0:12
Okay, so we've gone through the motor hierarchy, but
we know that using the motor hierarchy alone.
We are not gonna move the way that we actually do move.
We would still be very uncoordinated and
we may not move at all without the basal ganglia.
We need to look at two areas that modulate movement and
the first area that we're gonna look at is the cerebellum.
So here is the cerebellum, you can see it.
It's a little brain that piggybacks on top of the hindbrain,
it's actually derived from the hindbrain.
So here's hindbrain, this part here is
the pons and this is the cerebellum.
And the cerebellum [COUGH] is very interesting
in the sense that it looks like it's a sensory area.
It gets so much sensory input, it gets input from the joints,
from the muscles, from the skin, from deep tissues.
It gets input from the vestibular apparatus and
it gets input from the visual system.
It gets all manner of sensory input and
yet, we're talking about it in the motor section.
Because in point of fact, when we
have damage to the cerebellum, there's a very obvious problem.
And that problem is completely motor in appearance.
And the problem that we get, as you know, with a cerebellar lesion is called ataxia.
2:04
Now the one point I wanna make in this first segment is to emphasize how
the cerebellum is a data-driven structure.
Innately, the cerebellum has no program.
It uses information from an individual's body to
program that body into making smooth movements.
And why is it set up that way?
Why not just give it a nice program, so that we come out and
we're able to walk and stand and do all this other stuff.
Well, there are a couple of reasons, but mostly,
the fact is that our bodies [COUGH] change over time.
2:50
So this is Minnie as a kitten, this is Minnie as an adult.
You can see just in the structure of her face, the structure of her face,
the proportions have changed.
The proportions of her body have also changed and that happens to all of us.
We grow from being 20 inches, which is I have no idea in meters.
[LAUGH] Some number of centimeters.
3:16
We go from being that long to being a meter or two, a couple meters tall.
So we undergo a huge change in just our basic anatomical structure.
And the cerebellum can adapt to that,
because it has no a priori assumptions about what our body is gonna be like.
It's going to work with the body that you're given.
So if you're a conjoined twin, then it'll hook up
your motor system to work with the body joined wherever it is.
If you're gonna be tall, you will develop, the cerebellum will
adapt its motor coordination for a tall person.
4:08
And an additional reason is that you have to live a very charmed life.
In order to never have some kind of an injury or
a setback in your muscles and
your bones, tendons, ligaments.
All that.
So you may end up actually not being able to walk or
not being able to use your arm for some months.
4:39
You have to still be able to move even though your body has changed.
And so by making the cerebellum data-driven without any assumptions.
You're able to change your motor programming according to what
the state of your body is at any one time.
Now, the final point that I wanna make here is that the cerebellum,
we can think of it as a computer chip.
It takes in all this information and then it does something with it.
Transforms it, it makes it into some output.
And the nature of that transform
is something that we still are trying to understand.
But the fact is, that the cerebellum not only gets data from our bodies.
But it also gets data from our cerebral cortex, from our neocortex.
And the possibility exists and we'll come back to this at the end.
That the cerebellum does a transform on non-motor information.
So that it does a similar transform that it does to all the sensory information for
a motor output.
It makes a similar transformation about emotions, and thoughts, and communication.
6:02
That is a area of great interest, great controversy.
And it's still to be work out, but
it is a distinct possibility that the cerebellum contributes
to non-motor function, as well as to motor function.
[MUSIC]
Peggy MasonProfessor
