Phase One of Brain Development
The first phase of brain development in babies is neurogenesis. During neurogenesis, new neurons are formed in the brain. Neurons are nerve cells that conduct electrical impulses throughout the body. In babies, more than 100 billion neurons are formed before birth, with as many as 50,000 neurons being formed every second during fetal brain development. These newly developed neurons allow the infant brain to link events to memories that occur at the same time. This is known as integration. This process continues after the baby is born into adulthood.
Phase Two of Brain Development
The second phase of brain development in babies is neural migration, also known as neuronal migration. In neural migration, the newly formed neurons in the brain are relocated to different areas of the brain dependant on their assigned function. Neural migration can occur in three different ways: radial neural migration, tangential neural migration or multipolar migration. This process begins while a baby is still in the womb and ends around its 10th month of life.
Phase Three of Brain Development
The third phase of brain development in babies is called myelination. Myelin is the coating that covers each neuron's axon, which is a long, arm-like fiber that protrudes from the neuron. Myelin forms a protective sheath around the neuron that keeps it from harm and allows it to be more effective in transmitting signals to other neurons. Myelination begins in the developing fetus and continues through a child’s teenage years.
Phase Four of Brain Development
Synaptogenesis is the fourth phase of brain development in babies. Synapses are the spaces where two neurons connect. When an infant is born, each neuron has 2,500 synapses, which totals 50 trillion synapses in the infant brain. By the age of 1, this number increases to 15,000 synapses per neuron for a total of 1,000 trillion synapses. Synaptogenesis is the formation of new synapses. When synapses are created to a high degree through new experiences, they allow the central nervous system to send and receive messages much more quickly between nerve cells. Like neurogenesis, synaptogenesis continues into adulthood.
Phase Five of Brain Development
Pruning is the fifth and final phase of brain development in babies. During this phase, neurons that have become weak or obsolete due to disuse are destroyed while those that have proven to be valuable through repeated use are strengthened and given room to expand. This is also known as neural plasticity. Which neurons are pruned is based on the child’s experiences and occurs most often between the ages of 3 and 16.