Adapting the VOR

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來自 The University of Chicago 的課程

了解大脑：日常生活中的神经生物学

619 個評分

The University of Chicago

了解大脑：日常生活中的神经生物学

619 個評分

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.

從本節課中

The Vestibular Sense & Gaze

The vestibular system and gaze control give us so much but are grossly under appreciated. They are so fundamental that we discount them, assuming that they will always be there. When the vestibular system fails us, its importance dominates our lives. Living with either a vestibular or an eye movement disorder is very disruptive to everyday life. In this module, you will learn how the inner ear is designed to detect and respond to head movements. You will learn about the circuit that connects the inner ear to the motoneurons that control the location of your eyes, allowing us to reflexively maintain our view of an object even as we move about in the world. Finally, we will talk about how you can modify this reflexive control of the eyes and how you can control where you are looking.

The VOR Is Fast4:46

Horizontal VOR Circuitry4:44

Adapting the VOR4:56

與講師見面

Peggy Mason
Professor
Neurobiology

[MUSIC]

Okay, so, is the view, VOR is a reflex.

And I think a common idea Is that reflexes are invariant.

They are always the same,

they're reflexive, they're automatic, they are unchanging.

And while they can be automatic, they are definitely not unchanging.

So, all reflexes can be modulated, and the VOR can be modulated a lot.

So lets just give a couple of examples of when the VOR might be modulated.

Let's think about if I am looking at a far target, and

I'm not quite sure if the target is far, far enough.

But Andy, if you could focus tight on my eyes.

I'm going to move my head back and forth while I focus on a target.

And what you will see is that my eyes move, but not by a ton.

All right?

Now, I'm going to focus on a near target as I move my head back and

forth, and what you will see is that my eyes move much more.

So, the amount that I have to move my

eyes to oppose a head movement is dependent on where I'm looking.

For near objects,

the amount I'm going to have to move my eyes is a lot more than for far vision.

So we can, we can look at what that looks like.

Here is a situation where I'm looking at a far object.

As my head moves back and forth my eyes

don't have to move very much, and I can still keep my gaze steady.

OKay? That's just simple geometry.

Whereas, when I'm looking at a near object,

I have to move my eyes much more to keep my gaze steady.

We can name this as gain.

So, the gain of, of the V, VOR or any reflex is the output.

Over the input.

So, if the input is the head movement and

the output is the eye movement, the gain is higher when I'm

looking at a near object than when I'm looking at a far object.

But as I walk around I don't think oh, gee I gotta get that VOR gain up.

because I'm, I'm going to, I'm going to start reading and and

my head might be moving.

That's the, that's where reflex,

reflexive that's where the concept of this being a reflex is useful.

The modulation of the VOR is also automatic.

It requires a part of cerebellum which is called the flocculus.

The flocculus and its partner the nodulus, but we'll just focus on the flocculus.

So in this situation, we're looking at the underside of the brain.

This would be where the spinal cord starts, here is the cerebellum.

Here is the occipital cortex, the nose would be up here.

Here's the basilar membrane and the pons.

And what you can see, Is right here.

This little bit of cerebellum on the underside, that's called the flocculus.

And that's absolutely necessary for changing the gain of the VOR.

So, we're going to go over to the board for a moment.

And we're going to see, here is the cerebellum, here is the flocculus.

Neurons in the flocculus are very privileged.

They get actually input directly from the ear, and

they they send a signal to the vestibular

nuclei to modify the signal right away.

Right as it comes into the brain.

And it's right here that they change the gain for the output, the VOR,

that, that, depends on these connections to motor neurons.

So, that's changing the gain of the VOR.

And what we're going to now turn in our final module is, how we change gaze.

And in order to change gaze,

one thing that we might want to do is actually even turn off the VOR,.

And we'll look at that in the next module.

[MUSIC]

[MUSIC]

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