—from breathing and sleeping to thinking and feeling. This is the essence of postnatal brain development, because at birth, very few synapses have been formed. The synapses present at birth are primarily those that govern our bodily functions such as heart rate, breathing, eating, and sleeping. The development of synapses occurs at an astounding rate during a child’s early years in response to that child’s experiences. At its peak, the cerebral cortex of a healthy toddler may create two million synapses per second (Zero to Three, 2012). By the time children are two years old, their brains have approximately 100 trillion synapses, many more than they will ever need. Based on the child’s experiences, some synapses are strengthened and remain intact, but many are gradually discarded. This process of synapse elimination—or pruning—is a normal part of development (Shonkoff & Phillips, 2000). By the time children reach adolescence, about half of their