Brain Development
Brain Growth
The brain grows at an amazing rate during
development. At times during brain development, 250,000 neurons are added every
minute! At birth, almost all the neurons that the brain will ever have are
present. However, the brain continues to grow for a few years after birth. By
the age of 2 years old, the brain is about 80% of the adult size.
You may wonder,
"How does the brain continue to grow, if
the brain has most of the neurons it will get when you are born?”
The answer is in glial cells. Glia continues
to divide and multiply. Glia carries out many important functions for normal
brain function including insulating nerve cells with myelin. The neurons in the
brain also make many new connections after birth.
The first three years of life are a period of
incredible growth in all areas of a baby's development. A newborn's brain is
about 25 percent of its approximate adult weight. But by age 3, it has grown
dramatically by producing billions of cells and hundreds of trillions of
connections, or synapses, between these cells. While we know that the
development of a young child's brain takes years to complete, we also know
there are many things parents and caregivers can do to help children get off to
a good start and establish healthy patterns for life-long learning
Brain
Development before Birth
At conception the sperm and egg meet to form a
single cell determining the genetic potential. About 60% of the genes are
dedicated to brain development.
Three to four weeks after conception a thin layer of cells forms on the embryo. The cells fold and fuse to form a liquid filled tube. This is the basis of the brain and spinal cord. The embryo then starts to produce nerve cells or neurons. In the first month following conception the cells in the neural tube start to multiply at an astonishing rate, reaching a maximum of 250,000 neurons a minute. Most of the brain’s lifetime’s supply of cells is produced by six months.
At 14 weeks very few of the brain cells are sparked to perform a function. The majority begin to migrate to form different areas of the brain. Most cells arrive at the correct site at the right time. Those which are damaged or go astray tend to die.1
“In very rare situations some do reach the
wrong location and form the wrong connections with the result later seen in
eventual disorders such as severe infantile epilepsy, autism, some forms of
intellectual delay and vulnerability to develop schizophrenia.”
The brain produces many more cells than it will need. By the time the fetus is twenty weeks old, about half of these cells are deliberately shed.The remaining cells are organized into forty different physical areas that will broadly govern senses and skills such as vision, language and muscle movement.
Beyond
the Age of Three – Practice makes Permanent
Repeated experiences causes the connections to
become well worn pathways, permanently etched into the brain. Infrequent
experiences result in the loss of developing pathways.
As the brain structure develops, the child will begin to reach the milestones associated with child development, such as grabbing an object, learning to speak, crawling and walking.
It is the combination of these neurons,
synapses and pathways that will combine to form the unique structure and
chemical composition of every individual’s brain.
Stages
of Brain Development
The brain does not develop at an even pace. It
tends to develop in waves with different parts of the brain developing at
different times. This development takes place, however, in a predictable
sequence.
Neuroscientists have shown that the brain is affected by environmental conditions throughout the entire process of development, even prior to birth. This includes the type of nourishment, care surroundings and stimulation the fetus or infant receives.
Brain
Development in the Infant
By birth the brain has developed the total 100
billion brain cells, or ‘neurons’, it possesses. However the brain is a work in
progress. Most of the neurons are still immature. The cells need to be
activated and the connections between neurons are weak or have not yet been
formed.
At birth the infant can see, hear, smell and
respond to touch, but only dimly. Almost immediately after birth the newborn’s
brain begins to form trillions of connections and pathways between the neurons.
These connections and pathways are vital as they enable the infant to see,
hear, smell, learn and reason in a more developed way.
Although genes begin the process of brain
development, it is the experiences of the child that now start to take over
this process. These experiences trigger the electrical activity necessary to
enable the brain to develop connections and grow.
These connections are called synapses. The
connections are formed by each neuron putting out a long tentacle like fiber
called an axon. The neuron uses the axon to send messages to other neurons. The
messages are sent as electrical signals and picked up by thousands of short,
hair like fibers could dendrites.
Each neuron is able to connect up with
thousands of other neurons.
