Brain Development in Infants and Toddlers

Once infants enter the world, their brain is bombarded with information that fuels neural growth. During the first three years of life, cells proliferate, differentiate, and migrate at an incredible rate! As they arrive in their permanent network, they build connections with neighboring cells, and synaptogenesis occurs at each junction. Synaptogenesis is the building of connections between the end of one axon and the receptor of a neighboring dendrite. It is an essential part of cell growth, and as new cells proliferate and migrate into place, they are quick to find neighbors to connect with.

Well into toddlerhood, neural cell proliferation continues to happen quickly and abundantly. Every experience for an infant or toddler is new, and therefore the brain chooses to use nearly all of them to build new network connections. It cannot be sure what will and what will not turn out to be important. Around age 3, the brain is as dense with neurons and neural connections as it will ever be throughout the lifespan! Creating a strong connection at a synaptic juncture is important to the lifespan of a neuron. Neurons that make weak or no connections cannot transfer impulses efficiently and tend to be removed in a process called pruning.

But this density is hard to sustain, both in terms of keeping connections accessible and in terms of fueling the brain with nutrients and oxygen. Therefore, the brain needs to start disconnecting some of these neurons. This process is called pruning, because it is similar to what a gardener might do with a plant – carefully removing selected neurons in an effort to ensure better health for the most important ones. Pruning of neural networks continues throughout childhood and adolescence with different areas of the brain experiencing greater intensity of pruning at different times (Courage & Howe, 2002).

In upcoming chapters, you will read more about the experiences that infants and toddlers have which help to support their brain development. As you learn about those important stages of childhood, keep in mind what is happening behind the scenes in each child’s brain!