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What do we know about Primary Visual Cortex (V1)

What do we know about Primary Visual Cortex (V1). Xingyuan @ swarma.net 2013.6.30. Visual Neural Pathways. Retinal Photoreceptors. Retinal Photoreceptors. Rods have a high sensitivity to low levels of brightness no rods in the fovea (around) Cones

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What do we know about Primary Visual Cortex (V1)

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

  2. Visual Neural Pathways

  3. Retinal Photoreceptors

  4. Retinal Photoreceptors • 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

  10. Center-surround receptive fields

  11. Difference of Gaussians

  12. Difference of Gaussians On GIMP

  13. The contrast sensitivity function

  14. 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?

  22. Faithful and efficient?

  23. 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

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