No – significant preprocessing of photoreceptor cell signals occurs in the eye, in the retina. The "raw" signals from the three cone types are processed into luminance and two color-opponent channels before being sent to the visual cortex. (While there are around 130 million retinal receptors, there are only approximately 1.2 million axons bundled in the optic nerve.)
Actually they do, and beyond that, the retina contains neurons that do the basic processing before travelling down the optic nerve to the brain. The retina is also basically brain tissue and is part of the central nervous system.
Indeed, among other things, they detect edges, movement, and preprocess color from RGB to something conceptually closer to YUV (with color encoded along two contrast axes: red-green and blue-yellow).
To reinforce what you're saying, I just want to point out that the retina is actually a part of the central nervous system. It grows from the same tissue that the brain does during fetal development.
I would compare the kind of "eye" that these bacteria are more to the parietal eye: it detects light to allow movement toward that light (in the Cyanobacteria, to photosynthesize; in primitive animals, likely to find and eat the Cyanobacteria!)
I almost wonder if the genetic code for the parietal eye + pineal gland looks anything like the code for this bacteria's shell. There could be a continuous line of descendence, there.
pluteoid|10 years ago
gnaritas|10 years ago
pygy_|10 years ago
https://en.wikipedia.org/wiki/YUV
SapphireSun|10 years ago
derefr|10 years ago
I almost wonder if the genetic code for the parietal eye + pineal gland looks anything like the code for this bacteria's shell. There could be a continuous line of descendence, there.