Aphasia (Language and the Brain)

One of the central features of our lives as living creatures is our ability to communicate- particularly, our ability to use language. When learning about how our brain processes, understands and utilizes language, we can study various brain functions and psychological processes. 

Evolutionarily, language is what makes us distinct from other species as our brains developed to be specialized for language function. The biological perspective of linguistics discusses language comprehension, production, and language as it relates to our evolution and traits as a species. 

Aphasia 

One way we study brain functions related to language is through the parts of the brain affected when one is diagnosed with aphasia. Some crucial parts of the brain necessary for language include the occipital lobe (the visual center at the back of the brain), the temporal lobe (the auditory center on the side of the brain), and the parietal lobe (which contains the motor center for speech muscles). These lobes allow us to see others speaking, hear what they are saying, and formulate a response. 

When individuals’ frontal regions of their left hemisphere are damaged, they may suffer from Broca’s Aphasia. Broca’s area is adjacent to the motor cortex and part of the frontal lobe, which is involved in processes such as thought, reasoning, judgment, and initiative. Broca’s Aphasia refers to a disorder of language production with individuals unable to express themselves in more than a single word at a time, omitting articles, conjugations, and grammatical inflections. For individuals with Broca’s aphasia, their interactive gestures, which are responsive in nature, are impaired. By connecting the location in which an individual is injured to the effects the injury has on their language, researchers can determine that the frontal lobe and Broca’s areas are involved in thought and language production. 

There are other forms of aphasia, including conduction aphasia and pure word deafness. Other forms of aphasia include conduction aphasia which is attributed to a disconnection between Broca’s and Wernicke’s areas causing difficulty in repeating what is heard. Pure word deafness makes it so that individuals are unable to comprehend language heard auditorily, only visually. 

Functional Magnetic Resonance Imaging 

Through fMRI scans, researchers can visually test and see the areas of the brain which contain increased activity to connect with a particular cognitive function. For instance, an fMRI scan confirms that the left inferior lobe- Broca’s area- has separate regions with different language functions. One of these functions is executive control, which is our ability to carry out, or executive, behaviors using cognitive abilities. Bilingual individuals utilize executive functions to control which language is being used and switch between them. 

Lateralization of Language 

An important factor of language in the brain is lateralization, which is where each hemisphere of the brain serves different purposes. Lateralization has been studied through split-brain research, where patients are presented with stimuli to one side of the brain. Such studies have shown the independent functions of the left and right sides of the brain. The brain functions contralaterally, where each half of the brain controls the opposite half of the body. The left hemisphere is dominant over the right for language, as Wernicke’s area and Broca’s area are within the left cerebral hemisphere. Interestingly, when the left hemisphere is removed at an early age, before the onset of speech, there are no major language deficits; this shows that the right hemisphere can compensate for the loss of the left. Such discoveries suggest that there is much more research to be done on lateralization and brain plasticity. 

Neuroplasticity

Neuroplasticity refers to the brain’s ability to change and adapt its structure and function throughout life. The brain’s elasticity and rapid neural formation allow babies and young children to learn language much easier than adults. Over time, neuroplasticity decreases as a person ages, making learning languages more difficult. Thus, the brain has evolved to learn, produce, and understand language. 

Sources 

https://www.e-cacd.org/journal/view.php?number=86

https://pubmed.ncbi.nlm.nih.gov/19747595/

https://repository.dinus.ac.id/docs/ajar/David_W._Carroll_Psychology_of_Language_.pdf

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4874870/

https://www.frontiersin.org/articles/10.3389/fpsyg.2017.01657/full

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