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Brain Development in Children – The Early Years

Neuroscience research has shown us that early childhood is a time of tremendous brain development. The young brain literally changes shape and size in response to everything encountered in the early years of life. New environment, life experiences, caretakers and relationships can all affect the way a child’s brain circuits are wired.

Find out how to help your child’s brain develop optimally.

Brain diagram with five different colors on different regions - early brain development and how many billions of neurons by age 2

Brain Development in Children

How Many Brain Cells Does a Child Have

A baby is born with roughly 86 billion neurons​1​, almost all the neurons the human brain will ever have​2​.

Although a newborn has about the same number of neurons as an adult, it has only 25% of its adult brain volume.

That’s because infant’s neurons are connected by only some 50 trillion neural connections, called synapses, whereas a grownup has about 500 trillion of them​3​.

This network of synaptic connections will ultimately determine how a child thinks and acts.

What Is Synaptic Pruning in Early Brain Development

Synaptic pruning is the process in which unused neurons and neural connections are eliminated to increase efficiency in neuronal transmissions.

The network of synapses grows rapidly during the first year and continues to do so during toddlerhood. The brain development in toddlers is fast.

By age 3, the synaptic connections have grown to 1000 trillion.

But not all of the synapses will remain as the child’s brain grows.

Life experience will activate certain neurons, create new neural connections among them and strengthen existing connections, called myelination.

Unused connections will eventually be eliminated. This is called synaptic pruning​4​.

Synaptic pruning is the process in which unused neurons and neural connections are eliminated to increase efficiency in neuronal transmissions.

Building massive connections, creating and strengthening them through life experiences and pruning unused ones is a remarkable characteristic of human brains.

This experience-based plasticity allows babies to adapt flexibly to any environment they’re born into without the constraint of too many hardwired neural connections​5​.

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A network of neuron synapses brain architecture - where synaptic pruning happens

The Use It Or Lose It Brain Sculpting Property

The benefits of developing a baby’s brain this way are enormous, but so are the costs and the risks​6​.

First, children require a lot of care, i.e. life experiences, before they can be independent.

Second, what parents do or don’t do during the formative years can have a profound impact on the child’s mental health and life.

Here’s a synaptic pruning example. Let’s say a parent consistently shows a toddler love and care, then the “love-and-care connections” will develop or strengthen over time. But if the parent constantly punishes or is harsh to the child, then the “punitive-and-harsh connections” will be stronger instead. And because the love-and-care experience is missing, those corresponding brain cells will wither and eventually be removed from the child’s brain circuits. As a result, the child grows up lacking the love-and-care understanding that is essential to create healthy, meaningful relationships in his future life​7​.

Why The Early Years Matter in Baby Brain Development

Early years of life is a period of unique sensitivity during which experience bestows enduring effects​8​.

Although this experience-based brain plasticity is present throughout one’s life, a child’s brain is a lot more plastic than a mature one.

Brain cell pruning also occurs most rapidly during a child’s preschool years.

The density of these connections during adulthood will reduce to half of that in a toddler at age two.

This is why nurturing and positive parenting are so important.

Things can go seriously wrong for children deprived of basic social and emotional nurturing.

Critical Periods and Sensitive Periods in the Developing Brain

Within early childhood, there are also windows of time when different regions of the developing brain become relatively more sensitive to life experiences.

These periods of time are called critical periods or sensitive periods.

During a critical period, synaptic connections in those brain regions are more plastic and malleable. Connections are formed or strengthened given the appropriate childhood experiences. After the critical period has passed, the synapses become stabilized and a lot less plastic.

For example, a young child can learn a new language and attain proficiency more easily before puberty. So the sensitive period for language skills mastery is from birth to before puberty.

Another example is emotional regulation. Emotional self-regulation forms the foundation of the brain architecture. It’s a person’s ability to monitor and regulate emotions.

Emotion regulation is not a skill we’re born with. Yet it’s an essential skill in a child’s healthy development​9​.

The sensitive period of learning this crucial life skill is before a child turns two. Critical or sensitive period is another reason why early life experiences matter so much.

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Nature vs Nurture In Child Development

Besides influencing how the network of brain cells is formed, early life experience potentially has another significant impact on a child’s life.

A large amount of scientific evidence indicates that life experience can affect gene expression — how information in a gene is used (epigenetics) — in some cases by slowing or shutting the genes off, and in others by increasing their output​10​.

This is why identical twins are not carbon copies of each other.

Although their genes (DNA code) are identical, their epigenetic markers are different from birth and continue to diverge as they interact with the environment in distinctive ways.

Even more important, these epigenetic changes can be permanent and passed down from generation to generation.

In the age-old nature-versus-nurture debate, epigenetics offers a surprising middle ground.

Genes are profoundly important, but so are environmental factors.

Also See: Benefits of Sensory Play to Brain Development

When Does a Fetus Develop a Healthy Brain

Neuron production in the fetus begins in week 3 post-conception during the embryonic period.

As neurons are produced, they migrate to different brain areas to form rudimentary structures of the developing brain, central nervous system, and peripheral nervous system.

This is a period of rapid neurological development and brain growth to create cortical and subcortical structures.

brain in tree shape with leaves in the middle - When does the brain stop developing

When Does Your Brain Stop Developing

So, at what age is a child’s brain fully developed?

On average, the brain is fully developed by age 25. Although an individual’s brain growth trajectory can vary slightly, most people’s brain development is complete in their mid-20s.

However, it doesn’t mean the brain stops changing.

The interconnections in our brains keep changing throughout our lives, but as we age, they do so at a much slower rate.

The Importance Of Child Brain Development In Early Childhood

Neuroplasticity and epigenesis are two major cornerstones in understanding a child’s neurological and brain development in early years.

While we don’t need to be perfect parents (and who can be?), good enough parenting can do a child tremendous good.

In particular, among the different parenting stylesauthoritative parenting is the best parenting style associated with the best outcome while other types of parenting styles can lead to a devastating consequence.

Early childhood education is also important to a child’s cognitive growth. Attending a quality preschool has been shown to benefit kids’ development in the long term.


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    Azevedo FAC, Carvalho LRB, Grinberg LT, et al. Equal numbers of neuronal and nonneuronal cells make the human brain an isometrically scaled-up primate brain. J Comp Neurol. Published online April 10, 2009:532-541. doi:10.1002/cne.21974
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    Graham J. Children and Brain Development: What We Know About How Children Learn. Cooperative Extension Publications.
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    Gauvain M, Cole M. Readings on the Development of Children. 5th ed. Worth Publishers; 2008.
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    Tau GZ, Peterson BS. Normal Development of Brain Circuits. Neuropsychopharmacol. Published online September 30, 2009:147-168. doi:10.1038/npp.2009.115
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    Huttenlocher P. Synapse elimination and plasticity in developing human cerebral cortex. Am J Ment Defic. 1984;88(5):488-496.
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    Tottenham N. The Importance of Early Experiences for Neuro-Affective Development. In: The Neurobiology of Childhood. Springer Berlin Heidelberg; 2013:109-129. doi:10.1007/978-3-662-45758-0_254
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    Wright MO, Crawford E, Del Castillo D. Childhood emotional maltreatment and later psychological distress among college students: The mediating role of maladaptive schemas. Child Abuse & Neglect. Published online January 2009:59-68. doi:10.1016/j.chiabu.2008.12.007
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    Balbernie R. Circuits and circumstances: the neurobiological consequences of early relationship experiences and how they shape later behaviour. Journal of Child Psychotherapy. Published online January 2001:237-255. doi:10.1080/00754170110087531
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    Chen Y, Baram TZ. Toward Understanding How Early-Life Stress Reprograms Cognitive and Emotional Brain Networks. Neuropsychopharmacol. Published online June 24, 2015:197-206. doi:10.1038/npp.2015.181
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    Stiles J, Jernigan TL. The Basics of Brain Development. Neuropsychol Rev. Published online November 3, 2010:327-348. doi:10.1007/s11065-010-9148-4

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* All information on is for educational purposes only. Parenting For Brain does not provide medical advice. If you suspect medical problems or need professional advice, please consult a physician. *