1. Spatial representation and parietal cortex Marlene Behrmann Department of Psychology, CMU and CNBC Contact: behrmann@cnbc.cmu.edu 268-2790 URL: http://www.cnbc.cmu.edu/~behrmann

3. Division of labour in human visual cortical system

4. Mishkin and Ungerleider

8. The parietal lobes: “crossroads of the brain” (Critchley, 1953) well situated topographically multimodal requisite cortical and subcortical connectivity Distribution of MCA, little collateral supply Inferior Parietal lobule Supramarginal gyrus Angular gyrus

9. Neglect

10. Federico Fellini (1920-1993)

11. * Asymmetry in incidence: RH (66%) in humans not monkeys Inferior parietal lobule –Areas 39 and 40; –non-human primate analog: IPL (7) vs STS –bimodal: short-lived vs persistent Affects different sensory modalities Not sensory deficit * Neglect

12. Not just parietal Distributed network: (Mesulam; Heilman) –dorsolateral prefrontal, medial frontal (cingulate, thalamus, basal ganglia, white matter). –Same network activated in eye movement studies Close relationship between attention and eye movements (Corbetta et al.) Other terminology –Extinction –Allesthesia –anosagnosia

13. Extent of effect Other sensory modalities –Auditory –Olfactory –Tactile Mental imagery –Piazza del Duomo (Bisiach and Luzzatti) Affects output: not surprisingly

14. Vision and eye movements (Behrmann et al.) 45 x 36 degrees visual angle magnetic scleral coil in right eye indicate number of As in display

15. Lesions: neglect patients

16. Lesions: BD controls with hemianopia

17. Location and duration of fixations

18. Eye movements reflect left-sided neglect

21. What can we learn about parietal cortex? What determines what information is neglected? What gives rise to neglect? What happens to the information that is neglected?

22. What can we learn about parietal cortex? What determines what information is neglected? What gives rise to neglect? What happens to the information that is neglected?

23. Possible frames of reference: what defines ‘left’?

24. Visual neglect in allocentric coordinates

26. Depiction of environmental neglect

27. Visual neglect in allocentric and egocentric coordinates

28. Tactile and visual neglect Moscovitch and Behrmann

29. Tactile neglect in allocentric co-ordinates

30. Range of possible frames of reference

31. Neglect with respect to object midline Target Copy

32. Behrmann and Tipper right object right space left object right space

33. Object-based neglect: inhibition for right and facilitation for left targets

34. Directional selectivity of neurons Olson and Gettner (1995, 1998) L/R of bar L/R eye movement

35. Neurons fire for left or right of bar independent of direction of movement

36. Paradigm: object and environ- neglect square circle

38. Simultaneous object- and environ-based neglect

39. Multiple reference frames in eye movements too

40. Normal: no errors in reading

41. Neglect: errors and eye movements

42. Another example

43. Hemianopic: no reading errors

44. Frames of reference Egocentric (dependent on viewer) But also allocentric (independent on viewer) –Not only in vision, also in tactile Multiple coordinate frame –Also evident in eye movements

45. What can we learn about parietal cortex? What determines what information is neglected? What gives rise to neglect? What happens to the information that is neglected?

46. What gives rise to neglect? gradient Gradient consistent with neuronal distribution: 68 bilateral, 29 contra, 3 ipsi

47. Suggests competition too: bad on left, too good on right

48. Visual search paradigm

49. Normal subjects

50. Patients with LHD

51. Patients with RHD

52. So: Spatial deficit apparent in visual search Generally scaled with severity of neglect –But more in RHD than LHD –Some competition: better on right side as neglect severe in conjunction

53. What can we learn about parietal cortex? What determines what information is neglected? What gives rise to neglect? What happens to the information that is neglected?

54. Fate of neglected information Do patients process unattended information normally? –failure to reach consciousness? –degraded processing?

55. Volpe, Ledoux and Gazzaniga (1979) Same or different?Name the objects Response: differentResponse: A star Unconscious processing/ failure to explicitly report information that is available

57. Priming paradigm McGlinchey Berroth et al. Normal subjects: faster lexical decision time if related than unrelated related unrelated GOSE THIP

58. Results Patients faster to say ‘yes’ when semantic related pic on right (eye-nose) compared to eye-ship Patients faster to say ‘yes’ when semantic related pic on left SAME AMOUNT OF PRIMING/FACILITATION FROM BOTH SIDES! Even though report the information. Patients process neglected info normally.

59. Results … Continued BUT: normals show double priming on left than right Cannot conclude processing is normal! Priming not as demanding as explicit report.

60. What can we learn about parietal cortex? What determines what information is neglected? –Multiple reference frames, demands of task What gives rise to neglect? –Competition between residual activated neurons, spatial and temporal factors relevant What happens to the information that is neglected? –Seems to be activated to some extent, not fully

61. Alternative view of parietal cortex: “how” not “where” Milner and Goodale –Parietal cortex involved in on-line ballistic movements Where the action is!

64. Grasping

65. matching

67. What can we learn about parietal cortex? What determines what information is neglected? –Multiple reference frames, demands of task What gives rise to neglect? –Competition between residual activated neurons, spatial and temporal factors relevant What happens to the information that is neglected? –Seems to be activated to some extent, not fully