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Compare and contrast two different forms of aphasia. What part of the brain is specifically affected by each form and how would this affect the mental lexicon?
Language is stored and organized in the brain as a mental lexicons – units of memory that include semantic information about a word’s meaning, how it is spelled and sounds, as well as information about how it can be used in language, known as syntactic information (Gazzaniga et al., 2019). Damage to parts of the brain that store and access mental lexicons can have a devastating impact on a person’s ability to communicate – this loss of language is generally categorized as aphasia (Drago & Foster, 2011). This can include loss of the ability to produce speech, understand spoken or written words, as well as the inability to connect words to meaning (Drago & Foster, 2011).The most common cause of aphasia is vascular lesions caused by stroke but can also be caused by a traumatic brain injury, or neurodegenerative diseases like Alzheimer’s (Drago & Foster, 2011). Recovery and treatment for patients with aphasia is often limited; speech therapy can yield some improvement, as well as learning methods to compensate for loss of communication (Drago & Foster, 2011).
1. Broca’s Aphasia – This form of aphasia is a type of non-fluent or motor aphasia because it involves the loss of ability to produce words easily (Acharya & Wroten, 2021). The impacted areas of the brain include the left hemisphere of the inferior frontal gyrus of the frontal lobe, where Broca’s area is (Acharya & Wroten, 2021). For most people their dominant language area is in the left hemisphere; the exception is about 20% of left-handed individuals, whose dominant area is in the right hemisphere (The language areas, 2009). Broca’s area receives information about words connected with thoughts from Wernicke’s area via the arcuate fasciculus, and then processes the necessary commands to move the mouth to form words (The language areas, 2009).
When Broca’s area is damaged, patients can comprehend language, even written words, but have a difficult time with output, or signaling the production of speech (Acharya & Wroten, 2021). As a result, speech is often delayed, hesitant, and may be limited to two words, often without proper grammar (Acharya & Wroten, 2021). In addition to loss of ability to produce or repeat speech, some patients with localized damage to the inferior frontal lobe may also experience weakness or paralysis on the right side of their body (Acharya & Wroten, 2021). Treatment for Broca’s aphasia is very limited, and recovery peaks at about 2-6 months of therapy (National Institute on Deafness and Other Communication Disorders, 2017). As a result of this drastic loss of communication, many patients experience isolation and depression; they can understand everything that is going on around them but are unable to effectively express their own needs and thoughts (National Institute on Deafness and Other Communication Disorders, 2017).
2. Wernick’s Aphasia – This form of aphasia is a kind of fluent or receptive aphasia, because a patient has the ability to string together words and produce speech, but is deficient in their comprehension of language and their ability to connect words with meaning (Drago & Foster, 2011). The impacted areas of the brain include the posterior area of the left superior temporal gyrus – damage often includes the auditory association cortex, impacting interpretation of spoken language (Drago & Foster, 2011). Wernicke’s area sits in the upper temporal lobe, right next to the occipital and parietal cortices (The language areas, 2009). It is largely responsible for processing heard and seen words, by matching sound to meaning; the area surrounding Wernick’s area, known as Geschmwin’s territory, contains special neurons that help process sensory information of sound, sight, and body sensations to facilitate comprehension (The language areas, 2009). Wernicke’s area comprehends word and meaning association for both auditory and visual input, as well as finding the correct words to match thoughts generated internally for speech (The language areas, 2009). Once word association/comprehension is achieved, the information is passed through the arcuate fasciculus (a thick band of tissue) to Broca’s area for expression (The language areas, 2009).
Patients with damage to Wernicke’s area have a difficult time understanding spoken and written words, and cannot repeat phrases or name objects easily (Drago & Foster, 2011). It may be easier to comprehend visual material, like pictures, than words and speech; cognitive abilities outside of language are usually intact (Drago & Foster, 2011). Their speech is fluent, grammatically correct, and with normal cadence but may not make sense and is often nonsensical jargon (Drago & Foster, 2011). They may use words that make no sense or are non-existent in their speech, demonstrating a deficit in being able to cue up the proper word to match their intended meaning (Drago & Foster, 2011). Additionally, patients are typically not aware of their errors and may not realize that they are not making sense (Drago & Foster, 2011). As with most brain injuries, recovery is limited. However, non-invasive brain stimulation, neurotransmitter drug therapy, and speech therapy are all treatment options currently available – the first two mentioned are in trial phases, but nonetheless may give hope of further recovery for patients in the future (National Institute on Deafness and Other Communication Disorders, 2017).
Class, have you ever known anyone with aphasia? How would it impact your life if you had a brain injury that resulted in aphasia? I think that the most difficult part of aphasia would be the social impact of loss of communication, and maybe loss of employment.