Back to Basics 2: Neuroanatomy. Let's get started.

Aug 24 2010 Published by under Basic Science Posts, Neuroanatomy

As part of my Back to Basics week, one thing you'll want is an introduction to NEUROANATOMY. The brain ain't just a pile of unorganized grey matter, no indeed. In fact, it's really highly organized. Let's get started.

Some of you may recall that I got my brain scanned in an MRI for the sake of science. Well, my lovely fellow grad student was nice enough to send me some of my baseline pictures! I think I have a lovely brain (see my profile pic? I'm totally hot, right?), and so I thought I would share some of it with you. Besides, I blog a lot about basic (and not so basic) neuroanatomy, and so we can use hot pics of Sci's brain to give you some insight into areas of the brain that are popular in science today.

And just to scratch the surface:
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I'll be dividing these posts into three parts, the first with general features and terms, and the second and third for some of the interior features that happened to come out really well on my scan.

First off, a couple of things on slicing and viewing, and then we'll get to the pictures. There are generally three ways in which a brain is "sliced". This can be literal slicing (Sci got to prep brains for her neuroanatomy class with a brain knife once, it was AWESOME), or metaphorical slicing, in which images taken of the brain's anatomy are oriented in certain ways to make it obvious what you're looking at. Generally, there are three basic ways of slicing.

Coronal section: These slices go from the front of the brain to the back. If you think of the brain as a loaf of bread, that's how you'd be slicing it.

Sagittal section: Usually what you will see here is a mid-sagittal section, where the brain is sliced in half right down the middle of your nose. To continue with carb-infused metaphors, the way a hotdog bun is sliced.

Horizontal section: These slices can also be referred to as 'transverse', and slice the brain in flat slices from front to back, like you would slice a hamburger bun.

There are also a couple of other directional terms that will be very useful in understanding phrases like "medial orbital gyrus".

Medial: towards the midline. Neuroanatomy always divides the brain into two hemispheres (the right and the left), with the midline being the deep groove between them. Anything closer to the midline is medial. It's a pretty relative term, many areas of the brain, no matter how far they are from the actual midline, are divided into medial and lateral, just to distinguish where in the area you are.

Lateral: away from the midline. Also a relative term.

And for more reference:

Superior: on top.

Inferior: on the bottom.

With that in mind, let's go ahead and start at the top:

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This is the area just under the top of my skull. You can see the top of my brain looks all wrinkled. The ridges are called gyri (gyrus for the singular), and the valleys are sulci (singular: a sulcus). So now you know what people are talking about when they say things like "gyrus frontus medius". Or at least you know one word out of the three, which is a start.

gyrus sulcus.jpg
(red arrow: gyrus, yellow arrow: sulcus)

You can also see here the interhemispheric fissue (otherwise known as the medial longistudinal fissure) running right down the midline like the cut in a hot dog bun. You know by now that your brain is divided into left and right hemispheres, and in fact you can really pull the brain apart for some way down the middle.

Functionally, your brain is divided into lobes. Four of these are easily distinguishable from the outside. Unfortunately, no outside pictures were taken of my brain, so you're going to have to deal with a drawing. And then a real picture, because the internets are gracious.

What you can see here is the brain divided neatly into lobes. If this were your brain, you'd be facing to the left side of the page. The first lobe, which tends to be the most interesting to the most people is the frontal lobe, shown here in red. It's divided from the back of the brain by the central sulcus, which is at about center, and from the bottom of the brain by the temporal sulcus. It is an area known mainly for its role in executive function. The back end of the frontal lobe is also the center of movement planning and execution.

Behind the frontal lobe and the central sulcus lies the parietal lobe, which in this drawing is blue. It starts right behind the central sulcus, and ends right in front of the occipital lobe, where we like to say there's some sort of invisible line that separates it out (the theoretical line is drawn from the perioccipital notch), but there isn't really. The parietal lobe is involved in taking in and integrating sensory information, like where you are in space, and what that thing is that just made that horrible squishing feeling under your toes.

the very back of the brain contains the occipital lobe, which you can see in green. As a testimony to just how important vision is to humans, that entire section of the brain is devoted to primary visual processing. That's JUST primary, secondary visual processing is somewhere else.

Below the frontal lobe and parietal lobe is the temporal lobe, shown in yellow. This has always been Sci's favorite lobe. I'm not really sure why. I think because it's so clearly defined, and the functions of it are beautifully localized. Functionally, the temporal lobe is divided into three parts, which are easily distinguished by the two sulci which separate the three main gyri. The top gyrus, the superior temporal gyrus, is involved in auditory processing, and is the first place signals go from signals in your ear. The bottom gyrus, the inferior temporal gyrus, is involved in higher level visual processing. And finally, the MEDIAL temporal lobes (closest to the inside of the brain, not the middle gyrus) are involved in memory (they are right near the hippocampus, one of the important brain areas for memory, and which you can actually SEE in one of my photos. We'll get to that in part two.

The last "lobe" of the brain that you can really see here is the cerebellum, which looks like a little brain hanging off the butt of your regular one. In fact, cerebellum MEANS "little brain". The cerebellum is both unbelievably complex and unbelievably simple at the same time. Sigh...the things I could say about the cerebellum. In this picture it's in orange, and the main functional things about it are that it integrates sensory processing and motor coordination, fine-tuning motor movements, and usuing information about position to keep you from running headlong into walls.
Here's a pic of a real brain which Sci has doctored to give you a better idea. In this photo, the eyes are facing right instead of left.

There is one more lobe of the brain, the limbic lobe. This one, however, is only visible INSIDE the brain, in a mid-sagittal section (remember hot dog slicing). A mid-sagittal section is one taken right down the middle of the medial longitudinal fissure.


So here you have it. In this picture, you can see at the lower right my cerebellum, cut neatly in half, as well as a nice shot of my brainstem with the pons particularly well displayed. But what I want you to really see here is this:


There. That rather sadly drawn red line (Sci can't draw at the best of times, and with a mouse it's even worse) outlines a sulcus that is sort of visible in the previous scan, and which deliniates what we call the limbic lobe. This here is some old brain. Old, that is, in comparison with things like the frontal lobe and all that higher processing kind of stuff. This part of the brain is concerned with olfaction, emotion, and the interior is concerned with really basic drives.

And with that, I leave you with part 1. I'm a little afraid that I will b0rk Scientopia if I put too many high-res shots in one post, anyway. Tune in next time for the interior of the brain, including some more pretty pics, and why Sci has a lovely basal ganglia.

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