Efference Copy and Sensory Reafference

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Do curso por The University of Chicago

Compreendendo o Cérebro: Neurobiologia da Vida Cotidiana

624 classificações

The University of Chicago

Compreendendo o Cérebro: Neurobiologia da Vida Cotidiana

624 classificações

Learn how the nervous system produces behavior, how we use our brain every day, and how neuroscience can explain the common problems afflicting people today. We will study functional human neuroanatomy and neuronal communication, and then use this information to understand how we perceive the outside world, move our bodies voluntarily, stay alive, and play well with others.

Na lição

Motor Modulation

You should now have an understanding of how muscles function to initiate movements. However, the brain requires more than just the cerebral cortex to determine what movements to perform and to make those movements smooth and guided. This module, we'll explore the cerebellum and the basal ganglia, fascinating structures that play a major role in movement. You'll also learn how these brain regions are involved in motor learning and disease.

The Data-Driven Cerebellum6:25

The Purkinje Cell4:05

Cerebellar Functions5:48

Cerebellar Topography5:49

Cerebellar Laterality3:20

Efference Copy and Sensory Reafference6:22

Conheça os instrutores

Peggy Mason
Professor
Neurobiology

[MUSIC]

Okay, let's try and understand how the cerebellum does what it does.

It gets 40 times more information than it sends out.

So there's 40 times more input than there is output.

Is, if we count numbers of axons.

So let's think about, what are the types of inputs that the cerebellum gets?

It gets two basic types of inputs.

One is what we call, let's call it efference copy.

So.

We have to make sure that everyone understands

the difference between an afferent and an efferent.

Only one letter.

But afferents come in, efferents go out.

So efference copy, what that means is, as you, as

you, as your brain initiates a movement.

That command gets sent to motor neurons, or to

motor, inner neurons and then out to the muscles.

But a copy of that command also gets

sent to the cerebellum, and that's an efference copy.

But the cerebellum is very interested in what you intent to do.

And it, it wants to make sure that the game of telephone worked.

So not only do, does the cerebellum get efference copy from the cerebral cortex.

So, primary motor cortex which is going to go down to this

spinal cord and tell the motor neurons how to move the muscles.

It's going to send a copy of its message to the cerebellum.

In addition, the motor neurons themselves, actually send a copy

of the message that they received, back to the cerebellum.

So, we make sure that the message that the, that the motor neuron received and

the message that the, the cerebral cortex sent, both

of those messages are sent to the, to the cerebellum.

So this is a, an example of efference copy.

I, I for some reason I always think of, airplanes and, wing flaps.

So, the wing flaps have to go down.

Somebody, the pilot presses the button, and the wing flaps go up or down.

And then there is a sensor out there to make

sure that the message was received by the wing flap mover.

And so that is too different versions of ef, of efference copy.

Now in addition, that's, that gets compared, the critical thing that

the cerebellum does is to compare that efferernce copy with sensory reafference.

And what I mean by sensory reafference, I mean the afferent stuff that comes in.

Not, not initially, but as a result of an action that we have done.

So, this is reafference.

So, another words, If I move my arm.

The reafference is, that this joint is now extended.

That this muscle is extended, this muscle is contracted.

That's reafference.

It is the input that results from the movement that I made.

So in the, in the, the airplane analogy, sensory

reafference would be a little sensor that says indeed, not only did the

the, do hickey that moves the wing flap receive the message.

But in fact, the, the wing flap, wing flap is up.

So, you're getting the information back, the sensory information back.

Now, what's the point?

Well, the point is that the sensory reafference

and the efference copy, they should all match.

We should make the movements that we intend to make.

The intended movement, the actual movement should match the intended movement.

When it.

When they actual movement does not match the

intended movement, the cerebellum makes a course correction.

And that is, that is how it produces learning.

And the type of learning that

the cerebellum does is called associative learning.

So, essentially, what it's doing, you can think about it like this.

The cerebellum is trying to associate a sensory picture with a part of a movement.

As I go to serve a tennis ball, it should feel like this at this point.

And then, as I move my hand forward, it should feel like this.

And then it should feel like this.

And then it should feel like this.

So I should anticipate what the right sensory

feedback should be, if I'm doing the movement correctly.

And in, you can think about it in terms

of, if you, if you make an incorrect movement.

Let's say I botch a serve, I usually know the moment where it didn't feel right.

And why didn't if feel right?

Not because I didn't do it right but because the

sensory feedback feels wrong, it felt wrong at a given instant.

And that's because it, it we've, we've deviated from the association

between the correct sensory feedback and the, and the intended movement.

So it, it's, this marries the idea that the

cerebellum is all about motor control but it uses sensory information

to produce a smooth and coordinated motor control.

In the next couple of segments we're going

to look at two different examples of cerebellar

learning

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