Language disorders

1. Language disorders • We can learn a lot by looking at system failure • Which parts are connected to which • Examine the relation between listening/speaking disorders and physiology • Careful to not confuse individual difference with disorder! • Most useful clinical information comes from lesions

2. Researching cognitive neuropsychology • To show that 2 functions are found in separate areas of the brain, you need 2 cases • One where A is fine, B is impaired • One where B is fine, A is impaired • This shows that the two functions are independent • ‘double dissociation’

3. Separating of speech production & comprehension • We consider speech production & comprehension as spearate • What is the evidence? • There exists a double dissociation between the functions • Broca’s aphasia (production) • Wernicke’s aphasia (comprehension) • Each associated with a specific brain site

4. Broca’s aphasia • Symptoms: slow, difficult speech, little syntax, disjointed "Son ... University ... Smart ... Boy ... Good ... Good ... " • Associated with left posterior frontal lobe (motor cortex) • Side can change • Comprehension completely intact • Know what to say, can’t say it

5. Wernicke’s aphasia • Symptoms: word deafness, cannot understand syntax, word salad, poor comprehension 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 other part. One their small tile into her time here. • Associated with the left temporal lobe (connected to visual & auditory cortices) • Speech production normal • Rate, intonation, stress all OK

6. Relevant anatomy

7. Conduction aphasia • Symptoms: good comprehension, fluent speech, poor reading, poor repetition, word transpositions • Associated with left arcuate fasciculus • Connects Wernicke’s and Broca’s areas • Shows connections as important as processing sites

8. L. Arcuate Fasciculus

9. Imaging Broca’s aphasia case Conduction aphasia

10. Positron Emission Tomography (PET) scan

11. Modelling from neurological data • Deficits can give a lot of information • Writing production, speech, production, listening, reading, plus combinations! • Some deficits only apply to classes of words (eg. proper noun anomia) • Combine abstract cognitive models with clinical data to produce models • Cognitive neuropsychology! • Understand how brain injury can impair cognitive functioning

12. Ellis & Young (1996) – word processing • Three path information processing model • Three different ways of producing a word • One for normal speech; one for repetition; a third hypothetical one • Explains normal speech, speech pathology, repetition of unknown words

13. Ellis & Young (1996) Auditory signal AUDITORY ANALYSIS PATH 3 PATH 2 AUDITORY INPUT LEXICON PATH 1 SEMANTICSYSTEM SPEECH OUTPUT LEXICON PHONEME BUFFER Speech

14. Applications of the model • PALPA evaluations • Psycholinguistic assessments of language processing in aphasia • Various listening & repetition tasks to follow all 3 paths • Language tasks to check which node of the model is failing • Model can also be used to understand pure word meaning deafness • Cannot give a word’s meaning, but can repeat and write it down

15. Pure word meaning deafness • Patients can usually do lexical decision tasks OK • Word/fake word descrimination • Suggests the Auditory input lexicon is OK • Understanding of written material may be unimpaired – semantic system OK • Deficit thought to lie in connection between auditory input lexicon and semantic system

16. Auditory Phonological aphasia • Can be well explained by the E&Y model • Syndrome: can read and write, difficulty with place names and scientific terms • Jargon aphasia; proper noun anomia • Can easily repeat real words, but not non-words • Route via auditory input lexicon is OK • Route via auditory analysis system and auditory buffer impaired

17. Deep dysphasia • Extremely rare catastrophic speech disorder • Unable to repeat non-words • Frequent semantic errors on words (eg. ‘yellow’ for ‘blue’) • Abstract words more difficult to repeat that concrete ones • E&Y96 model explains this • Bad connection between semantic system and auditory input lexicon • Bad route between auditory analysis & phonemic buffer

18. Functional plasticity • Cortex areas become specialised • Not completely set • At an early age, functions can move from place to place (functional plasticity) • Language can be partly moved to right hemisphere, or distributed between them • Functional deficit at an early age can be overcome • Functions can be partly relocated (neural specificity) • Not complete functioning, but enough to cope

19. The Kennard Principle • Functional plasticity decreases with age (Kennard principle) • Not possible after mid-adolescence (14-16) • Certain functions lose plasticity first (Luria’s theory) • Not quite simple – sometimes insult at an early age is worse (leukemia patients) • Problem: hierarchy of systems • Neural systems are hierarchically arranged • If a required system is damaged, moving the function someplace else will not help