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Broca's area and Wernicke's area
Receptive aphasia, also known as Wernicke’s aphasia, fluent aphasia, or sensory aphasia, is a type of aphasia traditionally associated with neurological damage to Wernicke’s area in the brain, (Brodmann area 22, in the posterior part of the superior temporal gyrus of the dominant hemisphere). However, the key deficits of receptive aphasia do not come from damage to Wernicke's area; instead, most of the core difficulties are proposed to come from damage to the medial temporal lobe and underlying white matter. Damage in this area not only destroys local language regions but also cuts off most of the occipital, temporal, and parietal regions from the core language region.
People with receptive aphasia are unable to understand language in its written or spoken form, and even though they can speak with normal grammar, syntax, rate, and intonation, they cannot express themselves meaningfully using language.
Receptive aphasia is not to be confused with Wernicke-Korsakoff syndrome.
When we want to speak, we formulate what we are going to say in Wernicke’s area, which then transmits our plan of speech to Broca’s area, where the plan of speech is carried out . Wernicke’s Area is located posterior to the lateral sulcus, typically in the left hemisphere, between the visual, auditory, and somesthetic areas of the cerebral cortex. A person with this aphasia speaks normally but uses random or invented words; leaves out key words; substitutes words or verb tenses, pronouns, or prepositions; and utters sentences that do not make sense. They have normal sentence length and intonation but without true meaning. They can also have a tendency to talk excessively. A person with this aphasia cannot understand the spoken words of others or read written words. Speech is preserved, but language content is incorrect. Substitutions of one word for another (paraphasias, e.g. “telephone” for “television”) are common. Comprehension and repetition are poor.
Patients who recover from Wernicke’s aphasia report that, while aphasic, they found the speech of others to be unintelligible. And, despite being cognizant of the fact that they were speaking, they could neither stop themselves nor understand their own words.
The ability to understand and repeat songs is usually unaffected, as these are processed by the opposite hemisphere. Melodic intonation therapy (MIT) has been pursued for some years with aphasic patients under the belief that it helps stimulate the ability to speak normally. There is some question as to the effectiveness of MIT. But more recent, and more rigorously conducted, research has revealed that MIT can be very effective at recovering language function.
Patients also generally have no trouble purposefully reciting anything they have memorized. The ability to utter profanity is also left unaffected, however the patient typically has no control over it, and may not even understand their own profanity.
Damage to the posterior portion of the left hemisphere’s superior and middle temporal lobe or gyrus and the temporoparietal cortex can produce a lesion to Wernicke’s area and may cause fluent aphasia, or Wernicke’s aphasia. If Wernicke’s area is damaged in the non-dominant hemisphere, the syndrome resulting will be sensory dysprosody — the inability to perceive the pitch, rhythm, and emotional tone of speech.
Patients who communicated using sign language before the onset of the aphasia experience analogous symptoms.
The symptoms of Wernicke’s Aphasia reveal how important language is because people with the aphasia cannot express their thoughts. Some patients with the disorder do find a way to overcome this road block, and use facial expression and motor gestures to communicate instead.
- 1) A deficit in the categorization of sounds. In order to hear and understand what is said, one must be able to recognize the different sounds of spoken language. For example, hearing the difference between bad and bed is easy for native English speakers. The Dutch language however, makes a much greater difference in pronunciation between these vowels, and therefore the Dutch have difficulties hearing the difference between them in English pronunciation. This problem is exactly what patients with Wernicke’s aphasia have in their own language: they can't isolate significant sound characteristics and classify them into known meaningful systems.
- 2) A defect in speech. A patient with Wernicke's aphasia can and may speak a great deal, but he or she confuses sound characteristics, producing “word salad” in extreme cases: intelligible words that appear to be strung together randomly.
- 3) An impairment in writing. A person who cannot discern sounds cannot be expected to write.
In popular culture
- In an episode of Boston Legal, Alan Shore is diagnosed with word salad which arises during periods of anxiety. Shore struggles with word salad for the rest of the show.
- The character of Samuel T. Anders suffers from a form of word salad in Season 4 of Battlestar Galactica after being hit in the head with a bullet during the mutiny aboard Galactica.
- In the television series The Twilight Zone, the episode "Wordplay" shows the point of view of a man gradually developing a form of receptive aphasia.
- The Monty Python sketch "Dr. E. Henry Thripshaw's Disease" involves a man (Michael Palin) whose discussion of the symptoms with his doctor (John Cleese) is in somewhat garbled sequence, a common symptom of the condition.
- Expressive aphasia
- Conduction aphasia
- Transcortical sensory aphasia
- Kolb & Whishaw: Fundamentals of Human Neuropsychology (2003) page 505
- Kolb & Whishaw: Fundamentals of Human Neuropsychology (2003) page 506
- Hébert S, Racette A, Gagnon L, Peretz I (August 2003). "Revisiting the dissociation between singing and speaking in expressive aphasia". Brain 126 (Pt 8): 1838–50. doi:10.1093/brain/awg186. PMID 12821526.
- Schlaug G, Marchina S, Norton A (July 2009). "Evidence for plasticity in white-matter tracts of patients with chronic Broca's aphasia undergoing intense intonation-based speech therapy". Ann. N. Y. Acad. Sci. 1169: 385–94. doi:10.1111/j.1749-6632.2009.04587.x. PMC 2777670. PMID 19673813.
- Kolb & Whishaw: Fundamentals of Human Neuropsychology (2003), pages 503-504. The whole paragraph on Luria's theory is written with help of this reference.
Klein, Stephen B., and Thorne. Biological Psychology. New York: Worth, 2007. Print. Saladin, Kenneth S. Anatomy & Physiology: the Unity of Form and Function. New York: McGraw-Hill Higher Education, 2010. Print.
- Aphasia Center of California in Oakland, CA, U.S.