1. Dominant Hemisphere Identification Handedness –tells us likelihood of LH being dominant (i.e., location of speech center) 96% in right handers 70-85% in left handers Behavioral tests Functional neuroimaging Clinical tests – Wada, TMS

3. Language Processing Speaking a written word involves at least five neocortical areas. Each area performs certain functions

4. Brain areas involved in Language

6. Visual Pathway

8. Lateralized Eye Movements Three synonyms for walking or intelligence Define impish or prudish Which direction does Thomas Jefferson face on the nickel? Which states share a border with North Carolina?

9. Lateralized Eye Movements – Interpreting LEMs Leftward movement from viewer’s perspective indicates LH activation (RVF squashed as LH taxed) Rightward mvt = RH location of function

10. Gross Laterality Tests Comparative (primary) tasks –Differences to lateralized presentations Accuracy and reaction time to emotional matching, abstract words, etc Competitive (secondary) tasks –Finger tapping during math, emotion, language tasks –Dowel balancing task

11. Tapping during nursery rhyme

14. Laterality of Auditory Processing Selectively deliver to one hemisphere but suppressing ipsilateral pathway

15. Monoaural vs Dichotic Listening With dichotic input the ipsilateral ear’s input is suppressed.

18. Left ear advantage for melodies, right ear advantage for shadowing spoken letters

19. Dichotic Listening Results Right Ear Adv –Digits –Words –Nonsense syllables –Morse code –Pitch changes in Thai by Thais –Voicing & Place –Difficult rhythms –Ordering temporal information –Backward speech Left Ear Advantage –Melody –Musical chords –Environment Sounds –Emotional Sounds –Prosody –Complex Pitch changes No advantage –Rhythms –Vowels

20. Dichotic Listening in Unusual Cases Genie (neglected/linguistically deprived) shows a left ear (RH) advantage for words Right hemispherectomy show normal right ear (LH) advantage for syllables Split brains show normal right ear advantage for digits

21. Hemisphericity Does one hemisphere dominate individual’s cognition or cognitive style?

22. Street Test of Right Hemisphere Dominance

26. Mooney (1957) – ID age & gender

29. Left hemisphere dominance

31. Similarities Test (selected items) Orange Coat Wagon Wood Egg Poem Fly Banana Dress Bicycle Alcohol Seed Statue Tree

32. Thompson, Bogen, Marsh, 1979 Industrial cultures LH>RH Non-industrial cultures RH>LH

38. Gazzaniga’s Interpreter Model

39. LECTURE 7 Homotopic Callosal Connections

40. Equipotentiality hypothesis vs homotopic principle

41. EEG site pairings

42. Callosal Connections

43. Principle of Callosal Homotopy The general principle of callosal homotopymthat the corpus callosum unites "corresponding and identical regions" (Meynert, 1872, p. 405), was initially proposed by Arnold (1838-1840) in his anatomy tables and later popularized by Meynert (1872). Bruce (1889-1890) criticized Meynert's endorsement, calling it speculation and opinion, ungrounded in physiological fact. Bremer (1958), however, continued to advance this principle, based on the anatomical and electro- physiological research of his day (Curtis, 1940a,b).

44. Principle of Callosal Homotopy CITATIONS Arnold, F (1838-1840). Tabulae anatomicae. London: Black & Armstrong. Bremer, F. (1958). Physiology of the corpus callosum. Research Publications for the Assessment of the Nervous and Mental Disability, 36, 424-428. Bruce, A. (1889-1890). On the absence of the corpus callosum in the human brain, with description of a new case. Brain, 12, 171-190. Curtis H.J. (1940a). Intercortical connections of > corpus callosum as indicated by evoked potentials. Journal of Neurophysiology, 3, 407-413 Curtis H.J. (1940b). An analysis of cortical potentials mediated by the corpus callosum. Journal of Neurophysiology, 3, 414-422. Meynert T (1872). The brain of mammals. In S. Stricker (Ed.) Manual of human and comparative histology, Vol II, (pp 367-537). London: The New Syndenham Society.

46. Principle of Homotopy Four types of cortico-cortical projections: 1) homotopic, 2) homoareal, 3) heterotopic, and 4) ipsilateral Arnold (1838-1840) – Anatomical tables – first mention of callosal homotopic connectivity Myers (1850s) – popularized homotopic principle Bremer (1956) – “general principle of homotopy” based on Curtis (1940;1944) electrophysiological studies

47. Reciprocity in Callosal Connections Representation of the reciprocity of callosal connections: strong homotopic connectivity, and wherever there is heterotopic connections, there is normally ipsilateral connections to the same areas.

49. Callosal Function Models 1. Transfer of information 2. Inhibition of opposite side processing 3. Homotopic inhibition, generating complementary percepts

50. Conduction Time

51. Conduction Time in Split Brains

52. Anatomical asymmetry LH contains –more gray matter Larger cells and greater cell density (but not all areas), more nonmyelinated fibers esp. frontally, suggesting more localized, more serial processing RH contains –More white matter more myelinated axons to link different brain regions –slightly larger and heavier than LH

53. Cell Density differences Human SMG (posterior language areas)

54. Larger LH pyramidal cells in Superior Temporal Gyrus HOWEVER asymmetry is not found in nearby angular gyrus

55. Homotopic inhibition theory

56. Priming explained

57. LECTURE 8 Functional Dichotomies

58. Aphasia by handedness & hemisphere damaged Right handed: LH 60%, RH 2% Left handed: LH 32%, RH 24%

59. Split Brain Patients PRE OPERATIVE POST OPERATIVE RIGHT HAND LEFT HAND RH superiority on Block design RH superiority on Drawing tasks

60. Local-global stimuli used to investigate hierarchical representation

61. Facilitatory effect for global-local stimuli

63. STUDY INTACT BRAINS Visual Laterality Method Tachistoscopic presentation (less than 200 ms) –Lateralized stimulus exposure –Compare performance LVF vs. RVF presentations. –Dependent variables: reaction time, accuracy

64. Methodology Issue 2 @ 2 = 3 or 4 2 @ 3 = 6 or 8 2 @ 4 = 8 or 16 Analysis of correct responses only

65. Functional Dichotomies BlackburnIntellectualSensuous OppenheimerTime, HistoryEternity, Timelessness Levy, SperryAnalyticGestalt BogenPropositionalAppositional LuriaSequentialSimultaneous SemmesFocalDiffuse I Ching The Creative: Heaven, Masculine, Yang The Receptive: Earth, Feminine, Yin Many sourcesVerbalSpatial Many sourcesIntellectualIntuitive JungCausalSynchronicity BaconArgumentExperience

66. Left Hemisphere Verbal Sequential, temporal, digital, routinized Logical, analytic Familiar Propositional Right Hemisphere Nonverbal, visuospatial Simultaneous, spatial, analogical, parallel, integrative Gestalt, holistic, synthetic Novelty Appositional