Language and Cognition Colombo June 2011 Day 5
Language and Cognition Colombo, June 2011 Day 5 Aphasia Dissociations
Defining aphasia Rao 1994
Defining language • • Speech? Communication? Thought? A separate system of knowledge? • Double dissociations
Double dissociations • Cognitive systems dissociate from one another • One can be impaired while another is (relatively) spared • This is taken as evidence that cognitive systems are distinct – the brain / mind is MODULAR in its organization • There are dissociations within language too
Localization of function • Phrenology – Gall, Spurzheim, early 1800 s • Different cognitive functions can be localized to different parts of the brain • Level of development of a particular function is reflected in skull formation • The sad tale of Phineas Gage • Dissociation of language from other cognitive faculties
Localization of language • Paul Broca (1861): patient • Carl Wernicke: patients with ‘Tan’ posterior lesions in the left hemisphere • Slow, effortful, nonfluent speech with many omissions; • comprehension is impaired but good comprehension but speech is fluent • on parle avec l’hemisphere gauche
Wernicke’s prediction • Predicted two language centers: – Broca’s area: speech articulation – Wernicke’s area: speech comprehension • Predicted a third ‘disconnection’ syndrome – damage to the arcuate fasciculus • “Conduction aphasia” Chris Rorden, University of Nottingham http: //www. psychology. nottingham. ac. uk/staff/cr 1/c 83 lnp 2. pdf
Wernicke-Lichtheim model Concepts (distributed) Wernicke’s aphasia Broca’s area arcuate fasciculus Wernicke’s area conduction aphasia Conduction aphasia: can produce and understand meaningful speech, but cannot repeat words they hear
Wernicke-Lichtheim model 1. Broca’s aphasia 2. Wernicke’s aphasia 3. Conduction aphasia 4. Transcortical motor aphasia 5. Dyspraxia 6. Transcortical sensory aphasia 7. Pure word deafness
Boston classification • Nonfluent aphasias – Broca’s aphasia – Transcortical motor aphasia – Global aphasia • Fluent aphasias – Wernicke’s aphasia – Conduction aphasia – Anomic aphasia • Alexia / Agraphia • Some rare syndromes: pure word deafness, optic aphasia • Boston Diagnostic Aphasia Exam (Goodglass, Kaplan & Barresi, 2001)
Classifying the aphasias • Advantages of classifying patients into syndromes – – – increases interscientist communication groups homogeneous patients for research and for therapy describes a set of behaviors for diagnostic purposes can help in determining a prognosis contribute data toward localization of lesion - advancing our understanding of the relations between brain and mind • Disadvantages of syndrome approaches – limits thought – exceptions may be more interesting and more fruitful for research – may force a label onto a patient who does not really fall into a particular syndrome category – presumes too much about premorbid functioning – localization issues may be vexed by individual differences
Cookie theft descriptions • Cookie jar …fall over…chair…water…empty • Well this is … mother is away here working her work out o' here to get her better, but when she's looking, the two boys looking in the other part. One their small tile into here time here. She's working another time because she's getting to. So two boys work together and one is sneakin' around here, making his work an' his further funnas his time he had.
Dissociations within aphasia
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