The cerebrum consists of many different sections that control various aspects within the human body. One thing you may notice when looking at the human brain is that it is shaped similarly to a walnut. That observation is actually quite accurate; the walnut is often split into two halves with a small area in the centre connecting the two lobes. Like a walnut, the cerebrum is split into two hemispheres (the left and right) and is joined via the corpus callosum. The two hemispheres perform different functions, and more often than not, people tend to use one hemisphere more vigorously than the other.
Lobes of the Cerebrum
Each of the hemispheres of the cerebrum contains four separate lobes, as seen on the picture below. They are referred to as the frontal lobe, the temporal lobe, the occipital lobe, and the parietal lobe.
The frontal lobe is the centre of reasoning i.e. your conscience centre and is positioned at the front of the cerebrum. If you touch your forehead, you are hitting the area where the frontal lobe is located. Directly behind it lies the parietal lobe and slightly below it lies the temporal lobe. This is also the area responsible for ensuring rational thinking and judgement: for an example, it would determine whether the risks you are taking are within safe limits or whether you are going too far. Say you were out on a Friday night partying: you would probably hear a nagging little voice in the back of your head telling you to be wary of how much you are drinking. However, the depressive effects of alcohol combined with other, more impulsive centres of your brain may overrule this voice and you may take things too far; I’m sure you’ve all done it at least once (I know I have), hence the next day you may receive a nasty hangover or worse as a result.
Additionally, there are two other major functions that the frontal lobe contains which have specific regions dedicated to them: Broca’s area and the motor cortex, the former of which is discussed in the page Broca’s and Wernicke’s Areas. As you may have already guessed, the motor cortex is the control centre of the brain for movement involving your skeletal muscles. Specifically, most of this work is done at the motor strip or primary motor area, which has areas of different sizes dedicated to controlling different parts of your body. The more complex and precise the movement that these muscles perform, the more space within the brain is needed. It’s similar to files on your computer; the more RAM it requires, the more space it’ll take. A Word document may contain only several KBs of data, compared to a movie file which may contain several GBs (for those of you who don’t speak computer, that’s over 1,000,000 times bigger, as one MB= approx. 1,000 KBs and one GB= approx. 1,000 MBs) The most chock-a-block spots in the primary motor area are dedicated to the muscles involved in creating speech, such as the lips, your larynx, the jaw muscles and your tongue.
There is also another area within the motor cortex, referred to as the pre-motor cortex, which is the command post for the orders needed to control your muscles. Every order to move your body is sent from there except for the orders related to speech-making; those are made from Broca’s area and bypassed directly to the primary motor area, as demonstrated by the graphic above.
Remember when someone dared you to try and tap your head and rub your tummy at the same time and then switch hands or rub your head and tap your tummy? You may recall if you were trying to complete this exercise, you were touching the top of your head. This is where the parietal lobe is located: it is behind the frontal lobe, above the temporal lobe and in front of the occipital lobe.
The parietal lobe performs two key roles: it is the numeracy and literacy centre of the brain and is also the area which processes information from the sensory nerves; it is the control centre for your sense of touch. These perceptions are coordinated between three different areas within the parietal lobe: the primary sensory area, the angular gyrus and the postcentral gyrus. Such information includes examining temperature (heat and cold), the feeling of vibration (such as an earthquake or something relatively harmless such a vibrating foot spa or even naughty items!) and detecting the degree of muscle movement.
You can probably guess the main functions of the temporal lobe based on where it is located within the cerebrum. I’ll give you a hint: it is located underneath the parietal lobe, behind the frontal lobe and ahead of the occiptal lobe. Here’s another hint: it involves two of the five senses.
OK, here’s one more hint, since I’m feeling generous: you’ve probably used these senses sometime today: one is all around you and you may or may not choose to ignore it (or even get annoyed at it), one you’ve encountered when cooking or cleaning up after your pets.
The temporal lobe is responsible for filtering your senses of hearing and smell.
Sound travels through the ear and eventually gets picked up via the primary auditory area where it is processed. There is a key difference between those who become deaf with time and who are born deaf: those who have become deaf with time have probably abused their eardrums by any number of reasons, such as work-related noise, rock concerts or constant noise exposure, whereas those who are born deaf generally have a disorder within their primary auditory area, despite their ears either being perfectly normal or deformed.
Another important area involved in the temporal lobe is Wernicke’s area.
The occipital lobe is located at the back of your head, and is located directly behind the parietal and temporal lobes. The information travels in this manner to the occipital lobe:
The occipital lobe’s job is translating what we pick up from our eyes into something we can see. Here’s a funny fact: the eyes actually pick up visual information upside-down, and it is our occipital lobe which is responsible for turning the image 180 degrees (to the proper way up). The occipital lobe is actually split into two sections: the primary and secondary visual areas. The primary visual area’s job is mentioned above, however the secondary visual area is the memory centre when it comes to vision: it helps in recall whenever we see something familiar as well as give meaning to the things that we see.