aphasia
n. an acquired language impairment that results from brain damage typically in the left hemisphere. Common causes of damage include stroke, brain tumors, and cortical degenerative disorders (e.g., Alzheimer’s disease). Traditionally, a distinction has been made between expressive and receptive forms of aphasia, whereby individuals with the former primarily have difficulty producing spoken and written language and those with the latter primarily have difficulty comprehending spoken and written language. A more contemporary distinction, however, is commonly made between fluent aphasias, characterized by plentiful verbal output consisting of well-articulated, easily produced, but inappropriate or meaningless utterances of relatively normal length and prosody (rhythm and intonation), and nonfluent aphasias, characterized by sparse, effortful utterances of short phrase length and disrupted prosody. Fluent aphasias are associated with
posterior lesions that spare cortical regions critical for motor control of speech, whereas nonfluent aphasias are associated with anterior lesions that compromise motor and premotor cortical regions involved in speech production. Numerous types of aphasia exist, with eight classically identified: anomic aphasia, Broca’s aphasia, conduction aphasia, global aphasia, mixed transcortical aphasia, transcortical motor aphasia, transcortical sensory aphasia, and Wernicke’s aphasia. Also (but much less preferably) called dysphasia. —aphasic
adj.