1. Sensing and Perceiving Motion Cmput 610 Martin Jagersand 2001

2. How come perceived as motion? Im = sin(t)U5+cos(t)U6Im = 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. Reichardt detector QT movie

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

8. Spatial response: Gabor function Definition:

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

10. Receptor response to Counterphase 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