Source: Phineas Gage; Public Domain: http://commons.wikimedia.org/w/index.php?title=File:A_descriptive_catalogue_of_the_Warren_Anatomical_Museum.djvu&page=6
So remember on review of the brain structure, the brain is divided into two different hemispheres. We have our left brain and our right brain. And each hemisphere is further subdivided into four different parts, which we call lobes. There's the frontal lobe, the parietal lobe, the temporal lobe, and the occipital lobe. Each lobe, and different area, is related to a different type of behavior, or different mental processes. This is what we refer to as localization of function. Today, we're going to be reviewing the frontal lobe, and all the different mental processes that are related to it.
The frontal lobe is related to lots of different mental processes and functions that we recognize as being uniquely human. These are things like the control of our movement of our bodies, our long-term memories, planning, reasoning, and even judgment.
A lot of the ways that we learn about the frontal lobe are through damage to the frontal lobe, and the resulting changes in the personality and behavior of the people that have had their frontal lobes damaged. And there are two areas we'll look at specifically.
The first one is a famous psychological case of a man named Phineas Gage who, in 1848, had an accident in which he was using a tamping rod to tamp down, or to press down, on some explosives, which shot the rod-- which was a long thin rod with a spike on one end-- up through his brain. Specifically through the frontal lobe, the prefrontal cortex. He survived this accident, so don't worry about that. But his friends noted that there were specific changes within his behavior and his personality. He became a lot more quick-tempered and impatient. He was also very indulgent in things that were less acceptable. Different habits, like cursing, drinking, gambling, things like that. Before, he had also been very hardworking, but then afterwards, he couldn't plan for things, and he couldn't complete work. And there was also some intellectual damage, as well.
So you can see that the frontal lobe must be related to a lot of those areas, that it quickly changed in this person. And this led to a lot of the initial development about localization of function, and the different parts of the brain related to different behaviors and processes.
Another aspect of the frontal lobe, and damage to it, is through the use of the lobotomy. The frontal lobotomy was a surgical procedure that was especially popularized in the US during the 1940s. It involved disconnecting or removing certain sections of the prefrontal cortex of the frontal lobe. This was meant to deal with a lot of severe mental disorders, especially in difficult individuals. It was made popular in a famous book and film called, One Flew Over the Cuckoo's Nest. But the problem with it was that it led to really severe changes in a person's activities, and their personality. It made them very docile, but often made people vegetables, where they were basically unthinking sort of zombies walking around, or just laying comatose constantly. Eventually it was abandoned because of cruelty, and also the availability of new, more humane sorts of procedures.
But because of these sorts of things throughout history, we've determined that the prefrontal, and the frontal lobe specifically, are related to a lot of really important aspects. So let's explore some of those in more detail.
The first area to look at in the frontal lobe is the prefrontal cortex, which I've mentioned already. The prefrontal cortex is the front-most, foremost part the frontal lobe. So sort of this first half area of the frontal lobe, going all the way up to the front. This is involved especially with a person's sense of self. Things like their awareness of themselves, their impulse control-- stopping themselves from doing certain things-- and also their emotions. So when we look at things like Phineas Gage and the lobotomy, we're looking at damage specifically to the prefrontal cortex. Things that led to changes in their personality, or their activity, and things like that.
The prefrontal cortex is also related to reasoning and planning, so a lot of these higher level kind of cognitive abilities that we have as humans.
Another area of the frontal lobe to look at are the association areas, which are the rest of the frontal lobe, moving up towards the parietal lobe. Those areas help to process information, and in the formation of memory, especially a lot of the sensory information that's coming in, is processed in these association areas.
One of these association areas, that's important to language production specifically, is Broca's Area. Broca's Area is named for a French neurosurgeon named Paul Broca, who noticed that patients who had damage to this area of the brain were able to understand what was being told to them, but they couldn't actually produce the speech. This is a condition we call Broca's Aphasia, where they are unable to produce speech, even though they know what other people are saying to them. So specifically, this is dealing with trouble in the motor production of things, and problems with things like grammar and pronunciation. So any kind of language the person is able to produce is very difficult to understand.
The final area of the frontal lobe to look at is the primary motor cortex, which is this little area that's bordering the parietal lobe. And it's related specifically to movement, and the control of the body's muscles. Now this is arranged in a sort of homunculus, which is to say, it's arranged in a way that almost looks human, if you were to draw it out in this area.
It starts off with the feet at the top of the parietal lobe, and then moves through the body of the legs, and then the torso, all the way over to the arms, and then up to the hands themselves. After the hands, on to the face, and then the inside of the mouth and things like that. And then finally, sort of wrapping around into the internal organs and things like that.
The primary motor cortex is arranged in such a way that larger areas of the prefrontal cortex are devoted to more important and specific, or more sensitive, areas of the body. For example, the hands have a much larger area, because they're very sensitive and we need to manipulate them more closely. The face as well, and the tongue, because those are very sensitive and minute areas that we want to be able to control with a lot of detail.
So these are the three major areas of the frontal lobe to look at.