Ever heard of a split personality? How about a split brain? Well, we can’t be sure about the personality one, but brains can be split in two! In this lesson, you’ll learn that and much more on how the brain communicates within itself.

Left and Right Brain Communication

Communication between the brain hemispheres can be likened to an information highway.
Brain Hemispheres Communicate

Everyone seems to know that we get our signals to breathe, eat, walk, and laugh from our brain. But your brain isn’t just a machine that sends signals to the outside world, so to speak – it also communicates within itself. Your brain seems to have this secret little world of its own where it is actually talking to itself all of the time.

Now, it’s not that your brain is having fun whispering little jokes and secrets that no one else can hear. No, it’s super busy relaying information from the left hemisphere of your brain to the right hemisphere and vice versa in order to keep you alive. It’s like there is a big information highway between the two hemispheres of your brain that is always on, unless your brain is split in two, that is.

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I know what I just said sounds crazy since it normally doesn’t occur. People are typically born with one brain that’s intact and anything but split up. But as you’ll soon learn, there is a procedure where we, in a sense, slice the brain in half and keep the person alive at the same exact time! Oh, and we do it for a pretty good reason, too.

Let’s see how and why this occurs by first exploring the grey matter, white matter, longitudinal fissure, and corpus callosum of your brain.

The Cerebral Hemispheres

Let’s imagine we’re brain surgeons. It may be a bit scary and disgusting for you, but I’ll spare you the really gory details.

To get to the brain, we’d first shave the hair off of the patient. Next, we would slice through the skin on top of the skull. After removing certain parts of the bone, we would slice through a superficial layer covering the brain and would behold in front of our very eyes the brain itself. What we would see directly in front of us is known as the cerebral cortex. The cerebral cortex is slightly grey in color because it, unsurprisingly, has a lot of grey matter. The grey matter contains the bodies of nerve cells, and the nerve cell bodies are responsible for many things, including:

  • Keeping your nerve cells alive through energy and protein production
  • Storing information by way of a process we call memory
  • The processing and understanding of information from your senses, like your sense of vision and smell
The indentation that splits the two hemispheres of the brain is the longitudinal fissure.
Longitudinal Fissure

You’ll also notice that the cerebral hemispheres, the right and left hemispheres of your brain, have a really big indentation going right down the middle of the brain, splitting it into right and left halves. The large cleft that separates the brain’s left hemisphere from the brain’s right hemisphere is known as the longitudinal fissure.

The Corpus Callosum: Structure and Function

If we were to put our hands into the longitudinal fissure to try and separate the left and right hemispheres away from the center, we’d see that we can’t fully pry the cerebral hemispheres apart. There would be a very white-looking structure holding the two halves of the cerebral hemispheres together. This structure also helps your brain’s two hemispheres communicate with one another; it is called the corpus callosum. Again, the corpus callosum allows the right and left hemispheres of the cerebral hemispheres to communicate with one another.

If you’re wondering as to the reason why the corpus callosum is so white, it’s because it’s made out of white matter, and white matter is made up of parts of nerve cells that allow for the transmission of signals between two points. The white matter is essentially the highway by which electrical signals between a nerve cell body in one grey matter area travels to a nerve cell body in another grey matter area. Think of it this way: your grey matter is something like your internet modem or your computer, while the white matter is the cable connecting the two. Without the white matter, it would be far more difficult to signal and transmit information critical to things like memory formation and muscle movement.

Now it should all make sense. The corpus callosum connects each of your brain’s two hemispheres. The corpus callosum is also made out of white matter. Since white matter allows for communication and the corpus callosum is made out of this white matter, it should make sense that the corpus callosum, therefore, allows your brain’s hemispheres to communicate with one another.

With all of this in mind, you should now be able to make sense of how everything works together as a whole. For example, a little nerve cell body in your left hemisphere’s grey matter, the cerebral cortex, may want to involve a nerve cell body located in the grey matter of your right hemisphere’s cerebral cortex. How does the left nerve cell body communicate with the right nerve cell body in order to, say, form memory? It uses white matter! The nerve cell body in the left hemisphere will send a signal via white matter through the corpus callosum in order to get a message across to the nerve cell body located in the brain’s right hemisphere.

Diagram of the corpus callosotomy procedure
Corpus Callosotomy

When We Split the Brain in Half

In some unfortunate cases, a certain disease allows for lots of miscommunication between nerve cells and between the cerebral hemispheres to lead to seizures – a condition known as epilepsy. Sometimes, there’s almost no way in which to treat this disorder other than by way of surgery. In a surgical procedure known as a corpus callosotomy, the corpus callosum will be sliced in half in order to try and treat this condition. While we do not technically split our brain in half, this procedure cuts off the pathway of communication between the left and right hemispheres of our brain in order to minimize the negative effects of epilepsy.

Lesson Summary

With that in mind, let’s look into the important tid-bits of this lesson. Just like the fact that communication is important between people, so it is the case within the brain – the structure that actually lets you communicate in the first place.

Your cerebral cortex is made up of a collection of nerve cell bodies known as grey matter. In addition, your brain has a large groove called the longitudinal fissure, which separates your brain’s left and right hemispheres.

If you were to stick a pen into the middle of this longitudinal fissure as far down as it could go, you would hit a structure called the corpus callosum. The corpus callosum itself is made out of white matter, which is the stuff that allows your nerve cells to communicate information from point A to point B. This helps to explain why the corpus callosum helps the brain’s left hemisphere communicate with the brain’s right hemisphere.

Learning Outcomes

Upon completion of this lesson, you should be able to:

  • Describe cerebral cortex, grey matter, white matter, longitudinal fissure, and corpus callosum
  • Understand how the brain hemispheres communicate with each other
  • Explain how and why the corpus callosum is sometimes surgically severed