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What do we know about Primary Visual Cortex (V1) 2013.6.30.

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Presentation on theme: "What do we know about Primary Visual Cortex (V1) 2013.6.30."— Presentation transcript:

1 What do we know about Primary Visual Cortex (V1)

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

10

11 Difference of Gaussians

12 Difference of Gaussians On GIMP

13 The contrast sensitivity function

14

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

23

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 淘幕天 _ 袁行远

31


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