By the age of three, a child’s brain has reached almost 90 percent of its adult size. During those first three years, higher functioning brain regions, like the limbic system and cerebral cortex, grow rapidly. These regions are crucial to child development because they regulate emotions, language, and abstract thought. To reach full potential, these regions largely depend on receiving stimulation, which triggers activity and provides the foundation for learning.
If this stimulation is lacking or absent, for example if a child’s caretaker is inattentive, hostile, depressed, or cognitively impaired, the child’s brain could be damaged. Because the brain is malleable, it will adapt to a negative environment just as easily as it will adapt to a positive one.
Brain development is the process of creating, strengthening, and discarding connections between neurons, the building blocks of the brain. These connections are called synapses, which are essentially junctions of nerve impulses on the super highway of consciousness. At its peak, the cerebral cortex of a healthy toddler creates two million synapses per second. By the age of two, a child’s brain has approximately 100 trillion synapses.
Based on the child’s experience, certain synapses are strengthened and remain intact, while non-essential synapses are shed in a natural elimination process called pruning. For example, an infant’s brain makes connections to hear language. Over time, synapses that correlate to parental voices will strengthen, while synapses that correspond to a stranger’s voice will weaken and be discarded.
For children who experience trauma, their brains are at risk of pruning vital synapses that should remain intact. For example, infants are genetically predisposed to form strong attachments to their primary caregivers. But if the caregiver is neglectful, that durable bond might be severed, or pruned. This broken connection can have ripple effects on into adolescence and beyond, perhaps contributing to a young person who finds it difficult establishing trust with adults.
When a child’s environment is filled with domestic violence, physical abuse, chaos and other catalysts of toxic stress, their brains may become hyper-alert for danger or not fully develop. As their neuronal pathways strengthen to cope under these negative conditions, they may struggle to respond to a kind and nurturing environment.