A human baby is born with a staggering amount of neurons — somewhere around 100 billion — but they’re not connected yet.

Like all mammals, our brains come “assembly required” — like a Lego super deluxe building set. Zillions of itty biddy pieces are there, and the possibilities are exciting and endless, but it’s going to take a heckuva lot of time to put it together.

As little people grow, interact with others, and explore the world, connections are wired in their brains based on their experiences. Life sculpts their brains by way of electrical impulses. This ability of the brain to change form and function based on incoming stimuli is called neuroplasticity.

Over the years as you behave, feel, and think repeatedly in the same ways, the default pathways in your brain become efficient and entrenched. In youth, your brain creates new circuits effortlessly. As an adult, new connections and patterns can be made throughout your life, but it requires much more effort. (That’s why habits are so darn hard to break!)

Understanding how your brain works and how experience alters it can help you intentionally remodel your circuits, change your behavior, and positively impact your life. In her book, Habits Of A Happy Brain, Loretta Graziano Breuning, PhD, explains how experience physically alters your brain.

Experience Insulates Young Neurons

As a neuron gets used more often, it develops a fatty coating called myelin. Myelin helps neurons conduct electricity more efficiently. Much of your myelin is produced by the age of two, tapers off around seven, and ramps up again at puberty. Bruening writes:

Anything you do repeatedly in your ‘myelin years’ develops huge, efficient branches in your neural network. This is why child prodigies exist, and why little kids on ski slopes whoosh past you even though you’re trying much harder than them. This is why new languages are hard to learn after puberty…That’s because your new vocabulary is just skinny ungreased circuits. Your thoughts are generated by big myelinated circuits, so the electricity has trouble finding a place to flow.

Experience Makes A Synapse Efficient

A synapse is the space between two neurons. An electrical signal can only jump the gap between neurons to keep moving in your brain if it has enough oomph when it reaches a synapse. These synapse breaks help your brain filter out important input from noise.  Anything deemed not worthy stops, and info tagged significant keeps going.

What’s required for a signal to make it across a synapse is pretty complicated. Dr. Bruening explains it like this:

It’s as if the tip of each neuron has a fleet of rowboats ready to ferry the electrical spark across the synapse to specially fitted docks on the next neuron. These rowboats get better at crossing over to their docks each time they’re set into motion, and that’s why experience improves the chances of a synapse firing. 

A synapse develops in two ways: repetition and emotion. Repetition happens gradually. Emotion develops a synapse instantly.

• Repetition develops a synapse gradually. If a synapse is activated enough times, it learns to carry signals efficiently – even without extra rowboats.
• Emotion develops a synapse instantly. In your brain, emotions are chemical molecules that can change a synapse immediately and permanently. Whatever felt good or bad in your past stationed more rowboats at synapses which will fire more easily in the future.

Only Neurons That Are Used Stick Around

Like we learned earlier, the human brain has billions of neurons at birth. Neurons that aren’t used begin to wither in a process called synaptic pruning. Pruning actually increases intelligence and helps a child stay focused and alert instead of attending to every little thing in their environment.

Most pruning takes place between the ages of two and seven. Because of this, a child’s brain link’s new experiences later to relevant past experience instead of storing each new experience as an isolated chunk. According to Dr. Bruening:

Richly interconnected networks are the source of our intelligence, and we create them by building new branches onto old trunks instead of building new trunks. So, by the time you are seven, you are really good at seeing what you have already seen and hearing what you have already heard.

New Synapses Grow Between Neurons You Use

Each neuron has multiple synapses on its many branches or dendrites. Electrical stimulation causes new dendrites to grow. As more dendrites grow in hubs of electrical activity, impulses are going to jump the gaps from one dendrite to another and new synapses are born. When the brain forms memories or learns a new task, it encodes the new information by tuning the connections between neurons. This is how your brain links ideas, thoughts, or concepts.

Emotion Receptors Grow Or Atrophy

For electricity to cross a synapse, the dendrite on one side must release a chemical that arrives at a receptor on the other side. Each of our brain chemicals has a complex shape that fits its own special receptors the way a key fits a lock. When you feel flooded with emotion you are releasing more chemicals than those receptors can process.

Think of the implications of this in your life. A neuron fires because a happy chemical key has opened a receptor lock, which makes it more likely to fire in the future. In other words, you have to use your happy receptors or lose them.

You Are Not A Slave To Your Synapses

I think it’s important to make a final note here.

Your brain is incredibly efficient and will take the path of least resistance every time if left to own devices. BUT …

You don’t always have to act on your neurochemical impulses because your prefrontal cortex, your thinking brain, can interrupt and inhibit a response. Your thinking brain can divert your attention from a brain circuit instinctively activated by the outside world to one you intentionally activate internally. This allows you to observe your gut reactions and then consciously decide how to respond rather than react.

Mindfulness, meditation, thought reframing, and visualization can help you strengthen your mental muscles to do this. Inserting conscious will is the power you have to change your brain and life.