brain on chalk board

Different Functions of the Brain by Anatomy

drawing diagram of man touching fire and neurons to brainThe brain is the main central organ of the nervous system. “Nervous” referring to the nerves a.k.a. neurons. Basically, the nervous system is a communication network consisting of neurons that runs throughout the body.

Because of these neurons, we can tell if any part of our body touches something; the nerves on our skin sends signals to our brain when we touch something. And from that, our brain can tell that we actually “touched” something. That is the tactile sense, I suppose.

But what I am getting at is that the brain is the central hub that takes information from our senses, and processes this information.  And then with our brain, we can interact with the world.

So if the brain is responsible for understanding information of the world we interact with, through our senses, then isn’t it important to know how the brain works? What part of the brain does what? And what happens when that part of the brain is damaged, and therefore stops working? That is the aim of this article, at least to briefly touch what each part of the brain does.

So the brain is composed of many parts, but generalized into 5 regions, or 4 different lobes: the Frontal Lobe, Parietal Lobe, Temporal Lobe, Occipital Lobe and the Cerebellum.

The Cerebrum is the top part of the brain, consisting of all the lobes, ending at the cerebellum.

The Cerebral Cortex is the outer layer of neural tissue of the cerebrum; in other words, The Cerebral Cortex is basically the whole surface of all the lobes of the brain.

The Frontal Lobe

Location of Frontal Lobe

The Frontal Lobe is the front part of the brain. The frontal lobe is positioned in front of the parietal lobe, above and in front of the temporal lobe. From the forehead, the frontal lob extends all the way to the central sulcus on the top part of the brain.

Functions of the Frontal Lobe

The functions of the Frontal Lobe include:

  • Control of voluntary movement, like walking
  • Forethought, which is the ability to project future consequences resulting from current actions
  • Conscience, which is the ability to choose between good and bad actions, or better and best actions
  • Inhibition, which is the ability to override and suppress socially unacceptable actions
  • Salience Attribution, which is the ability to detect the state or quality that stands out relative to its neighbors, such as a red dot surrounded by white dots.
  • the ability to determine similarities and differences between things or events

Damage to the Frontal Lobe

So I already mentioned what some of the functions of the frontal lobe area up above. But how do scientists figure out these particular functions belong to the frontal lobe?

Well, in order to understand the function of the frontal lobe of the brain, scientists observe the behavioral change in a person or mammal with vs without a frontal lobe or undamaged vs damaged frontal lobe.

First, you should know that the frontal lobe contains the prefrontal cortex and the motor cortex. What do these parts of the brain do?

Well, the motor cortex is named intuitively. It controls our voluntary movement. Such that removing the motor cortex from  both hemispheres of the brain causes complete paralysis. However, the tactile sense of touch stays intact. You can compare the total removal of the motor cortex to those inflicted with ALS, like Stephen Hawking.

chalkboard diagram of prefrontal cortex region
The prefrontal cortex region of the brain is highlighted in red.

So what would happen if you remove only the prefrontal cortex, instead of the entire frontal lobe?

Well, a person without a prefrontal cortex would be unable to plan their actions, to inhibiting inappropriate behaviors & emotions, to verbally express oneself, and would have specific memory processing deficits.

First, it is observed that people with frontal lobe damage aren’t able to give appropriate emotional responses. For example, if a person is happy, he can’t express that happiness. It is also observed that frontal lobe damage may cause a person to show an excess or lack of emotions.

Depression may be observed. Also, a decrease of motivation may be observed for those with frontal lobe damage. That makes sense, since the frontal lobe contains most of the dopamine sensitive neurons in the cerebral cortex that are a part of the brain’s dopamine system associated with reward, attention, short-term memory tasks, planning and motivation.

To reiterate, a person’s reward, attention, short-term memory tasks, planning and motivation are harmed if the frontal lobe is harmed.

In fact, reduced dopamine activity (due to a gene called COMT of val variant prematurely breaking down dopamine, once dopamine is secreted into the synapse) in the prefrontal cortex (the prefrontal cortex is a part of the frontal lobe) is related to poorer performance and inefficient functioning of that brain region during working memory tasks, and increases the risk for schizophrenia.[1]

To summarize, the frontal lobe has many different roles. We need our frontal lobe for control over our voluntary movements (motor cortex), control over our emotions, our ability to plan and perform complex multi-step actions, to verbally express oneself with language, for certain memory processing (ie. focusing on one detail over another), and free will.

The Parietal Lobe

parietal lobe highlighted in yellow
The parietal lobe (highlighted in yellow) starts at the central sulcus, behind the frontal lobe, above the temporal lobe, and in front of the occipital lobe

The parietal lobe is a is positioned above the occipital lobe, behind the frontal lobe, and behind the central sulcus ridge. Indeed, the central sulcus outlines where frontal lobe ends and where the parietal lobe begins.

Function of the Parietal Lobe

The role of the parietal lobe is to integrate sensory information into specific abilities, including but not limited to:

  • Proprioception
  • Mechanoreception
  • Two Point Discrimination
  • Graphesthesia
  • Touch localization
  • Processing language

Proprioception is our ability to sense movement within our joints and joint positions. Proprioception allows us to know where our limbs are without requiring us to look at them. You say that proprioception allows us to “feel” where our body is in space.

Mechanoreception is our ability to feel tactile pressure or distortion- our sense of touch in other words.

Two Point Discrimination is our ability to tell apart that two nearby objects touching the skin are actually two distinct points, and not one.

Graphesthesia is our ability to recognize writing on the skin purely by the sense of touch.

Touch localization is our ability to perceive where on the skin you are touched lightly.

Homunculus map showing somatosensory cortex relationship to senses
By OpenStax College [CC BY 3.0], via Wikimedia Commons A cortical homunculus is a physical representation of the human body, located within the brain. A cortical homunculus is a neurological “map” of the anatomical divisions of the body. There are two types of cortical homunculi: sensory and motor.
The parietal lobe also plays a part in our brain’s ability to process language. Within the parietal lob region, there is an area called the “somatosensory cortex” which is right behind the central sulcus, located in the post central gyrus. The somatosensory cortex is responsible for tactile control over specific body parts- from the toes to the mouth.

The somatosensory cortex receives tactile sensory information from the nerves in the peripherals of our body that allows us to feel things and experience the sense of touch. These nerves send information to the spinal cord, then to the brainstem, through the thalamus, and finally to the somatosensory cortex within the parietal lobe of the brain.

With the tactile sensory information that the somatosensory cortex receives, it integrates sensory information (e.g. touch, pressure, temperature, and pain, spatial attention), producing a homunculus map, similar to that of the primary motor cortex.

So the somatosensory cortex ties back in with our language processing ability because we use our mouth and lips to form words and sound. And we require understanding the tactile sensations in our mouth and lips in order to properly form words and sounds, which is a part of human language.

The Temporal Lobe

Temporal Lobe Region Highlighted

The temporal lobe is under the frontal and parietal lobes. Specifically, the temporal lobe is located right beneath the lateral fissure (a.k.a. lateral sulcus) on both cerebral hemispheres of the mammalian brain. You can consider the lateral fissure to be the boundary between the temporal lobe and frontal-parietal lobes.

Function of the Temporal Lobe

There are quite a few functions that the temporal lobes fulfill in the brain, not just one. I’ll go ahead and list them down:

  • Storage of long-term memories
  • Processing of auditory information
  • Language Processing
  • Processing visual information

Long Term Memory Storage

The temporal lobes are required for the storage of long-term memories. Specifically, the area responsible for memory storage is the medial temporal lobes. In fact, the temporal lobe works with the hippocampus; the hippocampus is responsible for the formation of new memories, whereas the medial temporal lobe region stores those memories. The amygdala may also be involved in influences which memories formed by the hippocampus get turned into long-term memories stored into the medial temporal lobe region.

Auditory Information Processing

Another role of the temporal lobe is to process auditory information. Specifically, the temporal lobe processes auditory information from our ears; in other words, we are able to understand what we hear from our ears because of the temporal lobes. Without the temporal lobes, I’d imagine it would be as if you couldn’t hear. Or that you wouldn’t understand what you are hearing.

The areas of the temporal lobe involved with processing auditory input are the superior, posterior, and lateral parts of the temporal lobe.

Language Processing

So the temporal lobe also has a significant role in understanding language. Specifically, the temporal lobe holds the primary auditory cortex. The primary auditory cortex processes semantic meanings from auditory (speech) and visual information.

Furthermore, the temporal lobe also shares the Wernicke’s area region with the parietal lobe. The Wernicke’s area plays a role in comprehending or understanding auditory information (speech).

Wernicke’s Area

One region of the temporal lobe  that involves language processing is the Wernicke’s area.

Location of Wernicke’s Area

The Wernicke’s area is located in the posterior section of the superior temporal gyrus in the dominant cerebral hemisphere. In other words, the Wernicke’s area is located on one hemisphere of the brain (apparently not both) that is dominant, closer to the parietal lobe and the lateral sulcus, near the back of the temporal lobe, but of the temporal lobe’s upper region.

Function of the Wernicke’s Area

Anyways, I mentioned that the Wernicke’s area is involved in language processing. Specifically, the Wernicke’s area allows you to comprehend or understand spoken language.

Compare this to the language counterpart called the Broca’s area, which is responsible for speaking a language.

So when the function of the Wernicke’s area is disable, whether by stroke, brain lesion, trauma, etc.; then the person ends up not being able to understand spoken language anymore, as well as understanding the significant meanings sounds and noises can have.

For example, a person with a disabled Wernicke’s area may end up with fluent aphasia. Fluent aphasia is condition that although still allows a person to connect words with each other to form phrases and sentences, the meaning behind them are lost. In other words, the person with a damaged Wernicke’s area would end up speaking nonsense fluently.

Visual Information Processing

The temporal lobe also has a role in processing visual information. Specifically, the temporal lobe allows us to recognize, understand, and derive semantic meaning from objects that we see with our eyes, like a person’s face.

The Occipital Lobe

occipital lobe external internal anatomy
The internal and external view of the brain, with the occipital lobe highlighted in yellow. Shows the Occipital lobe in medial surface. It’s boundary is defined by two lines: the Parieto-occipital sulcus and the Basal parietotemporal line. Note that the Basal parietotemporal line is the artificial line which connects marginal end of the parieto-occipital sulcus with the preocipital notch.

The occipital lobe is the smallest of the four major lobes of the brain, located at the back of the brain that lies underneath the occipital bone of the skull.

Functions of the Occipital Lobe

The occipital lobe is the main center for processing visual information. Without the occipital lobe, we wouldn’t be able to see regardless of the state of the eyes. If the occipital lobe is significantly damaged (think lesions), then it can lead to cortical blindness- which is blindness specifically caused by a defect of the brain.

I’ll go ahead and list a few other visual functions that the occipital lobe provides, such as:

  • Visuospatial processing
  • Color differentiation
  • Motion perception

Visuospatial processing refers to the ability to perceive space as a 3D area in our mind. It allows us to gauge object distance, size, placement, as well as depth.

Color differentiation is simple enough. It is our ability to discern that red, blue, green, and other colors are different and that they exist. I would imagine that a person who couldn’t differentiate between colors would see the world in black and white, but this is just my speculation.

Finally, motion perception is our ability to tell that objects are passing by, that there a change in our visual information relates to the movement of an object.

Wikipedia defines motion perception as, “the process of inferring the speed and direction of objects that move in a visual scene given some visual input.”

To understand what motion perception is, a person who does not have the ability to perceive motion sees the world as a series of static images. Which sounds like a serious case of lag during a multiplayer video game session.

The Cerebellum

cerebellum front side view 3D models
By Images are generated by Life Science Databases(LSDB). [CC BY-SA 2.1 jp], via Wikimedia Commons
The cerebellum is located right underneath the occipital lobe, behind the brain stem. In other words, the cerebellum is roughly located under all of the other major parts or lobes of the brain, at the back of the head.

Functions of the Cerebellum

The function of the cerebellum is mainly to control motor movements, although the cerebrum may also play a part in attention, language, as well as regulating the fear and pleasure responses.

So the question is, what role does the cerebellum in our movements? The cerebellum isn’t responsible for initiating movement, but rather the cerebellum grants us the ability to coordinate our movements.

Motor coordination is our ability to combine and synchronize body movements. We need coordination when playing sports, dancing, walking, basically for almost all of the movements that we perform with our bodies. Without the ability to coordinate motor movements, we wouldn’t be able to sustain intended movements at all. This lack of coordination is called ataxia, and it looks something like this:

Ataxia usually happens when the cerebellum is damaged, further emphasizing  cerebellum’s role in coordination.

The Thalamus

position of thalamus in brain
By Life Science Databases. [CC BY-SA 2.1 jp], via Wikimedia Commons
The thalamus is divided into two walnut-sized parts. Both are found in deep in the center of the brain, between the midbrain and the cerebral cortex.

Function of the Thalamus

The function of the thalamus is to regulate the body’s voluntary motor control, consciousness and its sleep/wake cycle. It also regulates the senses of sight, sound, taste, touch and the sense of where the person’s body is in space. The thalamus decides which signals from the ears, eyes, mouth and skin to relay to its area in the cerebral cortex. The thalamus doesn’t relay information about the sense of smell.

The thalamus may also be involved in the regulation of some types of memory. The thalamus and the cerebral cortex operate in a feedback loop, especially when it comes to the sleep/wake cycle. The thalamus not only sends signals to the cortex, but the cortex in turn sends signals back to the thalamus.

Damage to the Thalamus

Damage to the thalamus can put a person into an irreversible coma.

Alternatively, deterioration of the thalamus by Fatal Familial Insomnia [wikipedia] leads to death.

A stroke that affects the thalamus can lead to a disorder where the patient feels pain or burning on one side of the body, accompanied by changes in mood.

The Hippocampus

3D model of hippocampus highlighted in brain
By Images are generated by Life Science Databases(LSDB). [CC BY-SA 2.1 jp], via Wikimedia Commons
The hippocampus is located in the middle of the temporal lobes of the brain, on both sides of the brain.

The Function of the Hippocampus

To simply put it, the function of the hippocampus is to form new memories. Without the hippocampus, you wouldn’t be able to form new memories, but you would be able to remember memories that are already formed. That’s because the hippocampus isn’t dedicated to the storage of long-term memories. But rather the temporal lobes are where memories are stored long-term.

A part of the hippocampus called the Dentate Gyrus gives a person the ability to form episodic and spatial memories.

Episodic memory refers to the memory of autobiographical events (times, places, associated emotions, and other contextual who, what, when, where, why knowledge) that can be explicitly stated or conjured. It is the collection of past personal experiences that occurred at a particular time and place.

Spatial memory refers to memories of spatial information such as the geographical layout of your hometown or the interior of a friend’s house. For example, Spatial memory is what allows British cab drivers in London to memorize the vast different travel routes into a mental map. You’ll notice that cab drivers like these have a better developed hippocampus as a result of using the hippocampus for the formation of spatial memory.[2]

The Corpus Callosum

3D brain anatomy of Corpus Callosum region
By Life Science Databases. [CC BY-SA 2.1 jp (http://creativecommons.org/licenses/by-sa/2.1/jp/deed.en)], via Wikimedia Commons
The corpus callosum, a.k.a. callosal commissure, is a wide flat bundle of neural fibers 10 cm long that connects the left and right cerebral hemispheres of the brain. The corpus callosum is responsible for allowing the two hemispheres of the brain to communicate with each other.

Function of the Corpus Callosum

The role or function of the corpus callosum is to allow communication between the two cerebral hemispheres of the brain. The corpus callosum allows for the integration of perceptual, cognitive, learned, and volitional information between the two halves of the brain. But the question is, what does the corpus callosum do for our cognition exactly?

Well, one way to tell is to cut the corpus callosum connection (Corpus callosotomy) between the two hemispheres of the brain. Corpus callostomy is usually done as an effort to limit the spread of epilepsy tween the two halves of the brain.

How do split-brain patients manage coordinated motor tasks?

Question:

I’ve read about how people, after a complete corpus callosotomy, can continue performing tasks requiring coordinated action from their right and left sides, e.g. running. Yet, if the brain hemispheres can not communicate directly, then in such cases, how does the coordination, or even the initiation of a gross action occur? Could it be like this:

Let’s say there is a stimulus to run, e.g. a dinosaur comes chasing and both hemisphere fire, yet whichever side gets going first, the other side starts complementing it with a response that will keep the body balanced and running. E.g. If one side speeds up, the other either agrees and speeds up accordingly, or maybe it quarrels. But both sides know that it is in their interest to escape the velociraptor.

Essentially, I’d guess that the hemispheres’ coordination is via the feedback that they receive from the already effectuated actions of their other half. Maybe this occurs on a subconscious level for both sides? Anyways, if true, I can’t understand how it doesn’t lead to massive problems, e.g. you see your Ex and one side want’s to interact and the other wants to walk off. On the other hand, does the operation enable legitimate multitasking?

Finally, as a extra, is there any resolution for the debate on whether split brains constitute to 2 incomplete minds in 1 body? It seems reasonable to say, no?

Answer:

They still can do basic motor tasks involving coordination, not complex (for a while, anyways). Basically, the corpus callosum connects both hemispheres of brain, this makes it easier for us to use our coordination more efficiently. So they still can do these functions, but it’s two different sets of motions and thought processes.

Use an example of tying your shoes. When you tie your shoe, you don’t think for both your hands, you just act and think of the action of tying your shoes, and act. They on the other hand, have to have two different thought processes for each of their movements, as they can’t connect the motions together properly.

These motor functions are simply more complex and complicated, rather than impossible

Sub Question:

But is anything known about the nature of the 2 independent thought processes that arise to perform, e.g. shoe binding. Suppose you are in a rush, then you may do the job faster, but for someone with a split brain, each side doesn’t know just how “fast” fast will be for the other, so it has to focus on continually adapting to the other. For us, feedback for our actions is of course vital as well, e.g. if my hand movement is off to knot the lace it is readjusted; but for the split brain, does each half perennially focus on “observing” the action of the other half in order to maintain overall coordination?

Sub Answer:

Much of the coordination and amplitude of movement is actually controlled in the cerebellum and basal ganglia, the pathways of which are not necessarily affected by lesions in the corpus callosum. Frontal lobe decides on a movement, cerebellum plans it and monitors feedback from the body, basal ganglia fine tunes it, and they project to both sides of the motor cortex which executes the action. So shoe tying and walking can remain synchronized through these other key regions.

[Source:Reddit]

Related Links

Books about the Brain

Sources

  1. Effect of COMT Val108/158 Met genotype on frontal lobe function and risk for schizophrenia. [NCBI] [Archive.org]
  2. London taxi drivers and bus drivers: a structural MRI and neuropsychological analysis [NCBI]

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