As you read the words on this page, you are utilizing thousands
of the 100 billion (more or less) nerve cells that make up
your brain. The electrical firings and chemical messages running
between these cells, called neurons, are what produce our
thoughts, feelings and interactions with the world around us.
One hundred billion neurons may seem like a lot of nerve
cells, but is actually only about 20% of the number we originally
start with. The number of nerve cells in our brain peaks prenatally
and then they start to prune themselves out, one by one, through
childhood. By the time we enter adolescence, our brain has
chosen the final select neurons it will keep throughout our
adult life. The decision is based on which cells we use and
which we do not. The cells we do not use are pruned away leaving
more room to add branches, or dendrites, to the nerve cells
that we do use. New branches are added as the brain receives
and processes any new information.
How does the brain actually "prune" the garden? The answer
lies in a number of chemicals and their actions and reactions.
The chief pruner is probably an enzyme named Calpain. Calpain
has the ability to self-destruct a cell. Technically this
is known as autolysis ("auto" meaning self, and "lysis" meaning
to destroy).
Calpain is produced in the nerve cells when there is a heavy
calcium ion concentration in their surrounding environment.
Reduced blood flow can cause this high calcium ion build up
between and within cells (for you biology enthusiasts, the
calcium comes from the mitochondria and the ER as well as
an influx from outside the cell). In other words, high activity
in a brain region calls for heavy blood flow to service the
cells, low activity requires little blood flow. Therefore,
the less-used areas, with their limited blood flow activity,
tend to build up calcium ions. This build-up triggers the
secretion of the enzyme Calpain, which causes the nerve cell
to self -destruct.
New growth, on the other hand, comes in the dendrite development,
or branching of well-used neurons. This branching is caused
from chemicals known as Neurotrophins. Neurotrophins are a
group of proteins which are responsible for the growth and
development of neurons. As you may suspect, we use a lot of
neurotrophins during childhood as the brain has massive growth
and development. But we continue to use neurotrophins all
of our lives, especially in the hippocampus area, the brain
region responsible for new learning and new memory formation.
There are many neurotrophins at work in the brain. The first
one discovered is known as NGF (nerve growth factor). Others,
discovered since, have equally self-explanatory names as brain
derived neurotrophic factor (bFGF), and glial cell-line derived
neurotropic factor (GDNF). These neurotrophins work by attaching
themselves to receptor sites on nerve cells and causing the
cell membrane to change shape, grow and branch.
Because most growth hormones throughout the body are especially
active during sleep, it is thought that the majority of neurotrophic
work is also done during sleep, especially the non-REM cycles
of sleep. The work of Marcos Frank and Michael Stryker, at
UC San Francisco, caught the education world by surprise in
2001 with their startling research showing the tremendous
amount of branching and subsequent learning that took place
during sleep. While most of the science community historically
considered that the REM, or dreaming cycle of sleep was the
time when most wiring took place, Stryker's work and the research
following that study continue to show that it is actually
the non-REM cycles that help hard wire in the information
learned the previous day.
From a practical standpoint, sleep research continues to
show the importance of sleep to the learning brain. Students
MUST get sufficient sleep following the learning of new information
if we want that information stored in a long-term, complex
network of neuron branches.
The research on brain wiring and the biology behind it continues
to be a fascinating topic. It gives hope to people with stroke
damage, Alzheimer's and other neurological problems, as well
as providing a better understanding for those of us who parent
and teach young brains.
Remember to learn something new today. . . then sleep on
it.
Kathie F. Nunley is an
educational psychologist, author, researcher and speaker living in
southern New Hampshire. Developer of the Layered Curriculum method
of instruction, Dr. Nunley has authored several books and articles on
teaching in mixed-ability classrooms and other problems facing today's
teachers. Full references and additional teaching and parental tips are available at: http://Help4Teachers.com. Email her at: Kathie (at) brains.org
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More tips and ideas at: http://brains.org
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