The Cerebral Cortex
The cerebral cortex is the most important part of our brain (at least in the field of psychology) because it is what makes us human. The cerebral cortex (sometimes referred to as called "gray matter", is actually densely packed neurons. We actually are born with more neurons in our cerebral cortex than we have now, but they are young and inexperienced. As you get older the neurons learn to work together forming what we call neural networks. Let’s go back to when you were a kid and your parents taught you how to wipe your own butt. The first time you wiped it was awkward, you probably wiped poo poo everywhere and had to concentrate really hard. The neurons in your cerebral cortex were firing in the pattern of butt wiping for the first time. Every time you wiped your butt afterward, the neurons practice. Pretty soon those bunch of neurons that fire whenever you have to wipe your butt form a butt wiping team called a neural network. Today you probably do not even have to think when you wipe your tushy because your neural network has formed such a cohesive team- congratulations!!!
Now our cerebral cortex is pretty big and full of wrinkles- these wrinkles are call fissures. If you took out your cerebral cortex and ironed out all of the wrinkles it would be as big as a large pizza from Pizzeria Uno (but probably would not taste as good).
Now the cerebral cortex is divided into two hemispheres- the left and right hemispheres. For the most part the hemispheres exhibit what we call Contralateral control: which means the left hemisphere controls the right side of out body and the right hemisphere controls the left side. In general, right handed people (those with a stronger LEFT hemisphere) seem to be better at logical and sequential tasks. Left handed people (those with a stronger RIGHT hemisphere) are better at spatial and creative tasks.
Between the two hemispheres is a band of nerve fibers called the corpus callosum. The job of the corpus callosum is to help the two hemispheres communicate with each other. In some cases of people with severe epilepsy, the corpus callosum is surgically removed and the seizure activity decreases. However, these people lose the ability of there hemispheres to communicate to each other- they are called split brain patients. They actually have two separate brains inside their head, and one brain has no idea what the other is doing. For example, for most people the ability to see comes from the left hemisphere (which controls the right field of vision). So if a split brain patient sees an elephant in their left visual field they will not be able to say what they see, but they can write it with their right hand (but not left hand)- get it? Through the process of plasticity (which you should already know) most split brain patients will compensate and find ways for the hemispheres to communicate.
Areas of the Cerebral Cortex
We are going to talk about alot of places in the cerebral cortex-but there are also even more places that we will not talk about. Let’s call these places association areas– or areas that are involved in thought, memory, judgment humor, etc….- basically all areas not involved in sensory information or movement are association areas.
The Lobes of the Cerebral Cortex
Our cerebral cortex is divided up into four lobes (areas). However, to be more specific, we really have eight lobes because each lobe has a right and left side- remember the cerebral cortex is contralateralized!!!
The frontal lobes are located at the top part of our brain behind our eyes. The frontal lobe is where most of our personality hangs out. It is involved in the ability to control our emotions and abstract thought. There are two specific areas in the frontal lobe that you should know for the AP Exam:
Located in the back of the frontal lobe this thin strip of tissue sends signals (motor neurons) to tell our body to move. The things we move more (fingers) have more space devoted on the motor cortex, than parts of us we do not move much (pinky toes). The top of the motor cortex controls the bottom of our body and the bottom of the cortex controls the top of our body. If that is too confusing, just know that every time you voluntarily move your body, you are using the motor cortex in the frontal lobe.
Located in the left frontal lobe (at least for most people- in some left handed people, Broca’s area is on the right side), this areas controls the muscles in our mouth involved in speech. Speaking is a complicated task and we have a whole area devoted just to talking. If you damage Broca’s area (called Broca’s Aphasia) you will be unable to talk.
The parietal lobes are located in back of the frontal lobes on the top of our head. Most of the parietal lobes are made up of association areas. There is only one structure you should know:
Located in the front of the parietal lobe (directly behind the sensory cortex in the frontal lobe), this structure is responsible for us feeling touch sensations from our body. Every time you feel a type of touch sensations (both pleasurable and pain) the information is sent up by sensory neurons to the thalamus and sent to the sensory cortex so we can feel it. It is set up the same way the motor cortex is (see picture to right) in that the bottom of the cortex is responsible for the top of our body and the top of the cortex responsible for the bottom of our body.
Located in the very back of our brain, the occipital lobes are responsible for our eyesight. They contain the primary visual cortex which helps us interpret the information sent to us by our eyes (more specifically the retinas located in the back of our eyes- but we will get into that later on). Just to make your lives a little more confusing- do you remember that our cerebral cortex is contralateralized- well so are our eyes- kind of. You see, the right half of each of our retinas sends info to the left side of the occipital lobe and the left side of each retina sends info to our right occipital lobe. Follow that- yeah right!!! I will explain it in class.
Located just above our ears on both sides of our head, the temporal lobes control our hearing and contain the auditory cortex. What makes the temporal lobes so unique is that are NOT lateralized. The left temporal lobe is involved in BOTH the hearing from the right and left ear. There is one critical structure you should know that is in the temporal lobe:
Wernicke’s area is located in our left temporal lobe and is responsible for interpreting BOTH written and spoken speech. You use Wernicke’s area both the read and to listen. If you damage Wernicke’s Area (Wernicke’s Aphasia) you would be unable to understand what you are reading or hearing.