This is going to be... Let me clear everything
out. I don't know why. This is going to be visual
inputs but only the retina to the superior colliculus
because only the mesencephalon. Remember the
three issues that I have with the mesencephalon
with the autistic phenotype. Eye movements because
of the superior colliculus. This is a fast relay
station and hearing, audit, audition. which is
the inferior colliculus remember auditory brainstem
response wave five which is the last wave up
until it gets hearing gets into the subcortical
areas like the thalamus and so forth and then
motor movements with the basal ganglia we'll
touch a little bit about the basal ganglia here
because of the superior colliculus projecting
to the basal ganglia for motor movements. So
this is the same kind of diagram cartoon, if
you will, from the auditory brainstem response
episode, the whiteboard. So the green is the
inferior colliculus, which is in the mesencephalon.
The red is the superior colliculus, which is
this, right here. And then this is the thalamus,
okay, both. So contralateral, which means both
sides. These little humps are the medial, geniculate.
And then the lateral geniculate, medial is in
the middle, lateral is on the outside. This is
vision. This is vision. And this is auditory,
here. Remember in the Autism and Eye Movements
episode, I said that these things are spatially
close. They can just reach out and high -five
each other. It's for fast transmission. So, if
we think about the retina, okay? I always like
to draw the retina thick and dark because of
the melanin. And then we have the pupil, okay?
This is just... the eye right here pretty good
it's a pretty good eye and then there's a monosynaptic
connection not only to the thalamus here the
lateral geniculate which is here it's just a
different angle and the medial but of course
the retina projects to the thalamus monosynaptically
you know one connection but also to the superior
colliculus which is like this you're just like
a noodle if this was the mesencephalon okay and
then this is just kind of like the pons the brain
stem okay sometimes i draw this connection to
the lateral geniculate which is the relay station
for all vision two i want to do green for the
projections two lateral geniculate to the superior
caliculus, which is right here. I might as well
color coat these. The red's got black. Is it
showing up red? Not really. Okay, I gotta work
on this. And then the inferior caliculus, okay?
But there's about 15 % of nerve fibers that go
directly to the superior caliculus, okay? This
is for fast acting visual responses, okay? So
we can orient our gaze and orient our head movements
okay because we're going to get into some of
these descending fibers so about 15 percent are
retina to superior colliculus of the total fibers
which is still millions of fibers okay the rest
of them go to the lateral geniculate all right
so some of these fibers from the superior colliculus
five minutes already are descending Okay, so
they go down here to the to the rest of the brain
stem some of these are cranial nerves three four
and six specifically cranial nerve three and
four are within the mesencephalon ocular motor
and tracheal cranial nerve, okay, this is for
eye movements and then Cranial nerve six is down
below the mesencephalon a bit which is abducens.
If you know anything about the cranial nerves,
cranial nerve six is the easy one, abducens.
It's because the eyes are independent structures,
but they orient identically. Like their movements
are identical, you know, however the eyes are
doing. It's just, that's cranial nerve six. And
then The superior colliculus will also touch
9, 10, 11, and 12 as well to help orient the
head towards wherever we want to send our vision
or visual inputs. Now 10 is the easy one. The
vagus nerve, that's the big one. So this is the
thalamus. Now that I think about it, I don't
know if we ever drew out the thalamus like we
should. Probably. Because we talk about it a
lot. We talk about the thalamic reticular nucleus,
TRN, the shell that kind of protects the thalamus
here. Thalamus is pretty big. It's a workhorse.
If we would just draw the thalamus out here,
let's just say it's like this angle, medial geniculate
right here, and then the lateral geniculate.
right here okay if we were going to draw and
just imagine this is cut out okay this is just
like a shell okay this is let's just say this
is the trn this is protecting the thalamus let's
just say this is the rest of the thalamus but
it's just cut out and there's a strong nuclei
here called pulvin here which is uh receiving
a lot of sensory inputs okay and The thalamus
has a lot of little subdivisions. Okay, so this
shell is all inhibition. Remember the thalamic
reticular nucleus inhibitory neurons and autism
episode, all about inhibition. A lot of parvalbium
here and somatostatin, which are kind of the
top two inhibition neurons. Parvoalbum interneuron
is fast acting, GABA -A a lot, and some GABA
-C. And then somatostatin is more slower acting,
GABA -B. So GABA -A is anywhere from like 2 to
10 milliseconds of activation. GABA -B is 10
to 50 milliseconds, so it's kind of delayed.
Okay, so this thalamus here, I guess we could
draw it out here too. has a shell over it it's
like a security guard okay if you if you're looking
at this from the overhead view this view right
here it's just kind of like from the posterior
but kind of angled it's kind of angled down just
so we can see it but if you're going directly
overhead looking at it like this you can say
that the thalamus it's kind of like two eggs
or something like this the thalamic reticular
nucleus is on the outside. This prevents unwanted
projections coming in because the thalamus receives
all sensory information at least the thalamic
reticular nucleus does and this will filter out
what can enter because the thalamus is a workhorse
okay so all sensations Okay, for instance, vision,
the lateral geniculate here or here, the auditory
auditory comes more this way from the ears, of
course, and then in inward to the brainstem and
then up. Okay, and then like mechanical receptors,
mechanical receptors, touch from the peripheral.
will come in through the spine and up the brain
stem and into the thalamus like this. Okay? So
I guess back to the superior colliculus but here's
um since we haven't really discussed the thalamus
in detail not uh we haven't really visualized
it okay so this shell right here is very protective
with good measure too good it's it's needed Just
imagine sensing or perceiving all senses coming
in. It would be wild. It's almost like schizophrenia
does this with the delusions. They can't discriminate
all the senses. And, you know, autism is very
close, very close to schizophrenia. So the superior
colliculus here, it receives about 15 % of the
vision nerve fibers directly. So what are some
of the outputs? Let's just say the superior colliculus
receives some visual information. What happens
next? Okay, there's a little crosstalk that it
will speak within itself, and this happens fast
for autism. compared to typicals. The inputs
going across and enter superior colliculus and
even from side to side, contralateral. With autism,
it's fast, much faster than typicals. But one
of the key areas that I've talked about, and
it will be up here, the frontal eye fields. We
have like a supplementary frontal eye fields
up here and then I should just maybe write F
E F F E F for frontal eye fields this is right
in here so vision superior colliculus and um
deep inside the brain deep inside right in the
middle all the way back up to the frontal eye
fields however it will hit the thalamus first
This isn't superior colliculus to frontal eye
fields of monosynaptic connection. Okay, sometimes
I draw it out as such, but here in the thalamus
is the pulmonary that I mentioned. And then there
is this track up here. You could say that it's
here. So pulmonary here is also here. And then
the medial, medial dorsal, MD thalamus, MD thalamus,
medial dorsal. And this is also here. So here.
So, retina to the superior colliculus, superior
colliculus to the pulmonary, pulmonary to the
medial dorsal, to the fertile eye fields. And
this is a fast -acting connection here with the
autistic phenotype because the relay of stimuli
into this superior colliculus and out of it is
really fast for autism. Okay. And this is a big
connection. So we'll go all the way up to here.
The frontal eye fields will kind of help coordinate
some motor movements because this is a part of
the sensory motor region, which is here. Okay.
And then on this backside, it's kind of angled.
It's angled. It's a somatosensory. S1 cortex
and then the superior colliculus will also because
this is the occipital lobe here V1 through V4
will happen maybe even V5 so Remember, we're
just talking about the superior colliculus. Superior
colliculus will speak back and forth to visual
cortex one as well. It's kind of giving it updates.
And this is happening fast as well. Okay, so
let's see here. Something that I haven't mentioned
so far is, I have mentioned it in previous episodes
though, is the waves. A lot of alpha. Beta gamma
Low and high gamma. So this is 30 to 80 Hertz
80 plus 12 to 30 Hertz 8 to 12 a lot of this
happening in these earliest centuries is Here
for autism autism versus here for typical With
a little spike into low gamma to help kind of
modulate and task switch orient the vision but
autistics live here okay so this connection here
is twice as fast nearly twice as fast so from
retina, superior colliculus, pulmonary, radial
dorsal to frontal eye fields this is happening
at around let's see anywhere from 55 to 80 milliseconds.
Show up kind of sloppy compared to around 80
to 100 milliseconds for the autistic phenotype
or for atypicals. It doesn't seem like much but
that is a lot. But then the frontal eye fields
will speak back down to the thalamus and also
the superior colliculus and this connection back
down is slow and this hurts the eye gaze and
eye contact and so forth and modulating eye attention
okay the superior colliculus will also talk to
the basal ganglia the basal ganglia are Five,
if we would look at these from the back side
because it's just going to be easier to see.
So we have the thalamus and then we have the
caudate nucleus up through here. The caudate
nucleus is attached to the putamen. We can just
say this and the globus pallidus external and
internal. Globus pallidus external and internal
make kind of a, it's hard to see, makes a triangle.
And then below the thalamus is a subthalamic
nucleus, okay? And the superior colliculus will
be, let's say, here. And then the substantia
nigra here, pars reticulata for the GABA and
pars compacta for the dopamine. The superior
colliculus will speak to the substantia nigra
reticulata and the globus pallidus internal.
Here. It's modulating motor movements. So the
inputs coming out of the superior colliculus
are happening faster. The information coming
back down to the superior colliculus is delayed.
So afferents are heightened. Fast. Efferents
are delayed. with the superior colliculus. And
this is hurting vision. It's hurting eye movements,
saccades. They're called saccades. The eye movements
are called saccades. And this is hurting. So
we just draw out the brain here. You know, this
is the prefrontal cortex here. And then it goes
up the parietal lobe. Parietal lobe. is here,
and the superior colliculus will also speak up
to here, but mostly the somatosensory cortex
here. And then this is the occipital in the back.
So V1 to V5. But I only want to talk about superior
colliculus, not the rest of the eye inputs, not
the rest of the eyes. just because we can hit
this mesencephalon. But the big thing here is
heightened activity out of the superior colliculus
and delayed inputs coming back down. This is
a feed forward feedback type of movements here
so that we can have attention to the outside
world. Remember the mesencephalon has three main
goals here. Sensory integration, right? This
is easy now. A bunch of sensory is happening
throughout this mesencephalon. A lot of sensory
connections. Touch, hearing, auditory, vision
coming this way, and then speaking to the thalamus.
There's a close connection here with the thalamus.
So it's like a feedback loop. And also the cerebellum.
cerebellums here with the um purgenji cells lots
of purgenji cells here which are all inhibitory
and it's kind of shutting off unwanted movements
noise if you will the second row is the motor
movements and that's going to be in large part
not necessarily the eyes but with this basal
ganglia this is the basal ganglia from the backside
and then orienting attention to the outside world.
It's the mesencephalon. Fast acting in and out
to orient the attention and then slow acting
back to back to the mesencephalon for eye movements.
So there are a lot of delays happening. This
is the superior colliculus. It's a relay station
for vision and it's very fast acting stuff. especially
with the autistic phenotype because there's a
lot of gamma waves compared to alpha and beta
and sometimes they're even coupled there's this
thing called theta gamma coupling or alpha theta
coupling this is four to eight this is helping
smooth task switching is what theta is doing
with this background theta So gamma is what's
activated, the circuitry, the neural correlates
activating, and then theta is kind of scanning
all this background noise to help modulate it.
So the superior colloculus is one of the fascinating
brain region. Remember in the barn owls, it's
called optic tectum because the mesencephalon
can be broken down into three areas. Tectum and
tecmitum or two of the three. The third one is
Cerebral Prudential. I don't know what that is,
to be honest, but the mesencephalon is very fast
acting relay station. It's very small and I think
that's why it doesn't subdivide because these
three crucial, these are three crucial rows of
the mesencephalon. So evolution says no more.
It has to be on point. has to be fully developed
because it needs to be because the living organism
remember the role of the central nervous system
is to move the living organism and in large part
these three things is it this is it for the living
organism the the biggest roles here don't you
think it's fascinating that the mesencephalon
which is just right here it's called the midbrain
This is called the midbrain, but if the bottom
of the brainstem is here and the top of the cortex
is here, in no way is that in the middle. All
of this stuff that came later is just kind of
helping and hurting the human because there's
too much here. This is too powerful. Mesencephalon
superior colliculus eye movements.