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lateral geniculate nucleus
The lateral geniculate nucleus (LGN) (also called the lateral geniculate body or lateral geniculate complex) is a relay center in the thalamus for the visual pathway. It receives a major sensory input from the retina. The LGN is the main central connection for the optic nerve to the occipital lobe. Each LGN has six layers of neurons (grey matter) alternating with optic fibers (white matter).
It is small, ovoid, ventral projection at the termination of optic tract on each side of the brain. The LGN and the medial geniculate nucleus which deals with auditory information are both thalamic nuclei and so are present in both hemispheres.
The LGN receives information directly from the ascending retinal ganglion cells via the optic tract and from the reticular activating system. Neurons of the LGN send their axons through the optic radiation, a direct pathway to the primary visual cortex. In addition, the LGN receives many strong feedback connections from the primary visual cortex. In humans as well as other mammals, the two strongest pathways linking the eye to the brain are those projecting to the dorsal part of the LGN in the thalamus, and to the superior colliculus.〔Goodale, M. & Milner, D. (2004)''Sight unseen.''Oxford University Press, Inc.: New York.〕
==Structure==
Both the left and right hemisphere of the brain have a lateral geniculate nucleus, named after its resemblance to a bent knee (''genu'' is Latin for "knee"). In humans as well as in many other primates, it has layers of cell bodies that are interleaved with layers of koniocellular cells. In humans the LGN is normally described as having six distinctive layers. The inner two layers, (1 and 2) are called the magnocellular layers, while the outer four layers, (3,4,5 and 6), are called parvocellular layers. An additional set of neurons, known as the koniocellular layers, are found ventral to each of the magnocellular and parvocellular layers.〔Carlson, N. R. (2007)''Physiology of Behavior: ninth edition.''Pearson Education, Inc.: Boston.〕 This layering is variable between primate species, and extra leafleting is variable within species.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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