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La percezione del movimento

La percezione del movimento. La selettività neurale per il movimento. Il detettore (parziale) di Reichardt. Nulla. Preferita. Il detettore (completo) di Reichardt. Movie. L ’ illusione dell ’ insegna dei barbieri. demo. V1. MT. Waterfall illusion (Addams, 1834).

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La percezione del movimento

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  1. La percezione del movimento

  2. La selettività neurale per il movimento

  3. Il detettore (parziale) di Reichardt Nulla Preferita

  4. Il detettore (completo) di Reichardt Movie

  5. L’illusione dell’insegna dei barbieri

  6. demo

  7. V1 MT

  8. Waterfall illusion (Addams, 1834)

  9. Positional motion aftereffect (PMAE) Snowden (1998) Curr. Biol. Nishida & Johnson (1999) Nature

  10. Movimento complesso: flusso ottica

  11. Lettura • Morrone, M.C., Burr, D.C., and Vaina, L. (1995). Two stages of visual processing for radial and circular motion. Nature376, 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 Neuroscience3, 1322-1328.

  12. Neural response in MSTdDuffy & Wurtz, 1991

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

  14. Spatial summation

  15. Signal-to-noise Predictions • S α Nsectors • σ2α Nsectors σα √Nsectors • S/σα √Nsectors

  16. Spatial summation in noise

  17. Signal-to-noise Predictions • S α Nsectors • σ2= k (constant) • S α Nsectors

  18. Spatial summation of contrast

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

  20. Spatial summation of contrast in noise

  21. Spatial summation of contrast in noise

  22. Temporal summation of contrast sensitivity

  23. 10 secs Motion coherence sensitivity signal noise

  24. Summation constants

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

  26. Summation with large fields

  27. Summation with large fields in noise

  28. Spatial summation for flow is extensive

  29. Spatial summation of contrast sensitivity of sinusoidsAnderson and Burr, 1987

  30. 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°.

  31. A neural centre for optic flow?

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

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

  34. Translation Flow SB

  35. Experiment in dos Biological motion http://www.biomotionlab.ca/Demos/BMLwalker.html

  36. Adult plasticity: paraplegia affects perception of “biological motion” The mirror system? (Giacomo Rizzolatti)

  37. Sensitivity impaired for biological motion but not contrast sensitivity for orientation Controls Patients Arrighi et al., Current Biol. (2011)

  38. Paraplegic sensitivity worse for visual motion, especially biological motion Arrighi et al., Current Biol. (2011)

  39. The results point to shared neural circuits for production and perception of movement – the mirror system?

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