Where is the thalamus?


I've been talking about the Alamos this

week does that ring any bells with you


nuru Anatomy right let me show them this

kept it more lighting so the thalamus

where is the thalamus and what does the

thalamus do it's difficult well maybe

it's not difficult getting thoose est

bellyful of us but it's difficult to

talk about the thalamus for too long

because too much detail but since I

talked about it this week and it's

something we've been building up to with

our neuroanatomy in the medicine program

here I thought I'd recap it here I think

the important things about the thalamus

are you should be able to find it and

you're going to be looking at brains

I imagine on M R and CT scans of the

head right so we should have a look and

see how you can find the thalamus in

relation to other structures within the

cranial cavity in the brain right so

where is the thalamus how do you find it

if we look at it from different

perspectives improve it what's nearby

and then what does the thalamus do maybe

we should turn it around maybe we should

just do what the thalamus does now and

then go and find it as that same yeah

right the thalamus then so the thalamus

is often considered briefly a sensory

sieve all right so it's it forms in the

embryo in the dying careful on so if the

TN kept healing careful on forms the

cerebrum the diencephalon forms of stuff

in the middle what this means is that

it's between the higher centers of the

brain and the spinal cord which means

it's likely that an awful lot of stuff

goes through the thalamus between the

brain and the spinal cord

right now the stretches and indeed

that's what we see so consider

you are an organism covered in a huge

amount of sensory apparatus just think

about how many sensory nerves you have

on a patch of skin on your body then

think about how much skin you have on

your body right now you're not thinking

about your little finger all the time

but you probably are thinking and you

can probably feel the little finger on

your right hand now that I've mentioned

it right so all that sensory information

is available to you but you're not aware

of it all the time as soon as a fly

lands on your on you're instantly aware

of that fly on your arm and you're

probably brushing it off right

that's the thalamus doing that so the

thalamus is receiving all of this

sensory information from the body and

it's discarding most of it most of it is

so it's not important it's not

interesting but as soon as a fly lands

in your arm it says that that's

interesting and it raises that sensory

information to a higher level so it goes

to your somatosensory cortex to your

cerebrum your consciousness is now aware

of the fly on the skin there but you

know the breeze the changing temperature

all those other things that the sensory

apparatus in our skin is detecting

you're not really aware of your brain is

not the the thalamus chooses not to send

that on right and it's more than that

the thalamus is also receiving sensory

information from vision so it has you've

may have heard of the lateral geniculate

nucleus in the in the visual pathway

right so you've got your optic nerve

goes through the optic chiasm becomes

the optic tracts goes to the lateral

geniculate nucleus goes through the

thalamus that's hanging off the thalamus

and into the visual cortex at the back

that's it's also passing this sensory

information on and it's also linked to

the is in the inferior colliculi of the

midbrain so auditory information that's

coming in is also passing through the

medial geniculate nucleus of the

thalamus then going on to auditory

sensors so it's it's it's receiving all

sorts of sensory information and

filtering and passing and doing magical

things with it it also receives taste

it's receiving all the spinothalamic

tracks were these dorsal columns of our

spinal cords they're all going to the

thalamus and then there's another sign

apps and

the connection with the third neuron

after the cerebrum the one sense that it

doesn't receive as far as I'm aware is

smell the olfactory nerves cranial

nerves wanna direct extensions of the

cerebral cortex it seems so that sensory

information goes straight back into the

brain doesn't go anywhere near the

thalamus but otherwise the thalamus is

it receives all the sensory information

and decides whether it's useful or

relevant or not maybe the cranial nerves

so trigeminal nerve cranial no 5 the

major sensory nerve of the face that

sends its information back into the

thalamus so you can imagine then that a

lesion and injury to the thalamus on one

side is likely to cause a loss of

sensation from the other side of the

body depending upon which part of the

phallus much maybe being injured but

it's a little bit more complicated than

that because as we look at the thalamus

and we look at the wiring we look at the

connections to it we see it's also

connected to the cerebellum it's also

connected to the basal ganglia and those

are involved in movement right in the

initiation of movement in the storage of

sequences of movements your handwriting

is stored in your cerebellum here your

signature is there your dance moves are

all stored in the cerebellum all that

sort of stuff and the basal ganglia is

so important in the initiation

initiation of movement and and the

coordination of movements these things

are linked up to the cerebellum as well

which maybe isn't too surprising if you

think about how we need all that

proprioceptive information all that

sensory information to work with the

motor information so that we can make

these seemingly simple movements which

are in fact incredibly complicated as

I'm moving my arms around I'm shifting

my balance as some muscles are

contracting other muscles got to relax

all that sort of stuff but then when we

look further at the thalamus we see that

is also connected to the limbic system

the limbic system is involved in memory

emotion things like that the hippocampus

is part of the limbic system and

famously that gets a large or in black

cab drivers so taxi drivers in London if

you look at their hippocampus once

they've done the knowledge was they've

learned all the streets of London their

hippocampus is get bigger it's a memory

and spatial awareness and emotional that

sort of thing is also linked to the


maybe the triggering of memories through

vision or the the storage of visual


so obviously memories are what we

perceive so we make sense that the

sensory information that goes in to us

may well pass through the thalamus and

be linked to the limbic system in terms

of memory storage of course pain is a

sense that goes through the thalamus and

pain has an emotional context to it so

maybe there's that linking there between

the limbic system and emotion and pain

coming in through the thalamus anyway

there's a lot going on with the thalamus

also it seems that there are loops

between the thalamus and the cortex and

the cortex doesn't act in isolation it

includes the thalamus in some of these

other processing functions so the

thalamus is very central there's a lot

going on there it's very important so in

fact if somebody has a lesion to their

plan emotional injury it may well not be

as simple as a change in in sensory

information a change in sensation they

may will also experience other other

problems motor function problems and

general behavior changes so the phallus

hopefully the point I've got across is

really important and really useful so

where is it that's what you want to know

right there all right you didn't see

that okay it's it's here so here's a

midsagittal section of the head here is

the do you just like to see this you can

see the cerebral cortex here this is the

middle cerebral artery coming around

here here's the nasal cavity frontal

sinus sphenoid sinus there's the

pituitary gland up here here comes the

spinal cord into the medulla oblongata

the pons the midbrain across here

here's the corpus callosum up here so

this is the thumbless

that's where you find it I don't know if

you can see but it's a little space it's

an ovoid shape and there's a thalamus on

either side so where they meet they have

this into thalamic adhesion it's

doubtful whether there are any neurons

crossing from side to side that ever

there might be okay this is the

hypothalamus down here and there's a

space here then between the left and

right sides and that space is the third

ventricle of the ventricular system so

the third ventricle and we have the

cerebral aqueduct down here

and there's the fourth ventricle in

there and this is the cerebellum so

that's where the thalamus is it's very

central and there are two one on either

side the information from the spinal

cord comes up and from other parts of

the body goes into the thalamus then

there are a number of connections with a

number of other structures so the

thalamus is just lateral to the midline

if we get another view so then here are

the lateral ventricles here and here if

we slice again we see the lateral

ventricles but they're being cut and now

here we see the thalamus on either side

so you can see how it's an ovoid shape

slice again and here we go so now you

can see most of the thalamus you can see

that ovoid structure in the midline here

we have the third ventricle that little

slit space and here we have the basal

ganglia of the Globus pallidus and the

putin the lenticular or the lenta form

nucleus that this is the thalamus here

which was very much in the middle

and as we slice again then we're through

to the midbrain that's good okay so now

you know where the thalamus is and you

know what it does pretty much okay so

the thalamus is important and you know

how to find it

let's have a look on some radiographs

now let's have a look on some of em our

images and see where the thalamus is

from different perspectives okay so the

feminists from a transverse section the

thalamus in a sagittal section mid

sagittal section

well ich and the thalamus from a coronal

section so can you see the the space is

there of the lateral ventricles they're

always good landmarks aren't they

looking at em our images okay a little

bit of neuroanatomy hopefully that

wasn't too painful I'm just a little

focused on a particular structure within

the brain hopefully you know a little

bit more about it I don't know if we'll

be doing any more neuroanatomy next time

how do you feel about neural Anatomy

it's very difficult to do with models

for one thing a lot of is very easy so

tarik but there you go

anyway okay see you next time