What do we know about Primary Visual Cortex (V1)

Xingyuan @swarma.net2013.6.30

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

• 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