Language and lateralization

1. Language and lateralization Lecture 5 (Chapters 8 and 9)

2. Categorical perception example:Speech sounds

3. Source-filter model of speech

4. What is speech? • Speech are modulated wave forms that are produced by a source (lungs and glottis) and filtered by the vocal tract and lips and cheeks

5. Speech production

6. English vowels: formants

7. o The position of the articulatory organs during production of the vowels ah and oh a

8. Speech perception is very difficult. It is also categorical.

9. ee aa Vowels tend to be perceived continuously

10. Consonants tend to be perceived in terms of known categories, such as ba, da, and ga.

11. Recognition of a letter is a process of constraint satisfaction LAP CAP CAB L.. C.. .A. ..P ..B

12. CALM:Categorizing And LearningModuleBy Murre, Phaf, & Wolters (1992)

13. Pictures derived from Adriaan Tijsseling athttp://pavlov.rutgers.edu/~adriaan/Soft/Poise/CALM/(after Murre, 1992)

14. Activation rule

15. Learning rule

16. ParameterCALM Up weight 0.5 Down weight -1.2 Cross weight 10.0 Flat weight -1.0 High weight -0.6 Low weight 0.4 AE weight 1.0 ER weight 0.25 wµE0.05 k0.05 K1.0 L1.0 d0.01 Parameters Possible parameters for the CALM module They do not need to adjusted for each new architecture

17. Main processes in the CALM module

18. Language • What is language? • Is it innate or learned? • Where located in the brain? • Can neural networks represent language processes?

19. What is language? • De Saussure distinguished ‘langue’ from ‘parole’ • Chomsky distinguished ‘competence’ from ‘performance’ • Chomsky strongly defended the idea of the innateness of language

20. Language is hierarchical and can be extremely ambiguous

21. Grammar may be innate

22. The essence of grammar is recursion It allows an infinite number of sentences to be generated by just a few rules Simple grammar G = {N,V,S,P} S aSa S bSb S c E.g., c, aca, bcb, aacaa, aabacabaa S Þ aSa Þ aaSaa Þ aabSbaa Þ aabaSabaa Þ aabacabaa The man lit his awful cigar The man that you thought was old lit his awful cigar The man that you thought that your mother had seen lit his awful cigar et cetera

23. Where does language come from? • Certain aspects of the development of language and thought appear to be universal in that they • (i) preceed any learning by the individual • (ii) are found in all individuals in the same way • These universalia are often of a deep and abstract nature • It is not known at present how they are respresented in the brain, or how they emerge from brain organization

24. Universal constraints in thought development • Spelke shows that from a very early age, infants know about the continuity and solidity of objects • These constraints lie at the core of the developmental learning system • It is not clear how these are represented in the brain or how they emerge

25. Selection versus instruction • Chomsky/Pinker: The child must select a grammar • Bickerton: The child is provided with a specific grammar, which it than modifies in the direction of the caretaker’s language

26. Bickerton: Not all languages may be equally hard to learn • Children’s errors when learning English often resemble Creole, for example, the so called double negative • Perhaps, Creole is the ‘original mother language’

27. Relative location of language areas in the brain

28. Early model of language in the brain

29. Schematic model (oversimplified) Concepts Broca Wernicke

30. Willem Levelt’s model of speech production and perception

31. From concept to speech signal

32. Very complicated transformation take place during speaking • A conceptual representation is a network of neurons that fire with a complex associative correlational pattern • This conceptual-semantic pattern is transformed into a hierarchical syntactic pattern • This pattern is transformed into a serial speech pattern

33. Semantic networks may be used to help think about the associative networks in the brain

34. Better is it to view concepts as vectors of abstract ‘features’

35. Where is language located in the brain?

36. PET data corroborate the lesion data

37. How can semantic organization be organized according to category? • Self-organizing maps in the brain can explain the emergence of topological mappings • Examples are: • the somatosensory homunculus (discussed in lecture 7) • retinotopic maps in V1 (area 17, discussed in lecture 3)

38. Semantic organization can emerge on the basis of word context (Ritter and Kohonen, 1990)

39. Example of a semantotopic map Interesting is that words organize into both semantic and grammatical categories