Aphasia and Language Disorders
Aphasia is an acquired impairment of language following brain damage, and its varied patterns have long informed models of how language is organized in the brain.
Definition
Acquired impairments of language comprehension or production due to brain damage, studied to understand the functional and neural architecture of language.
Scope
This topic covers the classical aphasia syndromes (such as Broca's and Wernicke's aphasia), the dissociations they reveal, and the use of cognitive neuropsychology to infer the components of the normal language system from selective deficits. It describes the disorders as evidence about cognition and the brain, and is not a guide to diagnosis or treatment.
Core questions
- What are the classical aphasia syndromes and how do they dissociate?
- What do selective deficits reveal about the components of the language system?
- How well do syndromes map onto specific brain regions?
Key concepts
- Broca's aphasia
- Wernicke's aphasia
- agrammatism
- anomia
- double dissociation
Key theories
- Classical aphasia typology
- The Wernicke-Lichtheim-Geschwind framework distinguishing nonfluent (Broca's) from fluent (Wernicke's) aphasia and relating them to lesion sites and a connecting pathway.
- Cognitive-neuropsychological dissociations
- The use of selective deficits, such as category-specific impairments for nouns versus verbs, to infer distinct components of the language system.
History
Building on Broca's and Wernicke's nineteenth-century observations, Geschwind revived the connectionist syndrome model in 1970, while cognitive neuropsychology from the 1980s used dissociations to fractionate the language system into components.
Debates
- Syndromes versus symptom-based analysis
- Whether aphasia is best understood through broad clinical syndromes or through individual symptom complexes mapped to specific processing components.
Key figures
- Norman Geschwind
- Harold Goodglass
- Alfonso Caramazza
Related topics
Seminal works
- geschwind1970
- goodglass1993
- caramazzahillis1991
Frequently asked questions
- How do Broca's and Wernicke's aphasia differ?
- Broca's aphasia involves effortful, nonfluent, agrammatic speech with relatively preserved comprehension, whereas Wernicke's aphasia involves fluent but often meaningless speech with impaired comprehension.