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I just want to contrast, in this segment, I
want to contrast the cerebellum and the basal ganglia.
These are the two great loops of the brain.
And in both situations, there's a ton
more information coming into them than comes out.
In the cerebellum we know that it's 40 to one.
In the basal ganglia it's probably a sim, on a similar
order of magnitude, so everything has to go through these two loops.
What are they doing that's the same?
What are they doing that's, that's, different?
Well, in this case of the cerebellum,
you have access to very rudimentary sensory information.
Information about where your body is.
What, where you're, how stretched your muscles are and
how your joints are, are, situated, that kind of thing.
In the case of the basal ganglia, the input is very, it,
the message of the input is very carefully controlled by the cortex.
The cortex is telling the basal ganglia what, is controlling.
It's essentially a censor for all that sensory input.
If it can't make it through the cortex,
the basal ganglia is never going to know about it.
That gets censored out.
So, so the cerebell or, cerebellum has access to very mundane information.
And there's no censor.
And as a result, the cerebellum is acting on every single movement, whether it's a
movement of great, whether it's a movement of
great profundity, or whether it's a trivial movement.
Whether it means something to, to you, or whether it's
something that is just, en route to getting something else.
As, and in contrast with the basal ganglia, things have a
meaning and, and normally, when the basal ganglia is firing on all
pistons, then the moods, your motivation, your emotion, your
perceptions, and your actions are all oriented towards one goal.
You're working fully, fully on it with your full brain
focused, fixated, on one outcome, and you use every piece of your brain function.
All that motivation, all that mood, all
that affect, all that emotion, and the perceptions.
You don't see the things that you're not interested, they're, that are irrelevant.
3:02
So the basal ganglia are, going to be
critical for making movements that, that are of import.
And they're really not going to care so much
about trivial movements, movements that we're going to forget
about in a moment, whereas the cerebellum makes
no value judgment about the movements that we make.
All of that said, one of the consistent findings that we have from
imaging studies is that every time, the basal ganglia are involved, or, in
almost every action that we make, the cerebellum is involved, and maybe that's
just, the cerebellum is involved just because of the nuts and bolts of movement.
But there is some growing idea that the cerebellum is also involved in evaluating
thoughts and emotions, and that these also, go through the, the cerebellum.
And indeed, the cerebellum does receive information about thoughts and emotions.
It just receives all this other sensory input
that kind of outweighs that under normal circumstances.
4:22
in some of these, complex, illnesses and disorders, such
as substance abuse, I think, would be a mistake.
It, I think that it's probable that the cerebellum does
make a contribution to all of these things, including substance abuse.
So that when a person finds themselves in an environment, and where they have taken
drugs and been rewar, been pleasantly, had a pleasant outcome
from taking drugs, there is a memory of that pleasant outcome, but there's also
that sensory environment that plugs into a, a, a cerebellar motor learning.
And there might be a motor component, a motor-learned component of,
drug taking that the cerebellum, contributes to.
But certainly, we know that the basal ganglia contributes to
and, and, the only point here is just to say
that the cerebellum also probably works with the basal ganglia to support
this overwhelming compunction to take, drugs of abuse.
Okay, in the final, segment, we'll just wrap up
all of movement in, in, in a few minutes.
[MUSIC]
Peggy MasonProfessor
