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

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 1800s 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 ‘Tan’ Slow, effortful, nonfluent speech with many omissions; but good comprehension on parle avec l’hemisphere gauche Carl Wernicke: patients with posterior lesions in the left hemisphere comprehension is impaired but speech is fluent

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

Wernicke-Lichtheim model Wernicke’s area Broca’s area Concepts (distributed) arcuate fasciculus Broca’s aphasia Wernicke’s aphasia 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