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PROFESSOR: OK, today let's continue
with the motor system.
The quiz for this week will be posted.
Just a few questions.
One of them might require you to do a little bit on the web,
but it should be pretty easy for you to finish it by--
I'll accept them through Saturday.
We were talking about hierarchical control of local
motor behavior.
And I pointed out how local motor pattern controllers and
initiators in the hypothalamus or sub-thalamus--
they call it the mid-brain--
get a lot of input from the end-brain, as I
show here in blue.
And I just want to point out that this picture might lead
you to believe that locomotion is always
originating in the end-brain.
Show it being initiated by olfactory inputs, other kinds
of sensory inputs that come in through the older pathways
through the old thalamus and striatum.
And the newer pathways reaching the neocortex.
But I note here that some inputs from the visual system,
they actually reach that area, the mid-brain locomotor area
more directly without going through the striatum.
They come through a part of the [? pretectural ?]
[? legion ?].
And it's very likely that other systems do the same, but
we know-- remember those lesion experiments I talked
about some time ago?
Animals with decerebrations where the whole
end-brain was removed?
They didn't initiate much locomotion at all.
You'd have to push them, nudge them in various ways to get
them to locomote.
But of course that might be partly an artifact of that
huge brain lesion you're making.
So I think there's some initiation of locomotion
without too much above the mid-brain.
It's been--
it's not been studied as much as these pathways shown here
in the far left.
So this is the pathway from olfactory bulbs that goes
through the ventral striatum, that then goes to this area,
the caudal hypothalamus.
We call that, that's the region of the hypothalamic
locomotor area.
And then, to this region of the caudal mid-brain, the
mid-brain locomotor area.
Just to show you on that diagram I've been using, of
the ancestral brain, where these pathways are found.
And have been found since very early evolution.
But we know the generation of the actual pattern of
locomotion, control of those movements,
is spinal and hindbrain.
It depends on [? propria ?]
spinal input, from muscles and joints.
It depends on tactal inputs from the limbs.
So I want to talk now a little bit about these circuits that
influence locomotion in various ways.
We know its execution can be modulated by reflex inputs to
the spinal cord directly, from the field.
They come in through the dorsal roots and use propria
spinal connections to reach motor neurons.
But I want to say now more about these hindbrain
mechanisms, coming through to the stibula nuceli, and the
cerebellum.
Let's just take a look at what they're like.
The stibula nuclei get input through the eighth nerve.
So the eighth nerve carries both auditory and vestibular
input from the inner ear.
The stibula nuclei are actually a collection of four
different nuclei.
One of them has very, very large cells.
It's called Deiters' nucleus.
This nucleus gets direct input from the vestibular nerve.
It has direct projections to the spinal cord.
So it's just one synapse, the vestibular system can reach
the spinal motor mechanisms.
We call that the vestibular spinal track.
It comes from Deiters' nucleus.
We also get pretty direct input to the motor neurons
controlling eye muscles.
These follow the MLF, the media longitudinal fasciculus,
it's called.
And you'll see that in the diagrams here.
Directly connects vestibular nuclei and
the ocularmotor nuclei.
So a lot of the stabilization of our eyes
as we move our head--
when I do this, my eyes stay pretty much in the same
position, looking out at the class.
Part of that's visual, of course.
I'm maintaining fixation.
But even if I close my eyes and if you kept track of the
position of my eyeballs, you'd see pretty much
the same thing happening.
It's under vestibular control, not just visual control.
So these are the [? Nauder ?]
pictures, where he shows the brainstem of a human as if it
were transparent.
And he's showing the secondary sensory cell groups and the
groups of motor neurons.
And I've shown the vestibular nuclei there
with the blue stippling.
So you can see its location there,
on the rostral hindbrain.
These are the cerebellar peduncles.
So that's where all the fibers come to connect the cerebellum
to the brainstem.
All these fibers in this really big bundle here in the
side come from the pons.
Hearing input from the cortex up to the cerebellum.
That's been removed.
The region there of the cochlear nucleus and the
vestibular nuclei, you wouldn't see all if the
cerebellum were there.
So the cerebellum has to be removed to get
this kind of picture.
So now let's look at the part of the cerebellum that's
closely related to the vestibular system.
The vestibulocerebellum.
It's probably the most ancient part of the cerebellum, and
it's somewhat different in its connections from the rest of
the cerebellum.
These parts of the cerebellum have these peculiar names, the
flocculus and the nodulus.
They get direct input from the vestibular nerve.
And they influence muscles of the body axis, as does this
medialmost most of the deep nuclei of the cerebellum,
where all the other outputs of the cerebellum come from.
They come from deep nuclei.
They don't come from the cortex of the cerebellum.
So I just want to show you, here's a diagrammatic top view
of a cerebellum.
Probably based on the cerebellum of a cat, or a rat.
And in the dark red there, and over here in the red dots, you
see the vestibulocerebellum.
or So that's the part that's getting the direct input
there, on the sagittal picture there, it's tucked
under in the back.
The other structure's located medially here in the lighter,
in the pink dots, we refer to as the spinocerebellum,
because it's dominated by input coming
from the spinal cord.
Whereas the hemisphere's the largest part--
in the large animals, anyway--
shown on the small black dots, is getting its input through
the pons coming from [UNINTELLIGIBLE].
So they call that the cerebrocerebellum here.
It's because of that cerebellum has expanded so
much in recent evolution, because with the expansion of
the hemispheres the cerebellum expands along with it.
But primarily in the hemispheres.
And in this picture you see the diagram here of the
primary sensory neurons.
Out here in the inner ear.
And here comes the axon into the hindbrain, through the
eighth nerve.
And note that some of them go directly to that floccular,
nodular cortex of the
cerebellum without any synapse.
So they're secondary sensory neurons of the vestibular
system in that this part of the cerebellum here.
There's also secondary sensory cells there in the vestibular
nuclei that project up to that region of the cerebellum.
So you get both types of inputs to these vestibular
parts of the cerebellum.
And then here we see those regions of the cerebellum
projecting to the vestibular nuclei, just bypassing the
vestigial nucleus.
Bypassing the deep nuclei.
So in these respects, the vestibular parts of the
cerebellum are different from all the rest of the
cerebellum.
Primary sensory neurons reaching them from the
vestibular system, and output cells coming directly from
that cortex to the vestibular nuclei of the hindbrain, and
not going to the deep nuclei here in the cerebellum.
And then those vestibular nuclei, as we mentioned, have
direct projections to the spinal cord.
There's a diagram of it.
Calls it the vestibulospinal pathway, or tract.
And then here, axons of that medial longitudinal fasciculus
that are connecting to the third, fourth, and sixth nerve
nuclei controlling the eye muscles.
This is much too complicated at this point.
I just want to show you here, this diagram of
the cerebellar cortex.
Which is taken from what a frontal section through the
cerebellum would look like.
And they've shown three deep nuclei there.
That's where most of the output, with the exception of
those vestibular system projections, these deep nuclei
receive the output of the cortex of the cerebellum.
And then they project to the rest of the brain.
And this medialmost one not only connects with the
vestibular nuclei, but connects with
the spinal cord also.
Like the vestibular nucleus does.
So does this vestigial nucleus.
It go straight down to the cord of cerebellospinal tract.
It's often called the vestibulospinal tract.
Not to confuse you, just that's the way
neuroanatomists name it.
They name if after the source and the termination.
The other projection of the cerebellum, we'll mention bit
by bit as we go along.
We're not going to put any great emphasis on the
cerebellum except to point out the cerebellum has enlarged as
the hemispheres have enlarged.
And these are just some of the basic connections.
There's a lot of ascending connections that reach the
cortex through the thalamus that we can mention also later
when we talk about cortex.
So we've talked about the locomotor movements.
They're one of the three major types of multipurpose
movements, so let's say a little more now about
orienting the body and head.
Important for reaching the goals of locomotor approach.
We know that early controls were, we call them reflexive
visual inputs reaching neurons that simply, whenever the
input is novel, can trigger reflexive type movements.
I don't think all of them came through the midbrain tectum.
Probably the early ones went through
subthalamus and pretectum.
But that's an understudied area.
Not very much is known about the role
of these other systems.
We'll mention them when we talk about visual systems, but
we know most about the role of the midbrain tectum.
And that's the structure where there's been an evolution of
these topographic representations of the world.
We know the whole retina is represented, it gets direct
inputs from the retina to various parts of the tectum
where there's sort of a map of a retina.
And over the tactal surface, and then there's been an
evolution of auditory maps of the world too, and some other
sensory in the deeper layers of the tectum that precisely
match the visual map.
What do we mean by an auditory map of space?
Well, we can detect space around us by
the source of sounds.
So when we talk about our auditory system, we'll talk a
little bit about how that happens.
Some animals have really good ability to locate by the
source of a sound.
Birds of prey, for example, can do that almost as well as
they can use their vision.
These animals have both very good
vision, very good audition.
They use both of them for localizing prey.
So they can detect, for example, a mouse running on a
forest floor without actually being able to see him, just by
the little sounds that he's making.
Now we know that that tectum gets that input.
That's topographic in the way it
represents the visual world.
That structure, the tectum, can elicit not just orienting
movements but also escape movements.
And they're different kinds of pathways.
The pretectal does similar things.
Non-mammals it's a larger structure.
Relatively smaller in mammals.
We know in mammals it plays a role in protective responses.
It controls contraction of the pupil to bright light.
We know, if there's a rapidly approaching object, it can
elicit avoidance movements.
We also know in some animals where it's been studied well,
and there's some evidence in certain mammals, that the
animal can avoid stationary barriers with mechanisms in
the pretectum.
So that kind of orienting it seems to be important for.
But its role in simple orienting towards novel
objects in the visual field, we know much less about it
because the studies have focused on the tectum.
We talk about the visual grasp reflex, so just like we reach
out and grasp something with our hands, we grasp something
with our fovea, by turning our eyes to directly look at an
object in the visual field.
And the use of electrical stimulation, as well as brain
lesions, have identified these two distinct outputs.
One for escape, and that involves an uncrossed,
descending pathway from the tectum.
And then the cross, tectal's final track, that moves the
head and eyes towards the object.
And we talked a little bit about that already.
I'm mentioning it again now that we're
talking about motor system.
Now, a little more about that third type of
movement, of grasping.
Which can be with the mouth or with the limbs.
So the animal approaches something.
He orients to it.
And he can grasp it either directly with this mouth or by
reaching, and oral grasping is part of the orienting movement
in many animals.
They move their head towards something.
They often move towards it at the same time.
And then, how do they actually grasp it orally?
There are some connections from the tectum to the fifth
nerve nucleus to control the jaws.
But the major control of that movement is not through the
visual system, but through the somatosensory system.
So, for example, a little rodent is bringing the fluid
or whatever he's turning towards
into his whisker field.
And then the somatosensory stimulation
triggers the movement.
That's true for the cat as well, and probably for many
other animals.
But animals that use a less somatic sensation, like a
fish, it's more under the control of vision.
So even after neocortical expansion, these mechanisms
remain important.
The higher controls are there, but both spinal and hindbrain
mechanisms are controlling these orienting and the
grasping movements.
There are also reflex types of controls,
involving somatic sensation.
For example, in a human baby, before he is really able to
control grasping by vision, his endbrain is very immature.
You can actually elicit grasping movements simply by
touching, for example, the back of the hand.
And he will turn the hand and grasp.
And that's partly done by the tactal reflexes, but also by
proprioceptor reflexes.
For example, when his arm is pulled up, he will also grasp
as if he's attempting to hold on to something that causing
his arm to stretch.
So we know there are many levels of control of these
types of movements.
And I'm only going to talk about the
midbrain mechanisms here.
The structure in the midbrain that's most important is the
red nucleus.
It's an interesting nucleus when we do comparative
studies, because it's not there at all in those very
primitive vertebrates, the hagfish and sea lampreys.
These are the primitive jawless vertebrates.
Very few animals in that group that haven't gone extinct.
But they are present in more advanced fish, and in frogs.
And it's pretty prominent in the reptiles, the birds and
the mammals.
Because I emphasize the role of the red nucleus in
grasping, many people have asked me--
because I used to leave this out--
is there a red nucleus all in animals that don't have limbs
and can't grasp?
And the answer is, many of them, yes.
And we know a lot less about its role in these animals.
A little more about comparisons.
If you just take the red nucleus in the midbrain, seen
at the bottom here, we see it's got two major components.
That descending projection that we know is important in
controlling the muscles of the hands and feet, comes from
this large-celled component, which is the caudal component.
So I've indicated that by the blue dots here.
And then the [UNINTELLIGIBLE]
part, of course, is in yellow.
It just has smaller cells.
And I've colored for you here.
Note the change in different animals.
Here, in carnivores, like the cat, the small cell red
nucleus is pretty small.
Most of it's the large cell red nucleus, giving rise to
the rubrospinal spinal tract.
But in monkeys it's like half of it is the
small celled nucleus.
And in apes and humans the small celled nucleus is by far
the dominant.
That small celled component does have connections to
within the red nucleus, but it has important connections that
ascend to the thalamus.
Which means providing information
to the motor cortex.
Because in apes and humans, the motor cortex control has
become the dominant means of controlling
this kind of movement.
One other thing about the rubrospinal projection, in
another kind of comparative study and this is described
there in the [? Streeter ?]
book but I'll go over it right now, was a study of those
neurons in the red nucleus that project
to the spinal cord.
We know they project mainly to the enlargements that control
the limbs, because they're controlling
this kind of movement.
Look at the lower right here initially.
And then let me describe the experiment.
They used retrograde tracers, so here they've injected a
tracer into the lumbar cord.
It's a pretty big injection, so they get all the neurons in
one region of the lumbar cord.
And then they look up in the red nucleus, and they find
neurons that project to the lumbar cord.
By that experimental means.
And they find them distributed through one
part of the red nucleus.
Then they do a similar experiment, and sometimes they
do this with two different retrograde
tracers in the same animal.
They inject the cervical enlargement that controls the
upper lips.
Do the same experiment, and they find where those neurons
are located.
And we see that in the cat they're located in a different
part of the red nucleus.
There was one neuron that actually projected to both
cervical and lumbar enlargements.
Similar experiments were done on the rat, and here we see a
greater intermixing.
The red nucleus has not become so neatly divided into one
part controlling upper limbs and one part
controlling lower limbs.
And there's more of those neurons that projected
[UNINTELLIGIBLE].
If we look at the opossum, it's even more disorganized.
Even though the very same experiment was done in all
these animals.
Same methods, same experiment.
And that kind of change, we see in a number of different
systems when we do comparative studies.
And the usual differences are like this.
That in more recently evolved animals, there's been a great
parcelation, we call it.
Separation of different functional regions.
To talk about somatic motor control, we'll talk about how
the motor neurons in the spinal cord are organized.
First just let's recall that the somatic motor neurons are
just one type of motor system.
We have the autonomic systems, the neuroendocrine systems.
And this is the way they were diagrammed once.
Here's the somatic motor neuron for the synaptic
connection to muscle cells.
Here's the autonomic system, with preganglionic motor
neurons connected to a ganglion cell.
It's in the peripheral nervous system, which then connects to
motor neurons of the autonomic system.
Parasympathetic or sympathetic.
And then we have the neuroendocrine system, where
the neurons in the CNS secrete in the bloodstream.
These are three major kinds of systems.
This is Swanson's diagram of the three motor systems, where
he shows some further subdivisions.
He shows that there's really both small celled and large
celled components of the endocrine secretory system.
Here's the two components of the autonomic nervous system.
It's the different positions of the ganglia.
And then here's the somatic system.
So now what I want to talk about is this system and how
it's organized.
He just shows it as one system here.
First of all, where are the motor neurons located?
This is Swanson's diagram, and we've seen this in the
[? Schmubrain ?] diagrams too.
The motor neurons are located in the ventral horn of the
spinal cord.
Here's the cervical enlargement.
The lumbar enlargement of the cord, where there's more motor
neurons controlling the hands and feet.
And then we get up into the hindbrain, we have these motor
neuron groups that send their axons out through the various
cranial nerves, which are numbered here.
And there the motor neurons are not in a continuous column
all through the hindbrain and midbrain, but they're found in
these separate little nuclei or cell groups.
Those are the motor neurons of the somatic system.
He's left out the motor neurons of the preganglionic
motor neurons of the autonomic system.
And he's left out the endocrine system.
Just the somatic system.
And he's named here the various cranial nerve and
components of these groups of motor neurons.
So now I'm going to show the spinal cord at one of the
enlargements, how the interneurons
are organized there.
And how the descending connections from the brain
relate to those motor neurons.
Which is where I was supposed to start today, but--
First of all if you look at the spinal cord at the
cervical level, there's been--
some medical school texts like to show the organization of
motor neurons there in the ventral horn at the cervical
enlargement this way.
What this is supposed to show is that the motor neurons that
control the axial muscles, nearest the body axis, are
located more immediately.
And the more neurons controlling the most distal
muscles are located most laterally in the core.
The muscles controlling the [UNINTELLIGIBLE] muscles of
the hips and shoulders are in between.
And this comes from a detailed study by a Dutch
neuroanatomist Henricus Kuypers, who did a wonderful
study, published in 1968, of the organization of the
somatic motor system.
He included [UNINTELLIGIBLE]
they did neuroanatomical studies, and Kuypers had been
doing a number of those before this, and then they did a
functional study using lesion method.
And I'm going to go through what they did.
So here's, then, the picture of the cord.
So here you see just a little picture of motor neurons from
medial to lateral.
And he's showing that the distal muscles of the limbs
are located laterally.
Proximal muscles are enervated by the medial motor neurons.
And he also shows that the interneurons here, which he
shows only on the left side here, the interneurons have
the similar [? enrangement. ?]
That is, the lateral interneurons are connecting to
the lateral motor neurons.
So the lateral interneurons are also more concerned with
distal muscles, and the medial interneurons are concerned
with the axial and girdal muscles.
And notice here that he shows a cell, an interneuron here,
that connects to both sides.
Only the interneurons concerned with the axial
muscles do that.
It tends to be a bilateral system.
And just remember the term girdle here refers to control
of the shoulders and hips.
So there's that picture, down below.
And above it he's showing pictures from studies
summarizing studies of the descending
projections from the brain.
First of all, on the left there, he's showing all of the
various studies of corticospinal tract.
He wants to show where, if you just look at all the
corticospinal tract axons, where do they terminate at one
of the cord enlargements?
And he finds out that they terminate throughout the
interneuronal pool on both sides.
But on the opposite side, only to that medial part.
So apparently there's some bilateral projection
controlling the axiom muscles,e but not the more
distal muscles.
And we'll see a functional reason for that in a minute.
Notice also that they go directly into the groups of
motor neurons.
Now, of course, those groups include interneurons too, so
that doesn't prove that they connect
directly with motor neurons.
But separate studies have shown that they indeed do.
There are direct connections to motor neurons, especially
in the higher animals.
Then they separate.
With [? Lorenz ?], he did study separating pathways
coming from the lateral brainstem, the lateral
hindbrain primarily.
Also the midbrain.
They travel laterally through the hindbrain, laterally
through the cord.
They come in through these lateral columns.
And they project in the dorsolateral part of the
interneuronal pool primarily, very few go
to this medial area.
The central medial brainstem pathways that includes the
vestibulospinal, tectospinal and some reticulospinal axons,
they have a contrasting pattern.
They go to this ventral medial position, and they also tend
to go to the opposite side also.
The most medial part of the opposite side.
So the two systems are rather different.
Just by separating the lateral brainstem and the media
brainstem pathways.
This lateral brainstem pathway, much of it comes from
the nucleus [UNINTELLIGIBLE], that red
nucleus in the midbrain.
But, others it is joined by cells in the lateral reticular
formation of the hindbrain as well.
All right.
Now, I'll enlarge these.
I want you to see the overview first here.
First I'm going to show you that the corticospinal
projections, which I show in these diagrams, using a monkey
brain here, and here the embryonic brain that we've
been using, I'm showing the corticospinal projections.
And I've separated the systems for controlling the distal
muscles of the limbs, like the hands, shown
in the solid line.
And the axial muscles.
They come from different parts of the motor cortex here.
And then I separate the lateral brainstem pathways and
the medial brainstem pathways, showing where they originate
and how they travel.
So first, the corticospinal.
We see the body has a topographic representation in
the motor cortex.
What is the motor cortex, again?
How do we define it?
It's the cortex where we can elicit movements by electrical
stimulation with the lowest current.
The tiniest currents.
So with tiny currents through our electrode, that can't
elicit movement from any other parts of the cortex, we can
elicit movements by stimulating the motor cortex.
And that's how it was discovered.
That's how it was defined initially.
It's not that it's the only cortical area where you can
elicit movements.
You can elicit movementts from many different cortical areas.
For example, from the visual cortex, or the
somatosensory cortex.
You can certainly elicit movements from those areas.
But the motor cortex where you can do it is where you can do
it with the tiniest currents.
That's because there are large neurons there in the fifth
layer that send their axons directly to the cord and some
of them even directly to motor neurons.
And we can divide it.
We find the larger areas that represent the distal muscles,
but we also find the rest of the body
muscles represented there.
And I've shown those in the dashed lines.
So the lateral brainstem pathways, I show here coming
from the red nucleus in the midbrain.
And it's a cross-projection, crossed like this.
It's joined by some neurons in the reticular
formation of the hindbrain.
And they project primarily--
not exclusively, but largely to the enlargements.
The cervical enlargement and the lumbar enlargement.
And here in the hindbrain, here's the cross-section in
the midbrain.
And here's where they travel through the hindbrain, in this
lateral position.
The corticospinal axons are down here.
There they are coming through the midbrain through the
cerebral peduncles in the midbrain.
There they are in the pyramidal tracts at the base
of the hindbrain.
The medial brainstem pathways are coming from the optic
tectum, up here in the midbrain.
They only go as far as the cervical cord.
They're coming from vestibular nuclei there,
in the rostral hindbrain.
And many neurons in the medial hindbrain reticular formation
contribute axons also to those descending pathways.
And they travel medially through the cord.
Here they are in the hindbrain, being joined by
axons of these medial neurons.
They travel in that menial
position through the hindbrain.
They travel in the ventromedial columns of the
spinal cord.
And they terminate all the way up and down the cord.
Not just at the enlargements.
And they tend to terminate on both sides, more on the same
side than the other side.
So here was what [? Lorenz ?] and Kuypers did.
They began by eliminating the corticospinal projections.
Why did they do that first?
Well, they tried just eliminating the descending
hindbrain, the pathways that come through the hindbrain.
The lateral pathways and the medial pathways.
And they found that they didn't get much of an effect
as long as the corticospinal tract was still there.
So they reasoned that the corticospinal tract had become
so dominant in these monkeys that they were studying, that
the only way they were going to see the role of these other
pathways was if they eliminated the corticospinal
tract axons first.
So they did what we call a pyramidotomy.
They cut the pyramidal tracts in the hindbrain.
And of course they got some [? diascescus ?]
effects.
Animals got weak.
They had a little trouble moving for a
while, but they recovered.
So they waited for some recovery to occur.
They did get some residual effects.
It's not that the corticospinal tract isn't
doing anything new.
The movements were a little slower, they were a little
weaker, and the monkey couldn't do this.
Couldn't do that anymore.
He could only do that.
So the monkeys could still function pretty well.
But they lacked some of the finesse of the animals with
corticospinal tracts.
So then they worked with those monkeys that had the
pyramidotomy.
And then they did either this leson or that lesion.
They eliminated one or the other of those pathways from
the hindbrain.
Now, remember the medial pathways tend
to go to both sides.
And if they made that lesion on just one side, they didn't
get much of an effect.
So that lesion, they had to get both sides.
The lateral pathways tend to stay on one side, so that one
they could usually do just on one side.
And they could compare the two hands.
So here's their lesions.
First pyramidotomy, and they were doing it up
there in the hindbrain.
When the pyramidal track travels right along the base
of the hindbrain.
I've done this legion also in hamsters to be able to compare
with the monkey results.
Here you see the lesion where it was in the hindbrain, and
it goes across the midline, it gets both sides.
Both pyramidal tracts.
And then they allowed recovery from that lesion.
Then they added the second lesion.
And what they did is expose the base of
the hindbrain again.
Same way they had done for the pyramidal tract lesion.
But now they inserted a knife that went
up along the midline.
But left all the lateral pathways intact.
They cut all those medial traveling
axons, as I show here.
And they observed what happened.
Other animals, they added a lesion of the lateral pathways
making it at the hindbrain level.
Here's a cross-section of the hindbrain.
They went in there with an electrode and burned a lesion,
burned an area out, eliminating the rubrospinal
tract and many of those other axons.
So that was the logic they were following.
So, what happened?
With the pyramidotomy, loss of speed and strength and loss of
control of the digits used one at a time.
They had a little food board, with little cups.
Large cups, small cups, with tiny bits of food in the small
ones and larger bits of food in the large cups.
And they just looked at what the monkey could do.
I have a film of this, I wish we had time to show the film.
It's a very nice film and you see these
defects in the monkey.
But the monkey with the pyramidal tract lesion could
get all the larger bits of food and the larger cups out
using his whole hand.
But he couldn't get the little bits that he needed to his
oppositional thumb and the single fingers.
So that remained lost with the pyramidal tract lesion.
So now those pyramidotomized monkeys, some of them had a
destruction of the medial pathways.
When you first see these monkeys, it looks really bad.
The monkey's just lying there.
He can't even right himself.
So in fact, it took them about some of them up to 40 days
before they could right themselves.
How could they ever right themselves?
They're missing all the pathways from
the vestibular nuclei.
Well, they have somatosensory inputs coming in through their
limbs, through their touch system.
And they gradually reacquired the kind of movement that
those inputs caused.
And they regained the ability to right themselves.
But it shows the dominance of the vestibular system for this
kind of movement.
They didn't really have the normal corrective movements
when they would be falling, as you expect without the
vestibular system.
They walked in a really odd way.
They could recover pretty good walking, although it was not
good at all at the first.
But they didn't seem to be able to orient normally.
They would be walking towards some food there, and they
would wander off to the side.
They seemed very unable to direct their
movements towards a goal.
It was very dramatic, these effects.
So did they seem really helpless?
Yes.
But, you strap them in a chair where they don't have to
control their axial muscles.
You strap them in a chair and give them use of their hands.
Now, they had a little trouble extending.
But if you brought the food close enough, they could reach
out and they could make this movement and they could pick
up the food.
So they definitely had some movement control.
They couldn't control their axial muscles as well, but
they could control those distal muscles.
They had those pathways.
As the anatomical studies had predicted, they should still
have, after that lesion.
So distal control was much better than axial control.
If they did the lateral brainstem pathway lesion
instead, and they did this only on one side, now it was
very interesting.
They sat them, strapped them in the chair.
One of the hands could reach and grasp quite readily.
The other hand would start to reach but
couldn't grasp the object.
And it seemed very odd because if you let the monkey go, let
him run around the lab, he could climb the cage using
both hands, as long as he was doing locomotive movements and
whole body movements, they called them, he
could control the hands.
But you put him in a chair and you're asking him to just
control that one hand in a grasping movement,
he couldn't do it.
That tells you something about the nature of paralysis.
You can be paralyzed for one use of the muscles in one
situation, and not in other situations.
It depends on the movement and how it's organized in the
central nervous system.
I just want to mention here that the people that have lost
their tetraplegics, sometimes we say quadriplegics, when the
like to combine the Latin and the Greek.
I like the one just from the Greek, tetraplegic, complete
losing ability to move all four limbs.
If those people, you ask them to just think about doing
something, you do activate parts of the motor cortex.
And here they're showing, when they asked them to move their
lips, of course the lips weren't moving, but they were
imagining moving their lips.
They felt they were moving their lips.
They activated that part of the motor cortex.
Similarly, for one hand or the other hand, one arm
and the other arm.
So they still have an organized motor cortex.
So we know if we had a way to get those long pathways
reconnected, or are some other way to use that activity of
the brain, we should be able to get those people to move
again, and various people working on new prosthetic
devices are trying to