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Sensing and Perceiving Motion

This paper explores how motion is perceived through the analysis of spatio-temporal patterns using counterphase sinusoidal gratings. It discusses key elements such as the Reichardt detector, spatiotemporal filters, and the response characteristics of receptive fields in biological vision systems. The work highlights the importance of motion detection in evolutionary terms and differentiates between higher and early processing stages. Theoretical models, including the use of Gabor functions and energy models, are presented to explain the directionally specific responses of motion perception.

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Sensing and Perceiving Motion

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  1. Sensing and Perceiving Motion Cmput 610 Martin Jagersand 2001

  2. How come perceived as motion? Im = sin(t)U5+cos(t)U6 Im = f1(t)U1+…+f6(t)U6

  3. Counterphase sin grating • Spatio-temporal pattern • Time t, Spatial x,y

  4. Counterphase sin grating • Spatio-temporal pattern • Time t, Spatial x,y Ignoring Phi: = +

  5. Notes: • Only one term: Motion left or right • Mixture of both: Standing wave • Direction can flip between left and right

  6. QT movie Reichardt detector

  7. Gradient: in Computer Vision Correlation: In bio vision Spatiotemporal filters: Unifying model Severalmotion models

  8. Spatial response:Gabor function • Definition:

  9. Temporal response: Adelson, Bergen ’85 Note: Terms from taylor of sin(t) Spatio-temporal D=DsDt

  10. Receptor response toCounterphase grating • Separable convolution

  11. Simplified: • For our grating: (Theta=0) • Write as sum of components: = exp(…)*(acos… + bsin…)

  12. Space-time receptive field

  13. Combined cells • Spat: Temp: • Both: • Comb:

  14. Result: • More directionally specific response

  15. Energy model: • Sum odd and even phase components • Quadrature rectifier

  16. Adaption:Motion aftereffect

  17. Where is motion processed?

  18. Higher effects:

  19. Equivalence:Reich and Spat

  20. Conclusion • Evolutionary motion detection is important • Early processing modeled by Reichardt detector or spatio-temporal filters. • Higher processing poorly understood

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