Language and CognitionColombo, June 2011

Day 5Aphasia

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 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

http://www.psychology.nottingham.ac.uk/staff/cr1/c83lnp/c83lnp2.pdf

Wernicke-Lichtheim model

Wernicke’s areaBroca’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