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Conduction aphasia, also called associative aphasia, is a relatively rare form of aphasia. An acquired language disorder, it is characterized by intact auditory comprehension, fluent (yet paraphasic) speech production, but poor speech repetition. They are fully capable of understanding what they are hearing, but show significant difficulty repeating phrases, particularly as the phrases increase in length and complexity and as they stumble over words they are attempting to pronounce.〔Conduction Aphasia. (n.d.). Retrieved from http://www.asha.org/Glossary/Conduction-Aphasia/〕 Patients will display frequent errors during spontaneous speech, such as substituting or transposing sounds. They will also be aware of their errors, and will show significant difficulty correcting them. Shallice and Warrington (1970) were able to differentiate two variants of this constellation: the reproduction and the repetition type. These authors suggested an exclusive deficit of auditory-verbal short-term memory in repetition conduction aphasia whereas the other variant was assumed to reflect disrupted phonological encoding mechanism, afflicting confrontation tasks such as repetition, reading and naming in a similar manner. Typical lesion location for conduction aphasia is on the supramarginal gyrus of the parietal lobe, posterior to the primary sensory cortex and just above Wernicke's area.〔Manasco, M. H. (2014). Introduction to Neurogenic Communication Disorders. Burlington: Jones & Bartlett Learning.〕 The classical explanation for conduction aphasia is that of a disconnection between the brain areas responsible for speech comprehension (Wernicke's area) and speech production (Broca's area), due specifically to damage to the arcuate fasciculus, a deep white matter tract. Recent research has challenged this notion on the basis that patients with conduction aphasia more often have lesions in the supramarginal gyrus or deep parietal matter. However, conduction aphasia remains a controversial topic from the understanding of its neurologic foundations. ==Presentation== Conduction aphasics will show relatively well-preserved auditory comprehension, which may even be completely functional. Spontaneous speech production will be fluent and generally grammatically and syntactically correct. Intonation and articulation will also be preserved. Speech will often contain paraphasic errors: phonemes and syllables will be dropped or transposed (e.g., "snowball" → "snowall", "television" → "vellitision", "ninety-five percent" → "ninety-twenty percent"). The hallmark deficit of this disorder, however, is in repetition. Patients will show a marked inability to repeat words or sentences when prompted by an examiner. After saying a sentence to a person with conduction aphasia, he or she will be able to paraphrase the sentence accurately but will not be able to repeat it.〔Manasco, M. (2014). Chapter 4: The Aphasias. In Introduction to neurogenic communication disorders . Burlington, MA: Jones & Barlett Learning.〕 When prompted to repeat words, patients will be unable to do so, and produce many paraphasic errors. For example, when prompted with "bagger", a patient may respond with, "gabber". Oral reading can also be poor. Patients recognize their paraphasias and errors and will try to correct them, with multiple attempts often necessary for success. Error sequences frequently fit a pattern of incorrect approximations featuring known morphemes that ''a'') share one or more similarly located phonemes but ''b'') differ in at least one aspect that makes the substituted morpheme(s) semantically distinct. This repetitive effort to approximate the appropriate word or phrase is known as ''conduite d’approche''.〔 For example, when prompted to repeat "Rosenkranz", a German-speaking patient may respond with, "rosenbrau... rosenbrauch... rosengrau... bro... grosenbrau... grossenlau, rosenkranz,... kranz... rosenkranz".〔 Conduction aphasia is a relatively mild language impairment, and most patients return to day-to-day life.〔 Symptoms of conduction aphasia, as with other aphasias, can be transient, lasting only several hours or a few days. As aphasias and other language disorders are frequently due to stroke, their symptoms can change and evolve over time, or simply disappear. This is due to healing in the brain after inflammation or hemorrhage, which leads to decreased local impairment. Furthermore, plastic changes in the brain may lead to the recruitment of new pathways to restore lost function. However, chronic conduction aphasia is possible, without transformation to other aphasias.〔 These patients show prolonged, profound deficits in repetition, frequent phonemic paraphasias, and ''conduite d'approche'' during spontaneous speech. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Conduction aphasia」の詳細全文を読む スポンサード リンク
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