04 - What is Learningدوره: Coursera – Learning How to Learn / درس 4
04 - What is Learning
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متن انگلیسی درس
Welcome to learning how to learn.
My name is Terry Sejnowski.
Let me introduce you to your brain.
First, some brain surgery.
We take off the skull and
take out the brain.
This brain weighs three pounds,
but it consumes ten times more
energy by weight than the rest of
the body, a very expensive organ.
It is the most complex device
in the known universe.
All of your thoughts, your hopes, your
fears are in the neurons in this brain.
We prize our abilities to do chess and
it takes years of practice
to acquire these skills.
And digital computers are much
better at it than we are.
It came as a surprise to discover
that what we do so well and take for
granted, like seeing,
hearing, reaching, running,
are all much more complex
problems than we thought and
way beyond the capability of
the world’s fastest digital computers.
What this illustrates is that we are not
consciously aware of how our brains work.
Brains evolved to help us navigate
complex environments, and
most of the heavy lifting is done
below our level of consciousness.
And we don’t need to know how
it’s done in order to survive.
Psychologists who study the unconscious
mind have found that influences
include thought processes,
memory, emotions and motivation.
We are only aware of a very small fraction
of all of the activity in the brain, so
we need to rely on brain
imaging techniques to guide us.
Here is the activity map of someone’s
brain who was asked to lie still,
at rest, in a brain imaging scanner.
On the left is the side
view of the brain and
on the right is the view from the midline.
The colors indicate brain areas whose
activities were highly correlated,
as shown by the time courses below,
color-coded to the brain areas.
The blue areas are highly active when
the subject interacts with the world, but
turn off in a resting state.
The red-orange areas are most
active in the resting state and
are called the default mode network.
Other brain areas are also more active
when you are resting, and these areas can
be further divided into groups of areas
that have common patterns of activity.
This is a new and
intense area of research, and
it will take time to sort out all
the resting states and their functions.
There are a million billion synapses in
your brain where memories are stored.
The old view of the brain
is that once it matures,
the strengths of synapses can
be adjusted by learning, but
the pattern of connectivity does not
change much unless there is brain damage.
But now we know that brain
connectivity is dynamic and
remains so even after it matures.
With new optical techniques for
imaging single connections between
neurons called synapses, we can see
constant turnover, with new synapses
being formed and others disappearing.
This raises a puzzle.
In the face of so much turnover, how do
memories stay stable over so many years?
This is a picture of one
dendritic branch on a neuron which
receives inputs from other neurons.
The synapses are on the spiny
knobs coming off the dendrite.
On the top,
the dendrite was imaged before learning.
The same dendrite is shown below
after learning and after sleep.
Multiple synapses that are newly formed
together on the same branch
are indicated by the white arrowheads.
You are looking down into
the brain of a live animal.
This is really a fantastic new technique.
Synapses are less than
a micron in diameter.
In comparison, a human hair is
around 20 microns in diameter.
This new technique allows us to see
how learning changes the structure of
the brain with a resolution that is
near the limit of light microscopy.
This illustrates that, intriguingly,
that you are not the same person you were
after a night’s sleep or even a nap.
It is if you went to bed with one
brain and woke up with an upgrade.
This is a better deal than
you can get from Microsoft.
Shakespeare, the great English poet,
already knew this.
Here is Macbeth lamenting his insomnia.
Sleep that knits up the raveled sleeve
of care, the death of each day’s life,
sore labor’s bath, balm of hurt minds,
great nature’s second course,
chief nourisher in life’s feast.
Here Shakespeare is making an analogy
between knitted clothes and
sleep that knits up the loose
threads of experience and
concerns during the day and weaves them
into the tapestry of your life story.
You will learn in this first week how to
take advantage of your unconscious mind,
and also sleep, to make it easier to
learn new things and solve problems.
During the lectures you may ask yourself,
how does the brain do this?
A good place to find out more about your
brain is the website brainfacts.org,
brainfacts, one word, .org.
You will find a wealth of interesting
things about brains and behavior, and
in particular about learning and memory.
I am Terry Sejnowski.
Happy learning until we meet again.
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