1. Central Auditory Pathways, Functions, and Language Central Auditory Pathways, Functions, and Language

2. What can we hear?

3. Subcortical auditory pathways

4. 8 th nerve (vestibulocochlear )

6. brachium of the inferior colliculus lateral lemniscus

7. Sound Localization

8. Cue 1: Delay between time of sound arrival at left and right ears (speed of sound in air = 342 m/sec)

9. Cue 2: Sound is louder in one ear than the other

10. cochlear nuclei superior olive lateral lemniscus

11. Superior olive, human superior olive

12. axon “rabbit-ear” neuron Stotler 1953 in cat MSO

13. axon “rabbit-ear” neuron axons from right cochlear nuclei axons from left cochlear nuclei Stotler 1953 in cat MSO

14. delay spikes by 250 microsec

16. Do animals with big heads localize sound more accurately?

17. Head size weakly correlated with sound localization precision r = -0.425 Heffner 1997

19. Density of retinal ganglion cells, 3 species Heffner 1997

20. Width of high acuity visual field is strongly correlated with sound localization precision r = 0.92

21. MGN (medial geniculate nucleus)

22. Left hemisphere, cutaway view temporal lobe AI (primary auditory cortex = transverse temporal gyrus)

23. low best frequencies high best frequencies tonotopic map in AI

24. cochlear nuclei superior olive MGN (medial geniculate nucleus) inferior colliculus The auditory system is only partially crossed

25. AI Primary auditory cortex

26. After lesion of AI … Can still identify sounds Can understand speech reasonably well Poor localization of sound in contralateral half of space

27. After lesion of AI … Can still identify sounds Can understand speech reasonably well Poor localization of sound in contralateral half of space

28. Beyond A1…Language areas

29. Left hemisphere, cutaway view temporal lobe AI (primary auditory cortex = transverse temporal gyrus) Beyond A1…Language areas

30. Broca’s aphasia (expressive aphasia): difficulty in speaking or writing Wernicke’s aphasia (receptive aphasia): difficulty in understanding speech or written material

31. Broca’s area lesions

32. Broca’s aphasia (expressive aphasia): difficulty in speaking or writing Wernicke’s aphasia (receptive aphasia): difficulty in understanding speech or written material

33. Wernicke’s area lesions

34. Wernicke’s area Broca’s area angular gyrus

35. Functional imaging studies show a different picture

36. Wernicke’s area Broca’s area angular gyrus Activating Wernicke’s area in fMRI experiments

37. fMRI responses to pure tone task Binder…Prieto, 1997

38. fMRI responses to language task

39. angular gyrus regions activated specifically by listening to words angular gyrus Broca’s area Wernicke’s area Binder et al. 1997

40. angular gyrus Broca’s area Wernicke’s area regions activated specifically by listening to words Binder et al. 1997

41. premotor cortex angular gyrus primary motor cortex Broca’s area Binder et al. 1997

42. scrambled sentence: And disappeared the bushes rabbit down the into bounded hill the meaningful sentence: The rabbit bounded down the hill and disappeared into the bushes From words to sentences…

43. scrambled sentence: And disappeared the bushes rabbit down the into bounded hill the meaningful sentence: The rabbit bounded down the hill and disappeared into the bushes From words to sentences…

44. scrambled sentence: And disappeared the bushes rabbit down the into bounded hill the meaningful sentence: The rabbit bounded down the hill and disappeared into the bushes activity when reading meaningful sentences minus activity when reading scrambled sentences Extracting meaning from sentences

45. lesions cause problems in naming objects or people (anomic aphasia)

46. Some areas in left hemisphere used in language processing

47. Where are language areas in deaf people who communicate with sign language?

48. Petitto et al. 2000 Normal subjects, activation by reading “horse”, responding “gallop” Subject #1 Subject #2

49. Normal subjects, activation by reading “horse”, responding “gallop” Petitto et al. 2000 Subject #1 Subject #2

50. Deaf subjects, view signs for “horse”, respond with signs for “gallop” Petitto et al. 2000

51. In deaf people who communicate with sign language, Broca’s area helps produce signed speech

52. Deaf subjects: view signs for “horse”, respond with signs for “gallop” Petitto et al. 2000

53. In deaf people who communicate with sign language, auditory cortex helps out with language processing