Understanding the Youngest Minds

Human Neuronal Development Between Birth (left) and Age 2 (right)

I became convinced of the vital importance of early childhood when I was a 21 year old medical student. An instructor in my neuroanatomy class lent me a set of microscope slides that after 60 years still blow me away.

I’ve reproduced two of them here. They are from exactly the same part of the brain, but taken at two different ages: birth and two years of age.

These are NOT diagrams or schematics. They are magnified photos of actual brain tissues. The tissue preparation shows the fibers that serve to connect nerve cells to one another and thereby transmit information.

On the left is a section of frontal cortex from a newborn baby. The dark spots are the cell bodies of neurons (nerve cells). The strings projecting from the cell bodies are axons which send information to other nerve cells. You also see a few wispy shoots and tendrils. These fibers collect information from other neurons and send it to their cell bodies. The axon of the cell then sends the information onwards to the next cells in the chain.

On the right is a photomicrograph of the same part of the brain, but from a two year old child. Now we see a dense thicket of connections. It looks like a wild tangle, but it isn’t. These connections have proliferated in an orderly manner as the baby’s brain matured. Each and every one of these anatomical connections underwrites a behavior or a function.

Whether heart rate or a memory or hearing or language or reaching for a toy, or saying something, or recognizing a face, or experiencing love. You name it; it’s got a basis in neural connections like these. Our growth and development depends on this exuberance of connectivity. The brain grows and develops all our life but never again after these first few years will there be such luxuriant growth.

We have 10 billion nerve cells when we are born, but relatively few are connected up. Connections are especially sparse in higher brain centers – the parts that control thinking, motor control, emotion control, and perception. By age three there are literally trillions of connections. Connections among nerve cells are not hard-wired or continuous. Instead, fibers from each neuron connect at synapses through a little jolt of electricity which is regulated and modulated in strength and speed by dozens of chemical neurotransmitters and neuro-hormones.

Most neural connections are made because of stimulation from the outside world of experiences. True, they are based in our genetic makeup, but connections that occur are profoundly influenced by experiences. As an obvious example: the language a baby hears, whether English or Spanish, will be the language the baby speaks. The faces she sees will be the faces recognized. The experiences of face, voice, and touch will be linked.

Connections that are made over and over are facilitated; temporary and unused synapses are “pruned” away. Connections become strong, sure, and swift when they are used. Experience shapes the brain.

Habitually used connections use less energy. After a while, we just get on the bike and ride away, we automatically say “please” and “thank you,” we become experts with fork and knife. Our brains are freed up for the next thing.

Research shows that brain development is enhanced by good nutrition, emotional nurture, and rich and varied experiences. Conversely, impoverished, insecure, and unloving environments during early life can lead to stunted growth and development. We can prevent bad outcomes by helping children to get what they need to flourish.

This awareness has become the cornerstone of my work.

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