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The LGN receives information directly from the retina, and sends projections directly to the Primary visual cortex. In addition, it receives many strong feedback connections from the Primary visual cortex.
Ganglion cells of the retina send axons to the LGN through the optic nerve. Although it is generally considered to be a cranial nerve, and is always listed as cranial nerve II, in reality the retina and optic nerve arise as an outpocketing of the developing diencephalon. Rather than a proper nerve, then, the optic nerve is really a tract of the brain.The LGN is a distinctively layered structure ("geniculate" means "bent like a knee"). In most primates, including humans, it has six layers of cell bodies with layers of neuropil in between, in an arrangement something like a club sandwich or layer cake, with cell bodies of LGN neuronNeurons (also called nerve cells are the primary cells of the nervous system. In vertebrates, they are found in the brain, the spinal cord and in the nerves and ganglia of the peripheral nervous system. Classes There are three classes of neurons: afferents as the "cake" and neuropil as the " icingIcing (also frosting is a sweet glaze made of sugar, butter, water, and egg whites or milk, often flavoured and cooked and used to cover or decorate baked goods, such as cakes or cookies. Icing can be applied with a utensil such as a knife or frosting spa".
These six layers contain two types of cells. The cells in layers 1 and 2 are large, or magnocellular ; others in layers 3, 4, 5, and 6 are smaller, or parvocellular. (The LatinAlternative meanings: See Latin (disambiguation Latin was the language originally spoken in the region around Rome called Latium. It gained great importance as the formal language of the Roman Empire. All Romance languages are descended from Latin, and ma prefix "parvo-" means "small"; some authors prefer the term parvicellular. If you're searching for more information, try both spellings.)
Between each of the M and P layers lies a zone of very small cells: the interlaminar, or koniocellular (K), layers. K cells are functionally and neurochemically distinct from M and P cells and provide a thrid channel to visual cortex.
Magnocellular cells (commonly called M cells) have large cell bodies, use a relatively short time to process information, and are part of a visual processing system that tells the brain where something is. This system operates quickly but without much detail. They are found in layers 1 and 2 of the LGN, those layers more ventrally located which are next to the incoming optic tractThe optic tract is a part of the visual system in the brain. It is a continuation of the optic nerve and runs from the optic chiasm (where half of the information from each eye crosses sides, and half stays on the same side) to the lateral geniculate nucl fibers.
Parvocellular cells (commonly called P cells) have small cell bodies, use a relatively long time to process information, and are part of a visual processing system that tells the brain what something is. This system operates more slowly and with lots of information about details. For example, these cells carry colorColor vision is the visual ability to perceive and correctly interpret color (that is, different wavelengths of visible light) and especially lighting cues. In order for animals to respond accurately to their environments, their visual system need to corr information while magnocellular cells do not. Parvocellular cells are found in layers 3, 4, 5 and 6.