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."
