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Why is the prefrontal lobe the largest part of your brain? Learn about its amazing structure!
In the mammalian brain, the prefrontal lobe is the largest of the four major lobes and is located at the front of each cerebral hemisphere. The prefrontal lobe is separated from the parietal lobe by the central sulcus and divided longitudinally from the temporal lobe by a deeper sulcus. This unique anatomical structure makes the prefrontal lobe the most important area of the brain, responsible for a variety of functions that humans cannot ignore.
The smooth front part of the prefrontal lobe is called the anterior pole, which is one of the three poles of the brain and contains many important neural structures related to action and planning.
Structure
The prefrontal lobe occupies approximately one-third of the surface area of each hemisphere, and its structural division can provide us with a deeper understanding of neural functions. The lateral aspect of the prefrontal lobe is separated from the parietal lobe by the central sulcus and from the temporal lobe by the lateral sulcus. The prefrontal lobe can be further divided into the lateral, polar, orbital, and medial parts, each with its own specific gyri.
For example, the lateral part contains the superior frontal gyrus, the middle frontal gyrus, and the inferior frontal gyrus. The polar part contains the frontopolar cortex and the frontolimbic gyrus, and the orbital part contains several gyri.
The human prefrontal lobe does not fully mature until our 20s, which is closely related to the cognitive maturity achieved in adulthood. As we age, a small amount of shrinkage within the normal range is inevitable. The study noted that healthy participants between the ages of 60 and 91 were significantly different from those with Alzheimer's, showing less change in volume loss in the prefrontal cortex.
Function
The entire prefrontal cortex is considered an "action cortex" that focuses on a variety of actions, including skeletal movements, eye movements, speech control, and emotional expression. The largest part of the prefrontal cortex, the PFC, is primarily responsible for intrinsic purposeful mental action, including rational reasoning and planning for future consequences. The prefrontal cortex is also responsible for inhibiting socially inappropriate responses and helps us integrate long-term memories from different sources.
Clinical significance DamagePsychological tests are often used to assess prefrontal function, including the finger tapping test and the Wisconsin Card Sorting Test, which demonstrate the executive function of the prefrontal lobe.
Prefrontal lobe damage can occur in a variety of ways and can lead to a variety of different consequences. Common factors in the elderly include transient ischemic attacks (TIAs) and strokes, both of which can cause damage to the prefrontal lobe. Additionally, traumatic brain injury or neurodegenerative diseases such as Alzheimer's and Parkinson's are potential risk factors. Individuals with these disorders display different patterns of damage to the prefrontal cortex as a result of fetal alcohol exposure.
SymptomsAfter damage to the frontal lobe, the patient may exhibit inappropriate behavioral responses. For example, someone may understand the appropriate response to a particular situation, but their reality may not match that response. Common emotional expressions can be inconsistent and sometimes overly emotional. Loss of motivation and depressive symptoms are also quite common in these patients, making it difficult for them to complete normal daily activities.
Genes and DNA damage
A group of genes in the prefrontal cortex decreases in expression in people over 40, with this decrease being particularly pronounced in individuals over 70. These genes are crucial for functions such as learning and memory, synaptic plasticity, etc. Aging is accompanied by a significant increase in DNA damage, which is closely related to the decline in prefrontal lobe function.
History and Functional Theory
In the early 20th century, medical practitioners attempted to treat mental illness through psychosurgery such as lobotomies. Although this surgery can relieve symptoms in the short term, it may cause long-term damage to the patient's emotions and personality. However, current research has shown that the function of the prefrontal cortex is not a simple single process, but is composed of multiple interacting systems. This diversity of perspectives has prompted scientists to continue exploring more comprehensive theories to understand the unique functions of the prefrontal cortex.
Other primate studiesWhile early scientists believed that humans' prefrontal lobes were over-expanded relative to other primates, later neuroimaging studies challenged this view, finding that humans' prefrontal cortexes are not particularly proportional relative to those of other great apes. Currently, scientists pay more attention to the complexity of neural connections, which is one of the key factors that distinguish humans from other primates in cognitive ability.
How does the frontal lobe, with such a large and complex structure and function, affect our thinking and behavior?
