So here we go, the Neuroanatomy Checklist.

You’re reading the book. It is all about the book! To begin with, our biggest concern is memorizing all those structures found on your check list. If we just look at the brain and its surfaces, we see a deep groove down the middle separating the two cerebral hemispheres: the longitudinal fissure.

You now know the cerebrum (everywhere there are gyri and sulci) is divided into lobes and their names are easy. If you pull the temporal lobe away from the parietal lobe above it, you open up the lateral fissure and see mor gyri and sulci down at the bottom of this opened lateral fissure and that is the hidden Insula or Insular lobe. Never confuse the cerebrum from the cerebellum which has those tiny ridges on it and it looks like someone glued a cauliflower onto the backside of the brain. The groove between the occipital lobe above and the entire cerebellum below is the transverse fissure.

ONLY LOOK AT THE Precentral Gyrus and Postcentral Gyrus in the above picture.

Notice that between the frontal lobe and the parietal lobe there is a sulcus separating them. This is the Central Sulcus. It is the dividing line between the frontal lobe and the parietal lobe. The gyrus in front of the central sulcus is obviously the precentral gyrus and the gyrus behind the central sulcus is the postcentral gyrus.

Here the lateral fissure is labeled as the lateral sulcus (either name is acceptable).

So, you may be asking, “is there a sulcus between the parietal lobe and the occipital lobe?” NOPE. Not all of our brains are folded the same way. They are mostly the same with the position of the gyri and sulci but not exactly. So not all of our human brains have a sulcus right at the boundary between the parietal lobe and the occipital lobe. So that line is mapped out by neuroanatomists and called the parieto-occipital sulcus (even though there may not be a sulcus there at all). May of the companies that make brain models will put a sulcus into the model but that may not be the case in your brain. Many, but not all human brains may have a sulcus right where we’d like it to be as the parieto-occipital sulcus seen on an inside view of a cut down the middle brain as seen below.

The models we have at school place a sulcus there and call it the parieto-occipital sulcus. But again, this sulcus is actually mapped out on a human brain by the neuroanatomists. This ‘cut’ of the brain would be considered a midsagittal section of the brain made by using a long knife and starting by placing the knife into the longitudinal fissure and cutting the tissue all the way through.

This midsagittal section will reveal a lot of internal structures on our checklist.

The precentral gyrus is also called the ‘primary somatic motor area’ because it is within this gyrus that all your ‘thoughts’ about doing a voluntary motion begin. So, the nerves from the precentral gyrus go to all your voluntary muscle cells. Since these motor pathways are important to movement, they have been mapped out and called the pyramidal tracts. Why ‘pyramidal’? Because if you look at the neurons that are found in the precentral gyrus with a microscope, they are bigger than all the other neurons in the brain and they are pyramid shaped. The term ‘extrapyramidal’ refers to all the other neurons in the entire brain. That is a lot of brain cells.

Can I ask you to identify them? No. But you now know the terminology.

First of all you can recognize this as a coronal section (see the diagram in the lower left of this picture above). A collection of nerve cell bodies will make that area look gray (gray matter). There are several areas of gray matter that have names. One is the caudate nucleus located just lateral to the lateral ventricles (get it, you can find the caudate

nucleus ‘lateral to the lateral ventricle’). Now look at the very center of the coronal section of the brain, it is labeled here as the hypothalamus. Let’s move out, away from the dead center of this view of the brain. Next to what they label as the

hypothalamus is a band of white matter that extends upward. That is the internal capsule. Notice that the internal capsule (this band of white matter) runs right past the caudate nucleus. Next is the globus pallidus, it is inside the putamen and triangular in shape, the ‘inner, triangular globus pallidus’. Just outside of the globus pallidus is the

putamen, the ‘outer, arching putamen’. If you keep on going outward is the very, very thin line of gray matter the claustrum. Not many diagrams or pictures of the brain even show or label the claustrum. And if you go out further you reach gyri and sulci, the hidden lobe of the insula. From there you are in the lateral fissure. The basal ganglia or corpus striatum = caudate nucleus + putamen + globus pallidus. Since the putamen and globus pallidus are so close sometimes they appear as one big gray matter island which is called the lentiform nucleus. Lentiform nucleus = putamen + globus

pallidus.

The corpora quadrigemina are the 4 raised, white matter lumps seen on the backside of the midbrain. The 2 upper white matter raised lumps are the two superior colliculi and the 2 lower white matter raised lumps are the inferior colliculi.

Corpora quadrigemina = 2 superior colliculi + 2 inferior colliculi. This area or region of the brain can be called the tectum.

Now the hypothalamus and the hypothalamic structures. The thalamus surrounds the third ventricle. So the very bottom of this area is the hypothalamus which you can see if you look at the underside of the brain. Below is not the best

picture but it does show the hypothalamus and the structures you can find there. From front to back these hypothalamic structures are the: optic chiasm (where the two optic nerves cross – a famous landmark, ‘the big white X’); infundibulum

(a thin stalk that attaches the pea-sized pituitary gland to the hypothalamus) (in most all pictures of the brain the

pituitary has been torn off and all one sees is a broken infundibulum); tuber cinereum (just open space of tissue, nothing special to see); mammillary bodies (very easy to spot, two, round, raised masses).

In the photos above, OC is the optic chiasm. Inf is the infundibulum with the pituitary gland removed. MB are the mammillary bodies. Also notice these two photos of the underside of the brain have the cerebellum highlighted in

orange.

That is a good start. I will leave it up to you to find pictures (many supplied by me that you can find on our website) of the remaining structures listed on our checklist. But let me mention a couple more things about tricky to identify structures. One of those is the intermediate mass. It is a band of tissue about as thick as a pencil that runs right through the 3rd ventricle, from the wall of the right thalamus to the wall of the left thalamus. So, if the intermediate mass runs from the right side of the 3rd ventricle to the left side of the 3rd ventricle, it is a thin, bridge of tissue surrounded by CSF in

the 3rd ventricle. Now image you cut the brain in half with a midsagittal section. You would see the intermediate mass cut in half also. It appears as a little nub of tissue sticking up from the wall of the thalamus and that is why.

The red nucleus and substantial nigra are internal structures only seen if you cut the brain right through the midbrain section. Remember that the midbrain is just about ¾ of an inch of tissue just above the pons and cerebellum and just below the hypothalamus.

We are not responsible for learning about Parkinson’s disease but the best pictures of the substantia nigra (that is diminished in people with Parkinson’s disease) are those about Parkinson’s disease. The above diagram shows where you would cut the brain to find it and where it is in the midbrain. Below you see the position of the red nucleus.

The cerebellar structures are straightforward. What are those cerebellar peduncles anyway?

The brainstem is defined as the: midbrain + pons + medulla oblongata.

Notice that the cerebellum is connected to these three parts of the brainstem by nerves that run back and forth between the cerebellum and the midbrain; between the cerebellum and the pons; between the cerebellum and the medulla oblongata. As you can see, the cerebellum is pressed tightly up against all three brainstem structures. The nerve bundles (tracts) that run from the cerebellum into the three parts of the brainstem hold the cerebellum tightly up against the brainstem. So, you really cannot see these connections, these cerebellar peduncles. The only way to see them is to remove the cerebellum to get it out of the way. But in order to remove the cerebellum you have to cut through these three peduncles since it is these peduncles that are holding the cerebellum onto the brainstem. See the predicament? So, the only images there are of these three peduncles is a view of the brain no one on earth will recognize. It is a rear view of the brain with the cerebellum removed and the flat, cut surfaces of these three peduncles.

The diagram above shows the superior cerebellar peduncle; the middle cerebellar peduncle and the inferior cerebellar peduncle which in this view you do not really see.

Spend time with your checklist and learn how and where to identify each structure on the brain using the photographs and diagrams provided on the website.