We’ve all heard someone describe themselves in one of these ways. “I’m more of a left brain person,” they might say. In traditional thinking, the left side of the brain is linear, analytical and clear cut. If someone works with math or empirical data on a daily basis—they may describe themselves as such.
“I’m a right brain person,” someone else asserts. Again following a line of traditional thinking, the right brain is popularly associated with creativity and the arts—this person may rely on an intuitive mindset, rather than an empirical one.
Both of these perspectives are disproven views into the significant complexity of the brain. Its lobes, its hemispheres, and the interconnected neuropathways where billions of neurons relay information are much more complex than the popular classification. The brain’s hemispheres work in conjunction—no cognitive activity is exclusive to the left side or right side. At a rudimentary level, a ready-made distinction between the functions of hemispheres comes down to a control over the opposite side of the body (left controlling right, and right controlling left). The reason for this swap in control comes from the function of the medulla, a portion of the lower brain stem where nerve control crosses to the opposite side of the body.
Every lobe of the brain exists in both hemispheres and, while each lobe has features and functions that are exclusive to it alone, many general traits are shared because of interconnected pathways. Lobes of the brain include the—frontal, temporal, parietal, and occipital; other sections of the brain are the brainstem and cerebellum.
What follows is an explanation of the various parts of the brain, the major functions controlled by each part, and how an injury to the area affects daily functioning.
executive function | definition: the group of complex mental processes and cognitive abilities (such as working memory, impulse inhibition, and reasoning) that control the skills (such as organizing tasks, remembering details, managing time, and solving problems) required for goal-directed behavior | (Merriam-Webster)
The frontal lobes are foremost in regulating voluntary movement, cognition and behavioral function. Executive functioning as regulated through the frontal lobes can be seen through problem solving and personal sequencing or planning. University College London psychologist Shelley Cannon noted in the article, “Frontal lobe dysfunction and everyday problem solving: Social and non-social function,” that the frontal lobes “…involve both non-social executive processes, social and emotional processes, and draw upon social and practical knowledge” (Cannon, 2004).
Cannon’s observation is significant because it affirms the wide swath of information the frontal lobes must process. “Non-social executive processes” are important in regulating and managing day-to-day activities—including ones that refer back to the Merriam-Webster definition (“working memory,” and “organizing tasks”). These also apply for what Cannon describes as “social and emotional processes” and drawing upon past experiences.
Related to this aspect of executive functioning is the degree to which a brain can control spontaneity, that when damaged may raise the potential for impulsivity, and a lessened line of control when problem solving. Included in the umbrella function of cognition and problem solving, memory and language are major facets of the frontal lobes. With the motor control aspect, decisions of whether or not to walk, run, sit down, or stand up (and so much more) rely on the agency of the frontal lobe. Frontal lobe damage would understandably lead to memory impairment or loss, and communication issues such as aphasia or apraxia could arise.
The frontal lobes function as a screen or filter. When information enters the brain and is processed through the frontal lobes, potential actions or responses to the environment or situation are filtered to determine the most appropriate action or response. If the frontal lobes are damaged, this filter may be compromised, and an individual may not be able to adequately filter responses—as is evident when someone with frontal lobe damage makes crude or vulgar remarks, or makes decisions without considering the consequences.
A famous example of frontal lobe damage that resulted in memory and behavioral changes occurred in the 1840s, when American railroad worker Phineas Gage was struck by a tamping iron. Entering through his left cheek and exiting through the top his skull, the tamping iron caused considerable damage to Gage’s frontal lobes. Those around him noticed that Gage often forgot short-term events and angered easily, a major change from the calm demeanor he previously displayed.
The second largest portion of the brain are comprised of the temporal lobes. The left temporal lobe is considered dominant for most people, and the right temporal lobe is considered non-dominant in most. Though this notion at a glance may seem like popular science akin to the “left brain” and “right brain” association, the reality is far from it. The left temporal lobe is “dominant” because its core function involving understanding language inputs, forming words and speech, and remembering these verbal inputs (information given through speech). Verbal communication is at the heart of human interaction and, as such earns its dominant moniker.
If someone suffers a left-hemisphere stroke, motor movement control on the right side of the body may be impaired. In addition, the person may have an inability to understand or express speech, thus underlining the significance of the left temporal lobe. Verbal communication is something that can be easy to take for granted. The right temporal lobe is categorized as non-dominant because of its association with non-verbal information. This includes facial expressions, gestures, and all body language.
As such, right temporal lobe damage may lead to an inability to understand non-verbal cues. Some visual-spatial hindrances may also come about. In an article by Dennis Chan of the Institute of Neurology in London and other collaborators, the authors explain that “the most common cognitive deficits…” following right temporal lobe damage are “impairment of episodic memory and getting lost” (Chan et. al., 2009). The episodic memory problems result from the role the temporal lobes play (along with limbic system structures) in solidifying memories for long-term retrieval, and getting lost results from the visual-spatial deficits typical of people with right temporal lobe damage.
The parietal lobes deal with proprioception, or the relationship of the body to the space it is in and moving around in it. The parietal lobes somewhat trump the temporal lobes in the input perception hierarchy, as its function is crucial for navigating through the environment. One of the most significant sensory inputs the parietal lobes receive is touch of any part of the body against any surface or object.
Gerstmann’s Syndrome results from damage to the left parietal lobe. The National Organization of Rare Diseases notes four areas of impairment among people with Gerstmann’s Syndrome:
- Dysgraphia or Agraphia—an inability to write.
- Acalculia—a loss of mathematical ability.
- Finger Agnosia—“difficulty identifying and distinguishing one’s own or another person’s fingers.”
- Left-Right Confusion—difficulty understanding left or right side of the body.
Damage to the right parietal lobe leads to Balint’s Syndrome characterized by ataxia (lack of balanced movement), apraxia (an inability to perform skilled movements, though the individual may be able to fully comprehend the movement), and simultagnosia (the inability of an individual to perceive more than one object at a time). People with right parietal lobe damage often lack the ability to navigate through the environment and have to rely on others for mobility. In turn, a lack of mobility may lead to an increased likelihood of falling,
As with other brain lobes, the occipital lobes work in conjunction with other parts of the brain. The primary function of the occipital lobes involves visual perception to supplement the visual-spatial work of the parietal lobe, help people to navigate within their field of vision, discriminate movements, and perceive color.
Damage to the occipital lobes hinders object perception, visual perception, and the recognition of written words. Given impaired visual perception, this occipital lobe damage may also affect a person’s ability to traverse the environment. Judging distances and object perception with the peripheral visual field is particularly hard. Some people report seeing flashing lights or stars in their peripheral vision.
The Brainstem and Cerebellum
The brainstem, split into three parts (the midbrain, pons, and medulla oblongata) is a crucial system at the back and lower portion of the brain that helps regulate a variety of functions including breathing, facial movements, balance, heart rhythms, and blood pressure. As such, the brainstem is absolutely vital for daily life. If the brainstem stops functioning, a person is unlikely to regain consciousness. Of the twelve cranial nerves responsible for engaging the five senses to respond to various stimuli, the brain stem contains ten. This renders the brainstem a part of the brain that is extremely important for everyday engagement with the environment.
The cerebellum—or “little brain”—is located in the back of and slightly below the occipital lobes. It is important for the performance of functional motor skills that are controlled by the lobes of the brain. In particular, though through the cerebellum’s responsibility is to coordinate movements that would otherwise be unrefined and awkward.
The inherent complexity of the brain does not mean it should be shrouded under a veil of pseudo-science, but rather engaged with in full. Given the brain’s vulnerability to injury—an examination of just how crucial a role every facet of it plays in our lives is very important. Even so, there are yet many more great resources and in-depth dives into the functions of each part of the brain.