16: Color Constancy

What is the midget pathway good for?

High spatial resolution

What cells regulate R/G color vision?

Midget bipolars

How do midget bipolar cells regulate R/G vision?

Because each midget bipolar only contacts 1 cone (M or L)

Using a red or green diffuse light, the center wins out for a midget cell when…

The color shone matches the spectral sensitivity of the cone (M or L) in the center

Using a red or green diffuse light, the center wins out for a parasol cell when…

Always (no color opponency)

Where do S-cone bipolars synapse?

Onto bi-stratisfied RGC in the IPL close to the GCL

The bi-stratisfied RGCs connect to what on each end? Where do these synapses occur

Closer to the GCL: connect to an ON S-cone bipolar

Closer to the INL: connect to a diffuse OFF bipolar (that receives input from L and M cones)

How do bi-stratisfied RGCs work?

Red/green/yellow light: OFF response

Blue light: ON response

What is the wavelength cutoff where a bistratisfied RGC will depolarize or hyperpolarize?

Depolarize under 500

Hyperpolarize over 500

What do midget RGCs signal for our vision?

Detailed pattern information and red-green color

What opponency do midget RGCs show?

Spatial and chromatic

What opponency do bistratisfied RGCs show?

Chromatic only

What opponency do parasol RGCs show?

Spatial only

What are the spectral peaks for midget RGCs

520 and 600

What are the spectral peaks for bistratisfied RGCs

440 and 555

What are the spectral peaks for parasol RGCs

555

Center-surround antagonism is responsible for what visual processes/aspects?

Spatial vision

Red/green color vision

Contrast

What is the zone/stage model of color vision?

Combines the Young-Helmholtz trichromacy theory (3 types of cones) and Hering color opponent theory and says there are 2 zones/stages of color processing

What is the first zone of the zone model of color vision?

Says there are 3 cone types (S, M, L)

What is the second zone of the zone model of color vision?

Says that the output from the 3 cones is combined into different opponent and non-opponent channels