The article delves into the concept of brain lateralization, explaining that it refers to the specialization of functions in specific brain regions rather than the entire brain performing all tasks equally. It refutes the outdated notion of complete hemispheric dominance, where one side (left or right) is entirely responsible for specific functions like creativity or logic. While acknowledging that certain functions, such as language processing, have been shown to predominantly reside in the left hemisphere, and facial recognition often in the right hemisphere, the article emphasizes that both hemispheres work together and that the brain's plasticity enables it to adapt and form new pathways if needed.
The discussion focuses specifically on language lateralization, highlighting the contributions of Paul Broca and Carl Wernicke. Broca's research, based on a patient's inability to speak after damage to the left hemisphere, led to the identification of Broca's area, crucial for speech production. Wernicke's subsequent work identified Wernicke's area, located in the upper temporal lobe of the left hemisphere, responsible for language comprehension.
The article concludes that while some functions are primarily located in specific brain regions, the brain's intricate connectivity and adaptability allow it to utilize various regions for complex cognitive functions. The simple notion of distinct hemispheric dominance is refuted, underscoring the brain's capacity for plasticity and inter-hemispheric collaboration.
Lateralization of function means that all functions in the brain are reserved to individual regions, rather than the entirety of the brain performing all tasks simultaneously. There are theories that each hemisphere controls different kinds of processes. For example, the theory of hemispheric dominance suggests that imaginative and creative tasks are reserved for the right hemisphere, and logical and mathematical tasks are reserved for the left hemisphere. This particular theory has been disproven because it overgeneralizes how the brain lateralizes functions between hemispheres. The brain uses both sides of the brain equally, rather than one more than another.
While certain things have been proven to be located in certain hemispheres, such as language processing being mostly located in the left hemisphere and facial recognition in regions of the right hemisphere, there is not enough evidence to say that one side of the brain is wholly devoted to one aspect of the human mind. In Sperry's experiments, patients whose corpus callosum had been severed could still process language when using their left eye (which links up to the right hemisphere). If language was wholly devoted to the left hemisphere, then they would not be able to read and understand a word at all unless looking at it with their right eye.
While many functions are lateralized to specific regions in the brain, this does not prevent the brain from using other regions to process other tasks. For example, patients that have undergone surgery to sever the corpus callosum can still perform tasks that are normally relegated to specific regions of the brain, because the brain is capable of creating new pathways for processes if necessary.
Language lateralization is the theory that language is processed by specific areas in the brain. There is evidence to show that some minor, specialized functions of language are located in the left hemisphere; however, it is unclear whether one hemisphere or the other is responsible for the bulk of language processing. It has been determined that the right hemisphere controls the left side of the body, and the left hemisphere controls the right side of the body.
French physician Paul Broca was an advocator for brain lateralization. He had a patient in 1861 whom he referred to as "Tan" because it was the only word that the patient could say. Following Tan's death, Broca performed an autopsy, which revealed that he had severe damage to the left hemisphere of his brain. Further studies showed that patients with similar conditions also had left hemisphere impairments, and thus Broca concluded that language is processed in a specific area in the left hemisphere of the brain, called Broca's area.
This diagram illustrates the location of different language processing centers, such as the ones named after Broca and Wernicke.
Several years later, German neurologist Carl Wernicke discovered something new about language processing. Some of his patients could speak but could not comprehend language. During his examinations, Wernicke discovered that these patients had lesions in an area of the brain that joins the upper temporal lobe of the left hemisphere. This area, now called Wernicke's area, has been determined to be where language is comprehended, while Broca's area is responsible for the motor functions of speaking language.
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