Welcome to part 3 of Sci’s basic posts on Neuroanatomy, part of Back to Basics week!
Apparently everyone is very impressed by how hot my brain is (see parts one and two), but unfortunately, we’re almost out of pics. Today we’re covering the rest of the bits of my brain that look really awesome, which really boils down to all the ones you wouldn’t be able to see if you were just looking at the outside. And it turns out that Sci has a LOVELY basal ganglia. She is thrilled by this, the basal ganglia is her favoritest part of the brain.
First, a note: those cross-hairs that you’ve been seeing all the time are features of the analysis program, apparently, and can’t get taken out. Blah. But we shall forge ahead!
This is a picture of just how lovely Sci’s basal ganglia is. You can’t see the whole of it, of course, it’s a lot of 3-D. But what you CAN see is here:
Outlined above in green is two things:
1) Abundant evidence that Sci cannot draw with her laptop mouse
In the picture above, the blue parts are the ventricular system, while the green part lining the lateral parts of the ventricular system is your caudate.
The problem with neuroanatomy is that you end up having to rotate a lot of things in your head. With the picture of MY brain above, you have to picture looking straight down at the top of my head, and you’re at about the level of where my ears join my skull. Ish.
Anyway, the caudate is a very important part of the brain to Sci, because it’s freakin’ covered in dopamine terminals. As we know, dopamine is involved in motor stuff, as well as in what we neuro-geeks like to call the “salience of stimuli”. The caudate is heavility involved in the salience of stimuli, which is basically a way to say how much attention your brain pays to a given stimulus compared to background stimuli. A stimulus like, say, cocaine, has a hell of a lot of salience. The caudate in particular is involved in the learning and memory aspects of the salience of stimuli. The caudate may also be dysfunctional in individuals with OCD.
So, going back to that picture, you can also see, this time outlined in pink, my putamen. It is separated from the caudate by this stripy pit of white matter called the anterior limb of the internal capsule, which is a whole bunch of myelinated neurons going down from the cortex to the spinal cord, carrying things like motor commands and sensory modulation.
*NOTE: When you hear talk of things like your grey matter, what you’re hearing about is some nekkid neurons. White matter, on the other hand, is made of the fiber tracts of neurons, wrapped in myelin. Myelin is an outgrowth of glial cells, which wraps around the axon in layers, insulating it and allowing signals to bounce along much faster than they would normally (I should really blog about myelin sometime…). Thus, myelin is generally found in the brain when you’re looking at fiber tracts heading to various places.
Anyway, the putamen performs many functions that are connected with the caudate, and in fact in rodents, these two areas are fused together to make the caudate-putamen. The putamen helps with caudate in learning related to the salience of stimuli, but also does a certain amount of work in movement. It, like the caudate and the rest of the basal ganglia, is ALSO full of dopamine, and is therefore awesome.
OOOOH! I just looked at that again and realized that you can see my globus pallidus on that slide!!! Here:
Sweeeeet. The globus pallidus, meaning “pale body“, is one of the most important parts of the basal ganglia. The basal ganglia pretty much forms its own little loop of modulation, taking in information on salience, movement, and other cotical stuff, processing it, and sending it back up to the cortex via the thalamus (which we’ll get to). But to do that, everything coming in or out has to get past the bouncer: the globus pallidus. It’s the first stop in and the last stop out in the two loops going through the basal ganglia. These two loops are extremely important, and are known as direct and indirect. Scientists are very interested in the modulations of those groups when looking at diseases such as Parkinson’s, with appears to involve too much power given to the indirect loop, and too little to the direct loop (though there are a LOT of other things that Parkinson’s involves. There’s some crazy stuff that may be out there involving neuronal firing and oscillation…). I can try and explain this some other time, maybe…I should also devote an entire post (or two) to just an explanation of the basal ganglia. Sigh…so much to blog, so little time.
There is another, very big thing which EVERYONE needs to see on this slide:
That. That is the thalamus. And if you know ANY part of your brain and know it’s important, know the thalamus. Frontal cortex wouldn’t get along at all without this. It’s like two little eggs right off your midline. Almost everything coming up or down, whether it’s from the brain to the body, or the body to the brain, goes through the thalamus, and in some cases where things are getting processed, a specific signal may go through the thalamus several times. Basically, it’s a relay, but it’s one darn important relay.
This next picture here I think is really lovely. Not because there’s TOO much to see in it, but because it really gives you a lovely idea of the way the white matter flows. You can see the tracts of white matter flowing out the cortex and down to the brain stem, where they will head out to the spinal cord (or in some cases going the other way, from spinal cord to cortex).
Finally, there’s this picture here:
This is taken looking straight down at the top of my head, about the level of the bridge of my nose. You can see several things right off the bat. First off, you can see my EYES! Looks very freaky. You can actually see a good bit of detail, including the lens at the front, and the fact that the entire middle is blank and full of fluid. You can also see the cartilage in Sci’s nose and the fact that her sinuses were remarkably clear that day.
But what I really like about this is the bottom of the picture, for there, in all its glory, is my cerebellum. To me, this picture brings out what’s so nice about the cerebellum. You can see the midline, the even striations (stripes) on either side. That even-ness and similarity is reflected in the way the cerebellum operates. All information comes in the same way, is processed in the same sequence, and is sent out the same way. Yet for all that, the cerebellum does a vast array of mind-bogglingly complex stuff. It’s the art of the brain, simple, but so crazy complex. Gorgeous.
I was really hoping you could make out my substantia nigra here, but I think we’re too high still. Next time.
Ohoh! One more thing.
Many people know that their brain is divided into two halves, and I’m sure the question must have occurred to some of you, do these two halves act indenpendantly, or do they communicate.
Absolutely they communicate, and that thing there outlined in orange does it all. That area is a huge mass of white matter known as the corpus callosum, and it helps the two halves of the brain communicate, and joins them together. Interestingly, you can live WITHOUT that connection, as sometimes happens when you have a patient with reallybad epilepsy. You can actually cut the corpus callosum, and it will sometimes help with the seizures, though it’s definitely not the first thing you’d think of doing.
But that’s about all I’ve got! Don’t I have a pretty brain?! Of course, brains vary a great deal in shape (you may notice that my right lateral ventricle is larger than my left, and that I have a certain gap in my medial parietal lobe), but the general features remain the same. And now you can see some of the features of the great organ that controls it all. Makes you want to be a neuroscientist, don’t it?