The cerebrum makes up a large portion of the brain. It is what people refer to when they describe someone as left- or right-brained.
The cerebrum is home to many smaller structures that regulate numerous core functions in the entirety of the human body. Functions controlled by minor structures of the cerebrum are the interpretation of sensory information, emotions, learning, problem-solving, motor control, and much more.
The outer layer of the cerebrum, the cerebral cortex, is referred to as “the hub of thought” and is integral to cognitive function.
Two hemispheres make up the whole of the cerebrum, the left, and right hemisphere. They control the symmetrical divisions of the body opposite to them: the left hemisphere controls the muscles on the right side of the body, and the right hemisphere controls the left muscles.
The two regions are connected by the corpus callosum and together compose what is considered to be a part of key characteristics setting humans apart from non-human animals.
The Left and Right Hemispheres
Although the left and right hemispheres do not function independently of one another, there are certain functions for which one hemisphere excels over the other. A brief overview of what the hemispheres are currently known to control is below:
|Left Hemisphere||Right Hemisphere|
|Analytical skills/Problem solving||Creativity|
|Language||Reflective, conscious thought|
|Calculations; Mathematics||Music interpretation|
|Muscles of the right side of the body||Muscles of the left side of the body|
Because the popular notion of being a left- or right-brained type of person isn’t exactly rooted in scientific evidence, the dominance of either hemisphere doesn’t make you more creative or give you more of a chance to pass a math test than your classmate.
What it does mean, however, is that whether you are left- or right-handed person is influenced by which hemisphere of your brain is dominant over the other.
The processes that drive this dominance are unclear and it’s not something that can be consciously controlled, outside of a practice session every now and then writing with the opposite hand.
Not only do the hemispheres control the muscles on the opposite side of the body, but the intake and processing of sensory information as well.
Aside from the left and right hemispheres, the cerebrum can be categorized into four distinct lobes: the frontal, parietal, temporal and occipital lobes.
The frontal lobe is where “executive functions,” such as the regulation and expression of emotions, language, reason, problem-solving, sexuality, and planning take place.
It is also where the primary motor cortex, the area of the brain responsible for controlling voluntary movement, is located. The Broca’s area, one of the two key areas in speech, is located in the frontal lobe as well.
The human frontal lobe is larger and more developed than any other organism – which is a partial explanation of why The Rise of the Planet of the Apes is never going to happen (at least in our lifetime) and, sadly, why the gorilla at the zoo won’t talk back to you.
The frontal lobe is the center of higher functions that separate humans from all other species, giving us the ability to communicate and form rational thoughts in a way that is not yet physiologically possible for other species.
The parietal lobe is situated directly behind the frontal lobe and separated by what is called the central sulcus.
This portion of the brain is responsible for taking in and interpreting tactile sensory information: touch, temperature, pressure, and pain. This area of the brain also controls the ability to taste – so next time you snap a photo of your meal for Insta, make sure to tag your parietal lobe and give it props.
The lateral fissure separates this lobe from the frontal lobe, as it is situated posterior to the frontal lobe. The temporal lobe is the control hub of a wide range of nervous system functions including the interpretation and distribution of sensory information and cognitive processes like the formation of memories and language recognition.
The primary auditory cortex is located within this lobe and receives sensory information related to hearing. The actual sensation of hearing and the processes by which we interpret auditory information (directional source of a sound, what type of sound, etc.) are controlled here. Recognition of language also takes place here.
Complex visual information, such as environments or images with many elements or a large variety of colors, is processed here in the temporal lobe as well.
This lobe is integral to processes that require memory: recall of information assigned to specific objects or environments, general retention of knowledge during learning exercises, etc. The formation of long-term memory specifically is a key function of the temporal lobe.
The hippocampus is a major structure that is also located in the temporal region.
[Fun fact, the term "hippocampus” is derived from the Greek word, hippokampus, which, when broken down means "horse” (hippos) and "sea monster” (kampos) because of this structure’s resemblance to a sea horse.]
The sea horse monster is also a part of the limbic system – a system primarily occupied with regulating emotions – and is integral to memory and learning.
The occipital lobe is central to visual processing. Interpretation of visual stimuli requires the ability to analyze information including depth, distance, location, light/color, and identity of the object being observed.
Information obtained by visual stimuli is also directly linked with memory. The involvement of the occipital lobe in the formation of memories is essential to recognition and memory recall.
This is another part of the cerebrum that is a functional component of the limbic system. The amygdala is located in the temporal lobes and is involved in many autonomic nervous system functions including physiological responses to fear (the “Fight or Flight” response) and the secretion of hormones.
There is one amygdala in each hemisphere (plural: amygdalae).
This structure is particularly concerned with regulating the emotions of fear, anger, and pleasure. As you can see, the processes and hormonal secretions that originate in the amygdala are all deeply reactive and instinctual in nature, however, it is involved in more sophisticated functions as well.
The amygdala is the structure that determines what memories are stored and where in the brain they are stored. This process is thought to be influenced by what emotions were evoked during a particular event.
A memory of your first kiss will be stored somewhere completely different than the one where you were horrified at the Six Flags Fright Fest (at least, I hope so).
This gray blob (gray matter, to be exact, located between the cerebral cortex and the midbrain) is more than just its looks.
Positioned under the cerebral cortex, the thalamus is involved in numerous sensory and motor functions and also partially controls the circadian rhythm by signalling the brain to reduce certain physiological functions during sleep.
The basal ganglia is a collective term that refers to a group of subcortical nuclei that are integral to motor control, learning, learning, and executive functions and behaviors such as those regulated by the frontal lobe.
The parts which collectively make up the basal ganglia are the putamen, caudate, globus pallidus, subthalamic nucleus, and substantia nigra. The caudate and putamen together are referred to as the striatum. Despite everything that they’re involved with, these structures are best known for their involvement in movement.
The olfactory bulb is a structure located on the inferior (bottom) portion of the cerebral hemispheres, on the anterior portion of the brain. There is one per hemisphere and they are attached to the cerebrum by an elongated structure known as the olfactory stalk or the olfactory peduncle.
As the name suggests, the olfactory bulb is essential to the sense of smell and is partially involved in taste as well.
Surface Area of the Cerebrum
A major factor in what makes humans so intelligent is the amount of surface area we have for neurons. The more neurons a brain (or entire nervous system) has, the more information that can be taken in, interpreted and retained.
The reason we have so much surface area is due to the folds, or “bumps and grooves” of the brain, known as gyri and sulci, respectively. Imagine that you have a very large carpet and on this carpet, you place a coin every square inch.
If you can fold this carpet enough, you can get it to be so compact that you can add more carpets with their coins and fit much more into that original space. This is what the gyri and sulci accomplish: fitting as many neurons as possible within the space of the human skull.
In this way, intelligence is not a measure of the size of the brain but correlated to the ratio of surface area to volume. Intelligence is also considered to be correlated to the proportion of the body which the brain constitutes, but that’s another story for another time.
The cerebellum is a massive portion of the brain and regulates countless processes that are essential to human survival and intelligence.
As a part of the central nervous system, this structure is certainly one that we couldn’t live without and is a key part of what keeps humans at the top of the food chain.