General brain development

Before birth and during early childhood, babies’ brains develop rapidly, as everything they experience is brand new. During this period, neural connections are formed and communication between different areas of the brain intensifies. Here’s a closer look at how a young brain develops.

A brain in the making

A child’s brain begins to form while they’re still in the womb, with several thousand neurons created every second. When a baby is born, their brain already has about 100 billion neurons—all the neurons they’ll ever need (and more!). They also have at least the same quantity of glial cells. These cells nourish and protect neurons so they can function properly.

At birth, most neurons have yet to form connections with one another. These connections, called synapses, are formed and strengthened in response to environmental stimuli and are essential for brain function.

The very first synapses form while baby is still in the womb: they start to hear sounds and voices, move, and feel the sensation of the amniotic fluid, and these stimuli promote the development of neural connections.

At birth, a newborn’s brain weighs about a quarter of what it will weigh once they reach adulthood. Their brain will double in size by the time they turn 1. By age 3, it will already be approximately 80% of its maximum size.

Every new milestone your child reaches and new skill they learn is a sign of this incredible growth. Smiling, babbling, holding a spoon, playing, walking—all these abilities are linked to brain development.

Neuroplasticity

Every time your little one learns something new, connections form in their brain. Billions of synapses are formed during infancy and early childhood.

While this is happening, other connections solidify, and still others are eliminated. The brain’s ability to “rewire” its own connections is called neuroplasticity.

The synapses that are used the most become stronger, and those that are faulty or unnecessary are eliminated. This phenomenon is called synaptic pruning. By getting rid of certain connections, the brain becomes more efficient.

The brain is at its most flexible, or “plastic,” during early childhood, when it’s developing rapidly. As a child grows and learns new things, their brain adapts to their experiences.

How environment impacts the brain

The brain’s ability to modify its connections has advantages, but it also carries some risk. Upsetting or traumatic experiences will affect a young child’s brain more than that of an older child. Likewise, when a young child is understimulated, fewer neural circuits are used and the brain doesn’t develop as well.

That’s why the first few years of life are so important for brain growth and why parents play such a big role. Whenever you care for your child, comfort them, give them affection, talk to them, or play with them, you’re helping their brain develop properly.

Nutrition is also important for brain development. Breast milk, for example, is rich in essential fatty acids that may promote healthy brain development, particularly in the first years of a child’s life. A number of studies have found that breastfed children perform better on intelligence tests. It’s thought that breast milk accelerates cognitive development. However, the beneficial effect seems to diminish over time.

Making sure your child gets a good night’s sleep is another way to promote brain development. When your child sleeps, their brain keeps working. The brain consolidates what it has learned by committing it to memory and continues to make connections between neurons.

When does a child’s brain stop growing? Science doesn’t have all the answers to this question yet. What we do know is that most areas of the brain reach maturity around the age of 25. After that, our brains continue to make and break connections, but more slowly than during early childhood.

The impact of stress on the brain

When a child experiences a stressful situation, such as thefirst day of daycare, a doctor’s appointment, or a sleepover away from home, their brain triggers the production of a stress hormone called cortisol. This hormone helps them adapt to the situation and cope better.

Normal, everyday stress is useful. But stress becomes harmful when it’s prolonged, frequent, and intense. This is called chronic or toxic stress. For instance, a child who is abused or who witnesses serious family conflicts may experience toxic stress.

The link between intense stress or adversity and brain development is complex and depends on many factors. However, a number of studies have shown that this type of stress is bad for a developing brain. A chronically stressed child may have a greater risk of developing mental health problems later on in life.

But there is hope, because young brains are highly adaptable! Care, affection, and strong relationships in early childhood can offset the negative effects of chronic stress.

These articles may also be of interest to you: (in French)

• Le développement du cerveau de 0 à 12 mois
• Le développement du cerveau de 1 à 3 ans
• Le développement du cerveau de 3 à 5 ans
• Le développement du cerveau après 5 ans

Things to keep in mind

• Most of the brain’s neural connections are made during early childhood.
• A child’s brain adapts and develops as they learn and have new experiences.
• The attention and affection you give your child, and the interactions you have with them, help their brain develop properly.

Scientific review: Miriam Beauchamp, full professor of neuropsychology, Université de Montréal, and researcher at CHU Sainte-Justine Research and copywriting: The Naître et grandir team Updated: April 2024

Photos : GettyImages/olesiabilkei et PeopleImages