Disorders of Lexical Selection Garret 1992b

1. Disorders of Lexical SelectionGarret 1992b Brian Nisonger

2. 4 types of Linguistic errors • Message to Lemma Representation • Lemma to Word Form Representation • Word Forms to phonetic representation for connected speech • Speech representation to motor representation • This paper deals with the first two

3. Lexical Disorders • Aphasias • Loss of usage or comprehension of words • Broca’s Aphasia • Characterized by the inability to produce complete grammatical sentences • May be missing function words, pronouns or other categories • Comprehension may or may not be impaired • Wernicke’s Aphasia • Can produce “fluent” sentences • Usually semantically nonsensical • Comprehension is impaired

4. Lexical Disorders-II • Dyslexias • A reading based learning disability that impairs the ability to read • Deep Dyslexia • A reading disorder where semantic errors occur • Bush=>Tree • Antique=>Vase • Uncle=>Nephew • Alzheimer's disease • More on this later

5. Semantic Deficits of Lexical Selection • Normal Errors vs Lexical Disorders • Similarities • Word Substitution Errors • Synonymic • Antonymic • Associative • TOT states • Differences • Grammatical Categories • Hypernyms

6. Hypernym Problems • Object Oriented Programming • Inheritance • Animal=>Horse • Plant=>Flower • Supertype • Generally if W1 entails W2 then W2 is a hypernym of W1 • Substitution rare in normal speech errors, common in lexical disorders

7. Categorical Organization • Alzheimer’s Patients • Visual Naming Task • Hypernym substitution • General substituted for Specific • Errors may be related to normal speech when a word is unavaliable • I bought a plant • I bought a flower

8. So what does it mean so far? • Lexical Representations in the brain • Message=>Lemma • Lemma=>Word Form • Word Form=>Phonetic/Orthographic representation • Specifically divided Phonetic from Orthographic • Deep Dyslexia only orthographic • Other aphasias can be both phonetic and orthographic • More on this later • Concepts Space • Hierarchical in nature • Semantic Fields • More on this later • Garret 1992a

9. Lexical Retrieval System • Parallel Featural Tests • Linked Decision Tables • Table internal test parallel • Table -> Table serial • Might account for loss within categories • But ability to categorize within fields

10. Semantic Field Effects • Selective Impairments • Loss of ability to generate words from specific domains • Major • Concrete/Abstract • Living/non-living • Animate/Non Animate • Interesting cross phenomena with Worlds Languages? • Minor • Color Items • Food Items • Numbers • Baseball Players • Still possible to recognize words are of a certain category for some aphasia and other disorders but not produce them

11. More Field Effects • Affected categories • As low as 10% generation • Non-affected categories • Near normal performance • Field Effects stable across time • Rare or common words had no affect on Field effects • For example • Animal->Bear • Fruit->Prickly Pear

12. How does it fit in with the model? • Semantic Fields are a set of Lemmas • Grouped by specified functional similarity of concepts • Possibly used for rapid evaluation of alternatives in production • Lexical Ambiguities • In normal errors we see this affect as well • Garret 1992a • Aphasic Loss • Major vs Minor categories

13. Some Distinctions and Cross Classification • Examples • Possible to have losses in Concrete Inanimate category • No loss in Concrete Animate category • Living vs NonLiving • Seems to have less cross classifications • Sensory description • May not be relevant for inanimate non-concrete • Functional • Not relevant for living things but very relevant for inanimate • May be explained by other factors, but interesting

14. Higher Level Feature Errors • Wheel->Foot • Analogical relation between target and intrusion • Function • Mode of motion • Limbs • Foot • Mode of motion • Drive Train system • Wheel

15. Where are we at • Clear field effects in aphasic errors • Similar to effects noted in normal speech • Evidence for difference between • concept representation=>lemma representation • concept representation=>perceptional represention

16. Causes of Semantic Error • Need to categorize errors • Components of lexical system • Production • Comprehension • Most accounts don’t separate • Concept • Lemma • Two major categories of errors • Conceptual impairment • Lemma processing • Concept=>Lemma • Lemma Replacement Failure • Lemma=>Word Form • Word Form Output System Error (Possible 4th category)

17. Possible Reasons for Multiple Semantic Activation • Semantic Spreading • Multiple words are activated • Message=>Lemma • Message fragments can activate multiple lemmas which then are filtered through by more completed message fragments

18. Failure of the Output System • Generation • Failure to filter alternative lexical candidates • Failure to produce lexical candidates • Possible correlation to normal speech errors • No real evidence besides intuition

19. Auditory vs Orthographic • Loss of category can be specific to either auditory or orthographic forms • Loss of abstract for example may be present in auditory experiments but absent in orthographic experiments

20. Modality-Specific Failures • Modality • Verbal • Non-verbal systems • Semantics may be independent of the verbal system

21. Semantic Modality • Tactile naming experiments • Ability to mime usage of object • Inability to name the object • No knowledge of name • Not TOT • May cross classify with semantic field effects • Loss of specific categories in non-verbal naming tasks such as tactile naming

22. What is semantics? • Possible that semantics may not be just limited to “ lexical meaning” • Usage • Visual recognition • Relative Size • Relative Location • Visual problem solving intersections

23. Syntactic Category Effects • Open Class • Nouns, verbs, adjective, adverbs • Closed Class • Determiners, Prepositions, modals, negation, predicate markers

24. Closed Class Retrieval Failures • Comprehension • May or may not have inability to comprehend grammatical function words • Production • “Telegraphic” • “Doctor office Monday teeth” • No link between inability to produce grammatical words and comprehension of grammatical words

25. Types of closed class failures • Agrammatical • Inability to produce grammatical categories • Paragrammatical • Producing the wrong grammatical categories • Usually comprehension problems • Overlap • In Hebrew grammatical category cannot be omitted • Broca’s aphasia patients often pick incorrect endings • Broca’s aphasia = Agrammatical

26. Closed Classes Failures of Deep Dyslexia • Fewest errors with concrete nouns • Highest errors for closed classes • Inability to read closed class words in isolation • Longer passages may provide context for guessing • Possible failure of lemma=>word processing

27. Alternate Retrieval System for Closed Classes • Failures in open class not found in closed class • Phonemic paraphasias • Substitutions of non-correct sounds • Neologisms • Non-words being introduced as words • Possibility that grammatical structure selects for specific words within specific domains within the closed classes instead of as a whole • Activation of multiple meanings may be different in closed classes and open classes

28. Major Category Contrasts • Normal speech substitutions do not cross grammatical categories • Nouns substitute for Nouns, etc. • Wernicke’s Aphasia’s patients • Substitutions do not cross grammatical category

29. Nouns and Verbs • Categories can be lost in modality specific tasks • Ex: Two patients showed loss of verbs in oral output, but not in written • Agrammatics • More Loss of verbs in tasks across all modalities • Anomics • Disorder associated with dysfunction in “word finding” • No other disorder-frequent circumlocution • More loss of nouns across all modalities

30. Nouns and Verbs-IIWhat does it mean? • Anomics the failure may be at the word-form retrieval level • Agrammatics the failure may be at the phrasal construction or lemma level

31. Frequency and Grammatical Category Effects • Be/Bee wood/would • Show opposite effects for Broca’s vs. Wernicke’s aphasia regardless of frequency • Case study of Wernicke’s aphasia patient with no difference between high frequency and low frequency words • Possibly only affects open class words and not closed class words

32. Summary • The effects of aphasia illustrate some of the mechanisms of the lexical retrieval system • Specifically • Concept=>Lemma=>Phonological/Orthographic form • By studying aphasias we can understand how lexical retrieval works and what that means for lexical ambiguity