1. What do we know about Primary Visual Cortex (V1) Xingyuan @swarma.net 2013.6.30

2. Visual Neural Pathways

3. Retinal Photoreceptors

4. Rods – have a high sensitivity to low levels of brightness – no rods in the fovea (around) Cones – three cone types allow for the perception of color – Most cones are concentrated in and around the fovea (center)

5. S and L Cones

6. LGN (Lateral geniculate nucleus)

7. Retina Ganglion Cells and LGN the information from the two eyes remains still entirely separate in six different neuronal layers there is even almost a one-to-one correspondence between retinal ganglion and LGN cells In motion analysis, LGN ganglion cells have lower optimal temporal frequencies

8. Responses of a Neuron in Cat Brain

9. Center-surround receptive fields

11. Difference of Gaussians

12. Difference of Gaussians On GIMP

13. The contrast sensitivity function

15. Single-opponent cells Single-opponent cells are color sensitive and compute color differences – namely L-M (L for long wavelength and M for middle wavelength, symbol “-” stands for oppo- nency) and S- (L+M) (S stands for short wavelength), thereby establishing the red-green and the blue-yellow color axes. These cells are parvocellular (P) neurons and are somewhat slower but have smaller receptive fields, i.e. higher spatial resolutions, than the magnocellular neurons.

16. Responses of V1 Neuron in Cat Brain

17. Tuning curves From Dayan and Abbott, Theoretical Neuroscience

18. Simple and Complex Cells

19. Other Cells in Area V1 edges, bars, gratings line endings motion color disparity

20. Why?

21. Faithful and efficient?

24. orientation selectivity

25. Competitive Learning

26. Self-Organizing Map: demo

27. Self-Organizing Map: MNIST

28. Self-Organizing Map: WORDS

29. Summary

30. Thank you! @ 淘幕天 _ 袁行远