Download 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
– three cone types allow for the perception of color
– Most cones are concentrated in and around the
fovea (center)
S and L Cones
LGN (Lateral geniculate nucleus)
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
Responses of a Neuron in Cat Brain
Center-surround receptive fields
Center-surround receptive fields
Difference of Gaussians
Difference of Gaussians On GIMP
The contrast sensitivity function
The contrast sensitivity function
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.
Responses of V1 Neuron in Cat Brain
Tuning curves
From Dayan and Abbott, Theoretical Neuroscience
Simple and Complex Cells
Other Cells in Area V1
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edges, bars, gratings
line endings
motion
color
disparity
Why?
Faithful and efficient?
Faithful and efficient?
Faithful and efficient?
orientation selectivity
Competitive Learning
Self-Organizing Map: demo
Self-Organizing Map: MNIST
Self-Organizing Map: WORDS
Summary
Thank you!
@淘幕天_袁行远