the diencephalon is all things thalamus and it's part of that deep gray matter that
exists within the brain in this image we can see our diencephalon right here it includes
the dorsal thalamus which is this part and the hypothalamus which is this part and you
can see that it's continuous with the midbrain of the brainstem so again here's our medulla
oblongata and our ponds and our midbrain the ventral thalamus is off the midline and so
we can't see it in this image the epithalamus includes the pineal gland and the habenula
and again they're not really very visible in this particular brain section and we just don't have
time to talk about everything so we're going to put the epithalamus on the back burner so
within the diencephalon we're going to today we're going to talk about the dorsal thalamus
and the hypothalamus the dorsal thalamus is this area of the brain here and here it's
bilateral it's connected you have to thalamic hemispheres connected by a massa intermedia
and the Massa intermedia is simply a lump of brain tissue brain cells neurons that connect
the two halves of the thalamus we're not going to talk about all 40 nuclei that exists within
the dorsal thalamus we're going to lump them into big functional groups so the big functional groups
of the thalamus are it participates in the motor system with the basal nuclei so Globus
pallidus and putamen and caudate are all going to participate with parts of the dorsal thalamus in
that big basal ganglia basal nuclei behavioral pattern motor patterns it also participates in
the limbic system certain limbic relays are going to go through that the dorsal thalamus
and most importantly the the dorsal thalamus is the gateway to your senses all of your senses
with the exception of olfaction are going to go through the dorsal thalamus before they get to
cortex I first want to talk about the sensory nuclei so if this is our dorsal thalamus here
what I failed to mention in the last slide is there's an inter inter medullary lamina so inter
medullary lamina and that's just represented here by this gray line and it's it's um it's
kind of like it's all the fiber tracts that run within the thalamus to make all of the
intra dynamic connections so it they kind of coalesce into this band of fibers that you can
see two really important nuclei that I want to point out so if this is our midline this
is our medial geniculate here and our lateral geniculate over here the medial geniculate is
where all of the information from cranial nerve eight the vestibular cochlear nerve
goes through the brainstem and then all that information from the cochlea goes
to the medial geniculate nucleus before it goes to areas 41 and 42 of the temporal lobe
the lateral geniculate nucleus here receives information from the retina and information
from the retina goes straight through the optic nerve to the LGN and then up to area 18 or I'm
sorry area 17 which is primary visual cortex and that of course is in your occipital lobe
when it comes to other somatosensory information remember that our ALS system our anterolateral
system is carrying gross touch and pain and it travels in parallel with the dorsal column
or medial lemniscus system which is fine touch okay all of this information goes into an area
called the ventral posterior nucleus now there are two subdivisions - the ventral posterior nucleus
there's a medial and it is getting somatosensory information from above the neck so what does that
mean that's cranial nerve five remember cranial nerve five is sensory for the oral cavity and
the face so the cranial nerve five comes into the brainstem it's information goes into the
ventral posterior nucleus the medial aspect of it before it goes up to areas three one and two
which is that primary somatosensory cortex below the neck our ALS and gross touch our ALS system
with gross tension pain our medial lemniscus system for fine touch is going to come up and
again synapse in the ventral posterior nucleus but in the lateral aspect so VP the ventral
posterior lateral is somatosensory below the neck and I apologize for the fact that all
of these silly nuclei within the diencephalon within the especially within the thalamus are
named so weird ventral posterior medial ventral posterior lateral that it's complicated and it
makes it a lot harder to learn but I'm not going to ask you to memorize every single nucleus so
if you abbreviate it V P M above the neck V P L below the neck you'll have the two nuclei or the
the nuclei on at some division where all of the sensory information goes through before it goes to
cortex in the next segment we'll talk about motor and limbic connections of the dorsal thalamus