color vision

Color vision

Outlines

• What is color

• Retinal circuitry for color vision

• Several ways to label retinal cells

Color history: discovery of color

Isaac Newton

Color history: discovery of color

Reflection makes colors

Retina anatomy of human being

Outer nuclear layer

Inner nuclear layer

Ganglion cell layer

Outer plexiform layer

Inner plexiform layer

Cone mosaic in human retina

L-cone M-coneS-cone

L-cone or M-cone

Immunohist-ochemistry

(IHC)S-cone

Immunohist-ochemistry

(IHC)

Trichromats vs Dichromats

Strategy to see color• Principle of Univariance: any single photopigment is “colour blind”. Given proper combination of wavelength and intensity, and can trigger same response in M-cone.

• Color-coding ganglion cells receive antagonistic input from cones: red-green; yellow-blue

Color opponency mechanism

Red-green opponent cells: midget ganglion cells

Blue-yellow opponent cells: small bistratified ganglion cells

Review by Dacey, 20001111

Dichromats

Review of Masland, 2012

S/M opponent ganglion cells in retina of guinea piga dichromatic mammal

Dye iontophoresis

To dye fill a cell: A. visualize the cell via quick and rough nucleus stainingB. A microelectrode filled with fluorescent dye is placed

carefully in contact with the somaC. Break into the cell and apply current. “injecting fluorescent

dye into the cell electronically”.D. How big is 10μm? The width (diameter) of a human hair

ranges from 0.017 to 0.181 mm.

Dye iontophoresisWhat is ?

Movie showing iontophoresis of dye into retinal ganglion cell

Summary of cell labeling techniques

1. Immunocytochemistry

2. Dye-filling

3. Genetic tags: GFP, YFP…

History of genetic tag: GFP

2008 Nobel prize winners Osamu Shimomura, Martin Chalfie, and Roger Tsien,

Genetic tags: YFP

Transgenic lines that mark RGC subtypes

“Most of my knowledge came from self-study,” says Dr. Shimomura. “If you find an interesting subject, study it through to the finish. If you confront difficulties, overcome them. Don’t be discouraged. There are always difficulties in research.”

The End