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[♩INTRO]
The feeling of a kicking fetus is perhaps
one of the more fun parts
of having a baby.
And these movements serve a purpose well beyond
letting you know
that that little thing is in there.
Like the pilots in Pacific Rim learning to
control their giant robotic Jaegers,
these movements are evidence that your tiny
incipient human’s brain
is learning to control its body.
When a fetus is in the womb, it’s not just
sitting around waiting to be born.
It’s actually working really hard to learn
everything it needs to survive
in the outside world, including breathing,
swallowing, and, of course, moving.
There are over six hundred muscles in the
human body,
which makes for a lot of controls to master.
So fetuses need to get an early start,
and the womb is the perfect place to get some
practice in.
The first fetal movements happen around seven
weeks after the parent’s last period.
Which is pretty early!
They consist of slow bending movements of
the head and trunk,
and eventually simple movements of the arms
and legs.
Things start to change at a postmenstrual
age of nine to ten weeks.
That’s when the fetus starts to move with
all the parts of its body,
and the directions and speeds of these movements
start to vary.
These movement patterns are called general
movements,
and their purpose is to explore all the possible
combinations of movements
the fetus’s tiny body can make.
These movements generate proprioceptive sensory
signals,
that is, sensory information about the position
and movement of the body.
Every possible general movement has its own
set of proprioceptive signals,
which helps the brain learn what these movements
feel like.
So not only is the brain sending out all sorts
of commands
to the muscles in the body, but the body is
teaching the brain
the consequences of those commands.
The brain is learning what groups of neurons
are responsible for what movements.
It’s essentially the equivalent of learning
to control a Jaeger
by flailing your arms and seeing what happens.
It doesn’t end there, though.
General movements continue to evolve and change
throughout pregnancy and into the first few
months after birth.
More or less.
See, these changes in general movements occur
at fairly predictable
postmenstrual ages, but are not affected by
birth.
Infants who are born prematurely tend to follow
the same
motor development patterns as their counterparts
who are still in utero,
but are the same postmenstrual age.
It seems like the brain still needs about
the same amount of time
to learn to control the body, regardless of
whether or not it is still in the uterus.
It’s not until several months after birth
that these general movements
are replaced with goal-directed movements,
movements used to accomplish specific goals,
like rolling over or reaching.
However, there are a few goal-directed movements
that have to be learned in the uterus.
Sucking and swallowing are vital because they
help a newborn eat,
and therefore survive.
So they have to develop before birth.
Fetuses have to learn to breathe, too, which
they seem to do via hiccuping.
Other than that, infants tend to learn goal-directed
movements
in a consistent order after birth,
starting with eye tracking and head balance,
and advancing to rolling over, grasping objects,
crawling, sitting, standing, and eventually
walking.
Turns out it’s hard work learning to pilot
a human body.
Thanks for watching this episode of SciShow!
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to Brilliant?
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they might be a good place to start.
Like their course on algorithm fundamentals,
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So go forth and design your Jaegers!
[♩OUTRO]
