Theories of Language

1. Theories of Language • Mental lexicon: store of language information • Semantic (word meaning) • Syntactic (word combination) • Word form (spelling and sound pattern) • Phonological (sound-based) • Phoneme: smallest unit of sound in a language that has meaning • Older, evolutionary-based • Orthographic (vision-based) • Newer, object-based

2. Theories of Language • Lexicon organization (Levelt's, 1994, model) • Hierarchical, information-specific networks • Conceptual: semantic knowledge of word/meaning relations • Lemma: syntactic, grammatical • Lexeme: sound form

3. Theories of Language • Conceptual organization (e.g. Collins & Loftus, 1975, semantic network model) • Categorical networks of conceptual nodes • Semantic priming studies • Truck:Car vs Truck:Tulip

4. Theories of Language • Conceptual organization • How many conceptual systems? • Warrington's physical (living objects) vs functional (man-made objects) properties • Caramazza's animate-inanimate categories

5. Theories of Language • Conceptual organization • How many conceptual systems? • How many levels? • Damsio's category-specific deficits in object naming • Failures at lexical level

6. Theories of Language • Components of a language analysis system

7. Theories of Language • Components of a language analysis system • Spoken input • Phoneme analysis • Voicing • Vocal chords for and some consonants (e.g., b, m) • Point of articulation • Lips (b) • Lips and mouth (f) • Manner of articulation • Blocked airstream (p) • Unblocked airstream (l) • Physical boundaries • Prosody: rhythm • Stress

8. Theories of Language Components of a language analysis system • Spoken input • Neural substrate • Superior temporal gyrus • Wernike's area in LH • Ventrolateral superior temporal sulcus

9. Theories of Language Components of a language analysis system • Spoken input • Written input • Phoneme (alphabetic) systems: letters represent sounds • Shallow orthography: close correspondence between letters and sounds (e.g., Spanish) • Deep orthography: lack of correspondence between letters and sounds (e.g., English) • Syllabic systems: characters represent sounds (e.g., Kana) • Logographic systems: characters represent words (e.g., Chinese, sort of)

10. Theories of Language Components of a language analysis system • Spoken input • Written input • Feature analysis: "what" pathway • Modular models: bottom-up processing • Selfridge (1959) pandemonium model • Interactive models: top-down can influence bottom-up • McClelland and Rummelhart (1981) connectionist model

11. Theories of Language Components of a language analysis system • Spoken input • Written input • Feature analysis: "what" pathway • Modular models: bottom-up processing • Selfridge (1959) pandemonium model • Interactive models: top-down can influence bottom-up • McClelland and Rummelhart (1981) connectionist model • Word superiority effect supports interactivity • Respond "t" or "k" • Trip • t • Pirt

12. Theories of Language Components of a language analysis system • Spoken input • Written input • Neural substrate • Feature-level analysis same as object recognition • Letters activate occipitotemporal sulcus compared to faces (Puce et al., 1996) • Pure alexia: damage to occipitotemporal areas can result in reading deficit with otherwise normal language

13. Theories of Language Components of a language analysis system • Spoken/Written input • Word Recognition • Lexical access • Lexical selection • Lexical integration

14. Theories of Language Components of a language analysis system • Spoken/Written input • Word Recognition • Lexical access: differs for spoken and written input • Dual-route for written • Assembled: grapheme-to-phoneme • Direct: whole-word orthographic • Alexia without agraphia: deficit in reading, but not in comprehending or writing • Deep or phonological dyslexia: cannot read pseudowords that are not in lexicon, make semantic errors (direct route) • Surface dyslexia: rule-based speech (assembled route) translates letters to sounds

15. Theories of Language Components of a language analysis system • Spoken/Written input • Word Recognition • Lexical access: differs for spoken and written input • Dual-route for written • Temporal for spoken • Cohort model (Marslen-Wilson, 1980): phoneme analysis activates cohort of matching words until best match is selected

16. Theories of Language Components of a language analysis system • Spoken/Written input • Word Recognition • Neural substrate • Hierarchical model (Binder at al., 2000) • Primary auditory cortex (Heschl's gyri) to STG: no differential of speech sounds • STG to superior temporal sulcus: speech distinguished from nonspeech, but no lexical/semantic distinction (activated by speech, backward speech, nonwords) • STS to MTG, inferior temporal gyrus, angular gyrus, temporal pole (more LH than RH): words distinguished from nonwords

17. Theories of Language Components of a language analysis system • Spoken/Written input • Word Recognition • Sentence integration: higher-order processes • Semantic and syntactic integration • Grammatical structure

18. Theories of Language Components of a language analysis system • Spoken/Written input • Word Recognition • Sentence integration: higher-order processes • Semantic and syntactic integration • Grammatical structure • Parser: process by which sentences are decomposed into syntactic units • Garden-path model (Frazier, 1987): syntactic nodes have preferred structure based upon economy (minimal attachment and late closure), modular model doesn't allow for context

19. Theories of Language Components of a language analysis system • Spoken/Written input • Word Recognition • Sentence integration: higher-order processes • Semantic and syntactic integration • Grammatical structure • Parser • Garden-path model (Frazier, 1987) • Parsing is an interactive process (Münte et al., 1998): temporal organization of sentence affects processing

20. Theories of Language Components of a language analysis system • Spoken/Written input • Word Recognition • Sentence integration • Neural substrate: Broca's area • Agrammatic aphasia: deficit in producing and understanding complex grammatical structure after lesion in Broca's area

21. Theories of Language Components of a language analysis system • Spoken/Written input • Word Recognition • Sentence integration • Neural substrate: Broca's area • Agrammatic aphasia • PET studies (e.g., Caplan et al., 2000) find activation in Broca's area for normals when processing complex ("The juice that the child enjoyed stained the rug.") vs simple ("The child enjoyed the juice that stained the rug.") grammers.

22. Theories of Language Components of a language analysis system • Spoken/Written input • Word Recognition • Sentence integration • Neural substrate: other areas • Wernicke's (and Broca's) area and homologous RH locations (Just et al., 1996) • Processing meaningful stories activates rCBF in the left middle temporal gyrus, the left and right temporal poles, and a superior prefrontal area in the left frontal lobe, but only the temporal poles remain activated whenever sentences with acceptable syntax and prosody are presented. (Mazoyer et al., 1993)

23. Theories of Language Speech production system (Levelt's model) • Conceptual level • Macroplanning: communicative intent, planning goals of communication • Microplanning: planning word choice and grammar to convey intent • Lemma level • Formulator: process of getting message into grammatical and phonological form • Lexeme level • Mapping phonemes to motor program

24. Theories of Language Speech production system • Neural substrate • Dronkers et al. (1996) Compared brain lesions of 25 stroke patients (aged 32-79 yrs) with apraxia of speech with lesions of 19 stroke patients (aged 52-80 yrs) without such deficits to determine brain regions potentially involved in coordinating speech. A robust double dissociation was found between the 2 groups. All Ss with articulatory planning deficits had lesions that included a discrete region of the left precentral gyrus of the insula, a cortical area beneath the frontal and temporal lobes. This area was completely spared in all Ss without these articulation deficits. Thus, this area seems to be specialized for the motor planning of speech.

25. Neuropsychology of Language Aphasia: disorders of language comprehension and production following neurological insult • Primary aphasia: problems with language processes • Secondary aphasia: problems with attention, perception, or memory that affect language (e.g., alexia) • No animal models for language, so most of what is known about the localization and structure of language systems comes from patient studies

26. Neuropsychology of Language • Classical localization model of language system • Broca's area: LH inferior frontal lobe (areas 44 & 45) • Damage produces deficits in language production (Broca's or expressive aphasia)

27. Neuropsychology of Language • Classical localization model of language system • Broca's area • Wernicke's area: LH posterior STG • Damage produces deficits in language comprehension (Wernicke's or receptive aphasia)

28. Neuropsychology of Language • Classical localization model of language system • Broca's area (M): word production - speech planning and motor programming • Wernicke's area (A): word comprehension - storage of phonological lexicon • Conceptual area (B): word representation - widely distributed (e.g., supramarginal and angular gyri)

29. Neuropsychology of Language • Evidence for the classical localization model • Damage to arcuate fasciclus between M and A produces deficits in repeating and producing speech but not in comprehension (conduction aphasia) • Damage to fiber tract between B and A produces deficits in comprehension but not in repeating and producing speech (transcortical sensory aphasia)

30. Neuropsychology of Language • Limitations of the classical localization model • Not all patients that have damage to Broca's or Wernicke's areas show classic deficit • Classic model fails to fully account for contributions of subcortical structures and damage to fiber tracts • Comprehension often improves with time after damage to Wernicke's area • Damage also produces anterograde and retrograde degeneration in other areas • Anatomical location of focal lesion may not capture function loss in brain metabolism

31. Neurophsyiology of Language • Semantic integration: N400 • Large N400 with difficult semantic integration

32. Neurophsyiology of Language • Semantic integration: N400 • Syntactic processing: P600/SPS • Syntactic positive shift with violations of grammer

33. Neurophsyiology of Language • Semantic integration: N400 • Syntactic processing: P600/SPS • Syntactic positive shift with violations of grammar • Syntactic processing: LAN • Left anterior negativity with violations of noun-verb relations