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Okay.

So lets talk about saccades.

In order for saccades to be effective, we actually have to cancel the VOR.

And we mentioned that before, I just want to show you what that looks like.

That means that as we move the head the eyes do not move in opposition,

so that the gaze will move with the head position.

Okay. So now we've cancelled the VOR, we're

going to allow our eyes to change the, change gaze and what do these look like.

These are ballistic movements and in the next slide, I just have a picture of me.

So this shows me reading and what you'll see is a bunch of,

of small eye movements as I go across the page and

then come back to the left.

Look at each word.

So, it's like bup, bup, bup, bup return, bup, bup, bup, bup return.

Those little movements are very fast, you can see them.

They're saccades, each one of those is a saccade.

And saccades have a a velocity of something, you know,

they can have a velocity of, of 300, 400 degrees per second.

Which means that if they lasted for a second,

you twirl your whole eyeball all around.

Obviously, they only last for a very short amount of time.

So here is a diagram of, of what these saccades look like.

If once a target appears there's some time that it takes

to process how one's going to get there, this is all brain, brain stem processing.

That, that we use to figure out how to move the eye.

And say, about, roughly, roughly 200 milliseconds or

a fifth of a second later, we start our saccade.

And the saccade goes really rapidly to where we want it to go.

And then it gets and then we maintain our gaze at where we want it to shift to.

So there's the pulse step, there's the pulse component and the step component and

the important point about this saccade is that it's ballistic.

It's like that, it's just, just as the bullet wants

to leave the rifle has no more mind of its own.

Once this saccada starts, even if the target shifts,

the saccade can end up in the, in the same place.

So now during that saccade where it all bets are off.

We're going where we're going.

Eh, everything was set in motion by the moment that the saccade started.

It's a ballistic movement.

Okay.

So what are these used?

Saccades are, are what we use to look around the world.

And this is another example of where saccades can differ across people.

People that are in certain disorders,

people don't look at faces the same way healthy individuals do.

So, under healthy individuals will spend a lot of time looking between the two

eyes down to the mouth and make this kind of triangle.

Occasionally, go around the the whole circumference of the face.

But most of their gaze shifts are between the two eyes and mouth and

then there are certain conditions where most of the gaze shifts when looking at a,

at a face are concentrated say, at the nose.

Or they may be concentrated at the nose during happy expressions and

not during sad expressions.

So there are all, all manner of ways in which this saccade generation can tell

you a lot about a person's ability to take in information from the outside world.

Another very simple thing that these saccades do is there's a different type of

saccade.

So the, these can, these saccades and the saccades that you looked at when I was

reading are pretty big shifts, they're five, ten degree shifts.

But there are also saccades, they're called micro saccads.

They're less than a degree and they, they go and then they return back to a place.

And these are called microsaccades and these microsaccades

are critical to making sure that the visual world does not fade.

When we looked at vision, remember that we saw that with time if we don't move.

And if the scene doesn't move, the visual world will fade into nothing.

We won't see it anymore.

Well, these microsaccades make sure that,

that, that we do move that our gaze moves and so that they.

Seeing outside continues to be perceived through the visual system.

Okay.

So now in the next segment, we're going to look at the circ,

circuits within the brain that give rise to saccades.

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Saccades

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