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Brain Child: Science Findings on Brain Development

 
by Tamara Koehler, Scripps Howard News Service, May 25, 2003

An infant is staring at his mother's versatile face, not a trace of understanding in his still-focusing eyes.

And yet behind that wide-eyed gaze and soft cap of bone, an electrical storm is taking place.

Deep inside the 1 1/2 pound infant brain, millions of wispy circuits are zapping and firing, paving electrical roads and bridges that will carry the heavy traffic of learning, questioning and creating throughout life.

The first five years of life is, arguably, the richest period for learning a short but spectacular window of time when experiences such as a whisper, a hug and a bedtime lullaby literally change the architecture of the developing brain.

"We now have concrete images of the way the brain is hooked up early in life, and it is truly a remarkable period like no other in life," said Dr. Harry Chugani, a neuroscientist at Children's Hospital of Michigan in Detroit.

Recent scientific findings have enhanced learning about brain development and proven what may sound like common sense to many: Young children are greedy learners whose brains soak up all the language, information and behavior they experience in the world around them.

In the past decade, new brain-imaging technologies have shown that:

It's nature, then nurture. Genes provide each brain's basic building materials. The environment builds it through trillions of brain-cell connections made by sight, sound, smell, touch and movement. Positive experiences enhance brain connections, and negative experiences damage them.

Young brains work at warp speed. An infant's brain can form new learning connections at a rate of 3 billion per second. A child's brain uses twice as much glucose (fuel) as the brain of a chess master plotting three moves in advance.

Words work wonders. Babies whose mothers and fathers talk to them more often have bigger vocabularies and tend to learn to read sooner and better.

Movement matters. Children who spend too much time in playpens and not enough on jungle gyms don't develop the motor cortex area of the brain and, as a result, show poor school readiness.

Music matters. Piano instruction in particular can enhance the brain's ability to visualize ratios, fractions and proportions, and thus learn math and logic.

Neglect hurts. Depriving an infant of loving talk and touch releases steroids that damage the brain's hippocampus, which controls its stress-response systems, and can lead to serious cognitive, emotional and social problems.

Stress hurts. Chronic stress such as poverty, abuse or violence can impair the development of the amygdala, an almond-shaped area deep in the brain that houses emotion and memory. It also can confuse chemicals that moderate impulsive behavior, fear and aggression.

There are brief and early "critical periods" when parts of the brain that control vision and language are open to stimulation, then close forever. There are somewhat longer "sensitive periods" for learning math, music and second languages.

The brain is smarter than we think. New research is trying to understand the brain's amazing "plasticity," its ability to repair and rewire itself.

The extraordinary development of the human brain begins a few weeks after conception. Neurons the brain cells that store and send information begin multiplying at 50,000 per second, a frenzy that continues throughout gestation.

Many of these newly formed neurons are pre-wired by genes to control survival functions such as breathing and heartbeat. Others migrate to areas in the developing brain and body where they await further instructions from the world outside the womb.

Once in place, neurons begin developing the hardware necessary to transmit the electrical language of the brain.

Neurons send signals to other neurons through axons, a thin fiber that relays electrical messages. Once an axon finds its target cell, it develops dendrites, or branches which can receive a wide variety of information from other brain cells. The more dendrites a nerve cell has, the better and quicker it is at learning, said Dr. Lise Eliot, a neurosicentist with Chicago Medical School.

At birth, the infant brain has few dendrites. Its neurons look like saplings. Adult neurons resemble trees with hundreds of branches formed through experience and learning.

"A well-stimulated child's brain and an adult's for that matter is visibly different under the microscope," Eliot said. "A well-connected brain is a forest of dendrites ... In severely neglected children those dendrite branches are not as dense which means the quality of connections and the ability to learn is affected."

Another key ingredient in a well-formed connection is myelin, a fatty substance that coats axons like plastic insulation around an electrical wire. Myelin sheaths enable brain signals to travel 100 times faster.

Babies are born with few myelinated axons. That's one reason infants can't see well and can't do much with their hands other than grasping and batting at objects.

As children get older, different areas of the brain become myelinated on a genetically determined timetable. These periods of mylenization are critical periods for learning. For instance, the first axons to be myelinated in the language area of the brain are those that enable language comprehension. Six months later, myelination extends to the language-production area known as Broca's area.

Again, environment plays a large role. Children who are malnourished have less myelination. This can explain some learning problems, such as being a slow reader, Eliot said.

Myelination continues well into the teenage years, primarily in the frontal lobe where decision making and reason develop.

The human brain actually overdevelops at first.

At birth, there are up to 200 billion nerve cells in place throughout the body, many of which start firing and connecting in the brain with the baby's first breath.

From that point on, environment begins to play its starring role in the way the brain is wired for emotion, behavior and learning.

In the first decade of life, these brain and nerve cells make many more connections than are needed something scientists call "synaptic exuberance." The first connections made after birth are sensory ones that let the child know "milk tastes good" and "this smell is Mommy."

But only those connections that are reinforced over and over again will remain.

Better coordination in adulthood can be traced to a childhood full of activities like running and jumping when motor skill connections are being made. Every time a child runs or jumps, for example, the wiring from the brain to the muscles in the legs are strengthened.

By puberty, the brain begins pruning away unused or unneeded neuron connections a necessary phenomenon for thinking clearly, making fast associations, reacting to threats and solving problems.

But the pruning process also can work against the growing child, especially if connections that could have proved useful later in life are killed because of lack of use.

One stark example of this "use it or lose it" phenomenon is language

By 6 months of age, infants develop a map in the auditory cortex of the phonetic sounds in the native language their mother or caretaker speaks. By 12 months, infants lose the ability to discriminate between sounds that are not made in their native language.

While subtle phonetic distinctions might be lost in the first year, children have the ability to learn a second, third and fourth language quickly until about age 10, Dr. Pat Kuhl, co-director of the University of Washington's Center for Mind, Brain & Learning said said.

After that, the brain starts discarding the excess language learning connections. After 10, learning a foreign language is still possible but more difficult.

"There is so much at play genetics, nutrition, peers nothing is set in stone," Kuhl said.

"But what we do know is this is a critical time when you can help a child be ready for school, be at the highest level of development he or she can be."
 

 

 

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