Language and lateralization

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

2. Last week • We did some basic memory experiments • We tried to locate memory in the brain and to relate brain lesions to amnesia • We also explored executive functions in the frontal lobes

3. This week • We will look at: • Aphasia • Speech production and perception • Language, its origins • … and the brain • Lateralization • This covers chapters 8 and 9 (ends at page 369)

4. Examples of exam questions • What is the role of the hippocampus in memory? • Describe what to expect with patients who have bilateral lesions of the hippocampus. • Describe three different ways in which brain lateralization has been studied • Mention some reasons why speech perception is difficult

5. Neuroanatomical questions • Draw as accurately as possible where Broca’s and Wernicke’s areas are located? • Which part of the brain is anterior?

6. Broca’s aphasia

7. Wernicke’s aphasia

8. Relative location of language areas

9. Early model of language in the brain

10. Schematic model (oversimplified) Concepts Broca Wernicke

11. 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

12. Source-filter model of speech

13. Speech production

14. English vowels: formants

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

16. Speech perception is very difficult

17. Understanding language is even more difficult

18. Language is hierarchical and can be extremely ambiguous

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

20. From concept to speech signal

21. 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

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

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

24. 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

25. 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

26. Biological origins of language • Why do we have language? • Co-evolution of ‘memes’ or cultural products, which uses language as a carrier? • What is language?

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

28. Grammar may be innate

29. 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 sigar The man that you thought was old lit his awful sigar The man that you thought that your mother had seen lit his awful sigar et cetera

30. Creoles and the origins of language • Creoles are based on pidgins • A pidgin is not a uniform language • A pidgin is not a complete language • Creoles are strikingly similar all over the world • Creoles probably emerge in a single generation • Creoles emerge spontaneously

31. Hatian creole

32. 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

33. Conclusion: 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’

34. Where is language located in the brain?

35. PET data corroborate the lesion data

36. 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)

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

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

39. Lateralization of brain function

40. There are several ways to investigate brain lateralization • Split-brain patients • Amytal testing • Dichotic listening and other lateralized experimental procedures

41. Split brain patients offer important insights into lateralization

42. Communication between the hemispheres can be investigated

43. With amytal testing one hemisphere is anesthetized

46. Dichotic listening is a ‘normal’ experimental procedure

47. Left-brain may attend more to detail, righ-brain more to contour

48. Right brain is faster for global stimuli Left brain is faster for local stimuli

49. ‘Level of detail’ may be defined through spatial frequency

50. Next week... • Motor control • Population coding • Chapter 10