You mean like in the Babylon 5 season 3 finale, where Sheridan jumps to his death on Z'ha'dum and is brought back to life to lead the alliance against the Shadows and Vorlons?

Oh wait, that's the opposite of what you were trying to say.

And Babylon 5 was the best SF to ever hit TV...

There are basically 5 types of cells in the retina: photoreceptors (rods & cones), bipolar cells, amacrine cells, horizontal cells, and ganglion cells.

Photoreceptors transmute light into electro-chemical signals with photopigments, bipolar cells link multiple photoreceptors in a lateral inhibition configuration and perform basic luminosity gradient/edge detection preprocessing. The amacrine and horizontal cells are involved in motion detection and image smoothing, but I don't know much about them. The bipolar cells doing edge detection feed into ganglion cells which connect to the optic nerve to send that signal to the visual cortex, which does more complex feature discrimination (bars, lines etc...).

There are separate ganglion cells which perform rate coded colour detection through what's called the opponent process. There are only two types: blue/yellow and red/green.

The red/green ganglia are easy to describe, they are excited by the red cone photoreceptors and inhibited by the green cone photoreceptors. These signals combine to determine the rate of firing of the ganglion cell. So lots of red light means the red/green ganglia fire rapidly, signalling we are seeing red. Lots of green light makes the red/green ganglia fire slowly or not at all, signalling we are seeing green.

The blue/yellow ganglia are a little more complex, they are excited by the red *and* green cone photoreceptors, and inhibited by the blue cone photoreceptors (synaptic weights from the cones to the ganglia are not equal). So lots of reg+green light = blue/yellow ganglia increase rate of firing signalling yellow, while lots of blue light = blue/yellow ganglia decrease rate of firing signalling blue.

Incidentally, this is why red & green and blue & yellow are "complementary" colours, and accounts for many afterimage effects (e.g. stare are something, then stare at a blank wall) - the retina can't physically signal red and green or blue and yellow at the same time.

The signal being sent along the optic nerve from the ganglia then consists of basically three channels: a luminosity gradient, red/green and blue/yellow. The specific ganglion sending the signal indicates where it was detected in retinotopic space. I am specifically leaving out the amacrine/horizontal cells here, I know they are involved somehow in signal modulation and motion detection, but again, I don't really know how that system works.

The preprocessing done by the retina on visual input can be broken down into three broad categories: edge detection, colour detection and motion detection. The retinal signal is then processed using what I like to call "magic" in the visual cortex to create our perceptions.

Hope this helps!