Color vision which is true: (AIIMS May 2009)
|A||Independent of wave length of light|
|B||Involves opponent color cells|
|C||Minimum at fixation point|
|D||Depends on intensity discrimination|
1. Color processing begins at a very early level in the visual system (even within the retina) through initial color opponent mechanisms.
2. Opponent mechanisms refer to the opposing color effect of red-green, blue-yellow, and light-dark. Visual information is then sent back via the optic nerve to the optic chiasm.
3. After the optic chiasm the visual fiber tracts are referred to as the optic tracts, which enter the thalamus to synapse at the lateral geniculate nucleus (LGN).
4. The LGN is segregated into six layers: two magnocellular (large cell) achromatic layers (M cells) and four parvocellular (small cell) chromatic layers (P cells). Within the LGN P-cell layers, there are two chromatic opponent types: red vs. green and blue vs. green/red.
5. After synapses at the LGN, the visual tract continues on back toward the primary visual cortex.