1. Movimento complesso: flusso ottica

2. Lettura Morrone, M.C., Burr, D.C., and Vaina, L. (1995). Two stages of visual processing for radial and circular motion. Nature 376, 507-509. Morrone, M.C., Tosetti, M., Montanaro, D., Burr, D.C., Fiorentini, A., and Cioni, G. (2000). A cortical area that responds specifically to optic flow, revealed by function Magnetic Resonance Imaging. Nature Neuroscience 3, 1322-1328. d'Avossa, G. et al. (2007). Spatiotopic selectivity of BOLD responses to visual motion in human area MT. Nat Neurosci 10, 249-255.

3. Neural response in MSTd Duffy & Wurtz, 1991

4. Psychophysical evidence for detection of optic flow in humans?

5. Spatial summation

6. Signal-to-noise Predictions S α N sectors σ 2 α N sectors σ α √N sectors S/σ α √N sectors

7. Spatial summation in noise

8. Signal-to-noise Predictions S α N sectors σ 2 = k (constant) S α N sectors

9. Spatial summation of contrast

10. Two-stage motion analysis Σ Local motion detectors Contrast thresholded Complex motion integrator

11. Spatial summation of contrast in noise

13. Temporal summation of contrast sensitivity

14. Motion coherence sensitivity 10 secs noise signal

15. Summation constants

16. Segmentation has different temporal integration. Even a weak signal embedded in noise can be seen given a long enough view

17. Summation with large fields

18. Summation with large fields in noise

19. Spatial summation for flow is extensive

20. Spatial summation of contrast sensitivity of sinusoids Anderson and Burr, 1987

21. Interim Conclusions There exists psychophysical evidence for detectors tuned to complex optical flow. Evidence suggest that the detectors are “second-stage” after contrast thresholding. Temporal summation is extensive: ~ 3 sec. Spatial summation is extensive, ~ 70°.

22. A neural centre for optic flow?

24. How Functional Magnetic Resonance Imaging (fMRI) Works: Brain Increased brain activity produces a local increase in blood oxygenation Physics Oxygenated and De- oxygenated blood have different magnetic properties MR images are brighter where there is greater brain activity

25. Unfolding Superior Lateral Superior Posterior 1 cm

26. Expanding ring V1 V2 V3

27. Rotating wedge V1 V2 V3

28. MT V1

29. Demo in dos Dos Demo

30. FLOW (30 s) NOISE (30 s) 2 s Inverting Direction Rotation Radial Translation

31. MT Time (s) Response Inverting Rotation / Inverting Noise Continuous Rotation / Noise Gradually Changing Flow / Noise MC b a c d e f

33. Translation Flow SB

34. Spatiotopic coding of visual motion in human MT

35. Two motion signals separated by delay Motion signals integrate spatiotopically across saccades Melcher & Morrone Nat. Neurosc. 2003

36. Percent correct Summation of motion signals one fixation two different fixations Two motion signals separated by delay

37. Integration of motion at threshold across saccades is spatiotopic Where in the human brain does the spatiotopic integration occur?

38. Cortex David Hubel and Torsten Wiesel: Spatially localized receptive fields in primary visual cortex

39. RETINOTOPIC MAP Tootel et al, Science, 1982 Monkey anatomy

40. RETINOTOPIA: Neuroni vicini della retina poiettano a Neuroni vicini della corteccia ‘Retinotopic’ visual areas

41. Each visual brain area contains a map of the visual world and performs a different function.

42. S1 S2 S3 S4

43. -4 0 4 FLOW - NOISE GDA Left VF – Right VF Left Hemisfere 15˚ 4.5˚ Human MT complex

44. Response is specific to controlateral stimuli

45. V1 No modulation of response by gaze

46. MT: Strong modulation of response by gaze

47. Gaze modulation of MT and V1 Central target Eccentric target D’Avossa et al. Nat. Neurosc. 2007

48. 2X8deg 7 deg S1 S2 S3 S4 D’Avossa et al. Nat. Neurosc. 2007 Block design: spatial selectivity with eccentric fixation F1F0F2

49. Spatial selectivity with central fixation

50. Spatial selectivity of BOLD responses in hMT is modulated by eye position D’Avossa et al. Nat. Neurosc. 2007

51. Spatial selectivity of hMT is invarient in external but not retinal coordinates. D’Avossa et al. Nat. Neurosc. 2007

52. Spatiotopicity of V1 and MT D’Avossa et al. Nat. Neurosc. 2007

53. Left MT

54. Indexes

55. Fig1

56. Fig 2

57. Fig 3

58. Fig 4

59. Conclusion A specific portion of the hMT complex shows spatiotopic tuning, suggestion that the transformation from retinal to external coordinates may occur within this structure. The spatiotopicity requires attention.

60. Experiment in dos Biological motion