When looking at brain structure and function, the starting point for any learner is understanding the lobes of the brain. There are 4 main lobes – Frontal, Parietal, Temporal, and Occipital. Each lobe of the brain has a distinct function. The frontal lobe is known as the executive portion of our brain because it is in charge of planning, voluntary muscle movements, decision-making, personality, and speech. Given that the parietal lobe contains the sensory cortex, it is known as the sensory lobe and focuses on sensory perception and integration of all five senses. The occipital lobe’s role is visual processing as it contains visual areas (groups of neurons with the same function) which receive visual information from the opposite visual field. This means that the visual information from the right eye is sent to the left side of the occipital lobe for processing and vice versa. Similarly, the temporal lobe is involved in auditory processing as it includes auditory areas that each receive auditory information primarily from the opposite ear. You can easily remember this when you realize that the temporal lobes are on the lower sides of your head, near your ears.

In addition to the functions of the lobe of the brain, there are special “areas”, which are groups of neurons with the same specific function, in each lobe. These special areas are known as cortexes. The frontal lobe contains the motor cortex, which generates electrical signals that are relayed to motor neurons to direct body movement. The parietal lobe contains the somatosensory cortex (aka sensory cortex), and its function is to process incoming sensory information and integrate sensory and motor information for skilled movements to occur, like reflexes. The occipital lobe contains the visual cortex, which receives, separates, and integrates visual information. The temporal lobe contains the auditory cortex, which is involved in receiving and processing auditory information. Each cortex is responsible for responding to different stimuli and then initiating an action in response to that stimuli. A tip to remember which cortex is located in a specific lobe is that the major functions of each lobe are based on the function of the cortex it contains. For example, the frontal lobe is involved in voluntary movement, which is under the jurisdiction of the motor cortex.

The motor, visual, and auditory cortex functions are pretty straightforward and self-explanatory, given their names. The somatosensory cortex is a bit more complex, so let’s dive deeper into its functions. What’s interesting about the somatosensory cortex is that there is an unequal representation of the body parts it controls within the physical cortex area. The functions of the finger, hand, forearm, elbow, and entire arm, take up a large amount of space within the cortex. Similarly, facial features, such as the eyes, nose, and lips also use a significant amount of brain space. Our face and arms make up a large portion of our sensory cortex and neural connections since they are involved in more movement and dexterity. This makes sense given that our hands are what feel the world around us and help us perform both daily and complex tasks. Similarly, our eyes, nose, and lips are also involved in processing the world around us, whether it be through vision or through taste. For example, a beginner violinist can only play the correct note if they can see the string and their hand placement as well as feel the string’s tension and thickness. On the other hand, body parts like the intra-abdominal tracts, pharynx, and jaw take up smaller regions within the brain because they require less controllable movement or dexterity.

An interesting fact about the sensory areas and lobes of the brain is that, by accident, we have figured out many of their functions. The most famous example of this is Phineas Gage. In 1848, while 25-year-old Phineas Gage was paving the way for new railroad tracks to be laid, a situation occurred where the rod of the tamping iron he was using penetrated his left cheek upward and diagonally, puncturing his brain and blinding his left eye while exiting through his skull. Despite the gruesome injury, Gage miraculously survived and recovered quickly; however, he was no longer the same person. Before the injury, Gage was known as a capable, efficient, outgoing, and kind man with a well-balanced mind. However, post-injury, he became an extravagant, anti-social man who lied and used gross amounts of profanity, which was uncharacteristic of his previous self. Although Gage died around 12 years after his railroad incident, what’s significant about his case is that it showed researchers that the frontal lobe controls personality and decision-making. The damage the rod inflicted on Gage’s frontal lobe altered his personality as he began making different decisions than before.

Now that we understand the various functions of each area of the brain, we can transition to learning about brain plasticity. Brain plasticity is the ability of the brain to reorganize neural pathways based on new experiences. Whenever we experience something new, such as riding a bike for the first time, our brain incorporates that new information by building neural connections so that information can be maintained. Another way to think about this is that when we acquire new knowledge, our brain changes in response to that new knowledge. These functional changes are represented by the development of neural connections. It should be noted that the amount the brain changes is dependent on one’s age and previous brain injuries. The older you are and the more injuries your brain has suffered, the less plasticity your brain has. This diminishes the amount of knowledge you can truly remember, maintain, and recall from your brain.

So, why do we want our brain to be able to change? The answer lies within sensations and perceptions. As we experience new aspects of the world around us, our brain needs to incorporate this new knowledge to provide us with a more in-depth and informed understanding of our environment. Sensation is the process by which the central nervous system receives input from the environment via sensory neurons. Another name for this is bottom-up processing because we first get information from our environment and then transport it via electrical and chemical signals UP to our brain to process that sensory information. On the other hand, perception is the process by which the brain interprets and organizes sensory information, and then sends messages down to motor neurons to take action. Since information is first processed in the brain and is then sent DOWN through neural messages to motor neurons, perception is known as top-down processing.

Now, let’s transition into how we, as humans, actually process things. As you all probably know, we have 5 basic senses – vision, hearing, touch, taste, and smell. Vision, an electromagnetic sense, is the product of the conversion of light waves from the electromagnetic spectrum into electrical currents that are processed in the occipital lobe. Both hearing and touch are mechanical senses, as physical movement and sensation are converted into electrical currents. These currents are then processed in the temporal lobe and sensory cortex, respectively. The last two basic senses, taste and smell, are chemical senses. Taste is processed in the insular gustatory cortex while smell is processed in the olfactory bulb, orbitofrontal cortex, and vomeronasal organ.

However, there are other senses beyond the traditional five senses most people are familiar with. These four senses are the vestibular sense, proprioception, temperature, and nociception. The vestibular sense controls balance and motion and is located in the inner ear. Proprioception is the sense of the relative position of our body parts. For example, even if your eyes are closed and you have raised your hand upwards, you still know that your hand is above your head. Unlike the vestibular sense, proprioception is controlled in the parietal lobe. Our sense of temperature is a way for us to measure the relative heat of our environment. We have thermoreceptors located all over our skin that send temperature-related signals to the sensory cortex of our brain for processing. Finally, we have nociception, which is our sense of pain. Just like we have thermoreceptors for temperature-related sensations, we have nociceptors that send sensory information, in response to pain, to the sensory cortex for processing.

In this blog post, we covered the function of the 4 major lobes of the brain, the function of the brain cortexes, the inner-workings of brain plasticity, and the various senses we use on a daily basis. This article wraps up the basic anatomical and physiological aspects of biopsychology. The next series of 5 biopsychology blogs will discuss the application of biopsychology in a real-world setting, starting with the relationship between nature, nurture, and human diversity.