Gray's FIG. 719– Hind- and mid-brains; postero-lateral view. (Lateral geniculate body visible near top.)

Gray's FIG. 722– Scheme showing central connections of the optic nerves and optic tracts. (Lateral geniculate body visible near center.)

Schematic diagram of the primate lateral geniculate nucleus.

The lateral geniculate nucleus (LGN) of the thalamus is a part of the brain, which is the primary processor of visual information, received from the retina, in the central nervous system. Image File history File links Gray719. ... Image File history File links Gray719. ... An illustration from the 1918 edition Henry Grays Anatomy of the Human Body, commonly known as Grays Anatomy, is an anatomy textbook widely regarded as a classic work on human anatomy. ... Image File history File links Gray722. ... Image File history File links Gray722. ... An illustration from the 1918 edition Henry Grays Anatomy of the Human Body, commonly known as Grays Anatomy, is an anatomy textbook widely regarded as a classic work on human anatomy. ... The optic nerve is the nerve that transmits visual information from the retina to the brain. ... Diagram of the lateral geniculate nucleus Diagram by User:jimhutchins. ... Diagram of the lateral geniculate nucleus Diagram by User:jimhutchins. ... Please wikify (format) this article as suggested in the Guide to layout and the Manual of Style. ... Comparative brain sizes In animals, the brain, or encephalon (Greek for in the head), is the control center of the central nervous system. ... Human eye cross-sectional view. ... A diagram showing the CNS: 1. ...

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. Brodmann area 17 (primary visual cortex) is shown in red in this image which also shows area 18 (orange) and 19 (yellow) The primary visual cortex (usually called V1) is the most well-studied visual area in the brain. ...

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. A ganglion cell (or sometimes called a gangliocyte) is a type of neuron located in the retina that receives visual information from photoreceptors via various intermediate cells such as bipolar cells, amacrine cells, and horizontal cells. ... An axon, or nerve fiber, is a long slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma. ... The optic nerve is the nerve that transmits visual information from the retina to the brain. ... Cranial nerves are nerves which start directly from the brainstem instead of the spinal cord. ... The diencephalon is the region of the brain that includes the epithalamus, thalamus, and hypothalamus. ... poop ...

Structure

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 neurons as the "cake" and neuropil as the "icing". Families 15, See classification A primate (L. prima, first) is any member of the biological order Primates, the group that contains all the species commonly related to the lemurs, monkeys, and apes, with the latter category including humans. ... Neuropil is the feltwork of unmyelinated neuronal processes (axonal and dendritic) within the gray matter of the central nervous system Traditionally, when pathologists looked at brain tissue they concentrated on neurons (the active functioning cells of the brain), glial cells and axons (especially in white matter, which is mostly composed... A club sandwich with fries photographed in Kimos, Liverpool, 6th August, 2005 // General A club sandwich, also called a clubhouse sandwich, is a type of sandwich. ... A birthday cake decorated with fruit, shaved chocolate, and candles. ... Drawing by Santiago Ramón y Cajal of cells in the pigeon cerebellum. ... Neuropil is the feltwork of unmyelinated neuronal processes (axonal and dendritic) within the gray matter of the central nervous system Traditionally, when pathologists looked at brain tissue they concentrated on neurons (the active functioning cells of the brain), glial cells and axons (especially in white matter, which is mostly composed... Icing (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. ...

These six layers contain two types of cells. The cells in layers 1 and 2 are large, or magnocellular (M); others in layers 3, 4, 5, and 6 are smaller, or parvocellular (P). (The Latin prefix "parvo-" means "small"; some authors prefer the term parvicellular. If you're searching for more information, try both spellings.) Latin is an ancient Indo-European language originally spoken in the region around Rome called Latium. ...

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 third channel to the visual cortex. Koniocellular refers to a visual pathway in the brains of some animals. ...

The magnocellular, parvocellular, and koniocellular layers of the LGN correspond with the similarly-named types of ganglion cells. A ganglion cell (or sometimes called a gangliocyte) is a type of neuron located in the retina that receives visual information from photoreceptors via various intermediate cells such as bipolar cells, amacrine cells, and horizontal cells. ...

M, P, K cells

Magnocellular cells have large cell bodies, use a relatively short time to process information. 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 tract fibers. Magnocellular parts, also called M cells, are cells in the brain concerned primarily with visual perception. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... The optic tract is a part of the visual system in the brain. ...

M Cells are the retinal ganglion cells that project their axons to the magnocellular layers of the LGN.

Parvocellular cells have small cell bodies, and use a relatively long time to process information. This system operates more slowly and with lots of information about details. For example, these cells carry color information while magnocellular cells do not. Parvocellular cells are found in layers 3, 4, 5 and 6. Parvocellular parts (also called P-cells), are slow-conducting neurons; transmitting information about colour vision, texture, pattern, and visual acuity. ... Color vision is the capacity of an organism or machine to distinguish objects based on the wavelength of the light they reflect or emit. ...

P Cells are the retinal ganglion cells that project their axons to the parvocellular layers of the LGN.

Koniocellular cells have very small cell bodies and are located in between the layers. The role of the koniocellular system in visual perception is presently unclear, however, it has been linked with integrating somatosensory-proprioceptive information with visual perception, and may also be involved in color perception. K Cells are the retinal ganglion cells that project their axons to the koniocellular layers of the LGN. Koniocellular refers to a visual pathway in the brains of some animals. ...

It should be noted that the parvo- and magnocellular fibers were previously thought to dominate the Ungerleider-Mishkin ventral and dorsal streams, respectively. However, new evidence has accumulated showing that the two streams appear to feed on a more even mixture of different types of nerve fibers. For a review, see Goodale & Milner, 1993, 1995.

The other major retino-cortical visual pathway is the retinotectal pathway, routing primarily through the superior colliculus and thalamic pulvinar nucleus onto posterior parietal and medial temporal cortices. Template:Biopsy

Ipsilateral and contralateral layers

In addition, the layers are divided up so that the eye on the same side (the ipsilateral eye) sends information to layers 2, 3 and 5, while the eye on the opposite side (the contralateral eye) sends information to layers 1, 4 and 6. (A simple mnemonic for this is that 2 + 3 = 5 while 1 + 4 does not equal 6, so it is "contra"ry to your knowledge of math.) A mnemonic (pronounced in American English, in British English) is a memory aid. ...

Remember that, in visual perception, the right eye gets information from the right side of the world (the right visual field), as well as the left side of the world (the left visual field). You can confirm this by covering your left eye: the right eye still sees to your left and right, although on the left side your field of view is partially blocked by your nose. Visual perception is one of the senses, consisting of the ability to detect light and interpret (see) it as the perception known as eyesight, sight or naked eye vision. ... The term visual field is sometimes used as a synonym to field of view, though they do not designate the same thing. ... The term visual field is sometimes used as a synonym to field of view, though they do not designate the same thing. ...

In the LGN, the corresponding information from the right and left eyes is "stacked" so that a toothpick driven through the club sandwich of layers 1 through 6 would hit the same point in visual space six different times. Wood toothpicks A toothpick is a piece of wood or other substance such as plastic used to remove food from the teeth after a meal. ... A club sandwich with fries photographed in Kimos, Liverpool, 6th August, 2005 // General A club sandwich, also called a clubhouse sandwich, is a type of sandwich. ...

LGN output

Information leaving the LGN travels out on the optic radiations, which form part of the retrolenticular limb of the internal capsule. The geniculo-calcerine tract (known as the optic radiation) is a collection of axons carrying visual information from the lateral geniculate nucleus of the thalamus to the primary visual cortex (also called striate cortex). ... The internal capsule is an area of white matter in the brain that separates the caudate nucleus and the thalamus from the lenticular nucleus. ...

The axons that leave the LGN go to V1 visual cortex. Both the magnocellular layers 1-2 and the parvocellular layers 3-6 send their axons to layer 4 in V1, with layer 4c feeding on parvo- and layer 4b on magnocellular input. However, the koniocellular layers (in between layers 1-6) send their axons to layers 2 and 3 in V1. An axon, or nerve fiber, is a long slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma. ... Visual cortex is the term applied to both the primary visual cortex (also known as striate cortex or V1) and upstream visual cortical areas also known as extrastriate cortical areas (V2, V3, V4, V5). ...

Axons from layer 6 of visual cortex send information back to the LGN. An axon, or nerve fiber, is a long slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma. ... Visual cortex is the term applied to both the primary visual cortex (also known as striate cortex or V1) and upstream visual cortical areas also known as extrastriate cortical areas (V2, V3, V4, V5). ...

Function in visual perception

The function of the LGN is unknown. It has been shown that the LGN introduces coding efficiencies by cancelling out redundant information from the retina, but there is almost certainly much more going on. Human eye cross-sectional view. ...

Like other areas of the thalamus, particularly other relay nuclei, the LGN likely helps the visual system focus its attention on the most important information. That is, if you hear a sound slightly to your left, the auditory system likely "tells" the visual system, through the LGN, to direct visual attention to that part of space. Please wikify (format) this article as suggested in the Guide to layout and the Manual of Style. ... The visual system is the part of the nervous system which allows organisms to see. ... The auditory system is the sensory system for the sense of hearing. ... The visual system is the part of the nervous system which allows organisms to see. ...

The LGN is also a station that refines certain receptive fields. Receptive fields are areas of the retina, producing a change in the firing of cells in the visual system. ...

Recent experiments using fMRI in humans have found that both spatial attention and saccadic eye movements can modulate activity in the LGN. Functional Magnetic Resonance Imaging (or fMRI) describes the use of MRI to measure hemodynamic signals related to neural activity in the brain or spinal cord of humans or other animals. ... A saccade is a fast movement of an eye, head, or other part of an animals body or of a device. ...

References

• Blohm G and Schreiber C. LGN in the visual pathway. Retrieved September 1, 2004.
• Harvey R. Really cool movie of a 3D reconstruction of monkey LGN. Retrieved September 1, 2004.
• Malpeli J. Malpeli Lab Home Page. Retrieved September 1, 2004.
• Nicholls J., et. al. From Neuron to Brain: Fourth Edition. Sinauer Associates, Inc. 2001.

External links

• Brain Atlas, Brain Maps, Neuroinformatics