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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/05/09 23:18:39」(JST)

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The optic radiation (also known as the geniculocalcarine tract, the geniculostriate pathway, and posterior thalamic radiation) are axons from the neurons in the lateral geniculate nucleus to the primary visual cortex. The optic radiation receives blood through deep branches of the middle cerebral artery and posterior cerebral artery.

They carry visual information through two divisions (called upper and lower division) to the visual cortex (also called striate cortex) along the calcarine fissure. There is one such tract on each side of the brain. If a lesion only exists in one optic radiation, the consequence is called quadrantanopia, which implies that only the respective superior or inferior quadrant of the visual field is affected.

Structure

The upper division:

Projects to the upper bank of the calcarine fissure, called the cuneus
Contains input from the superior retinal quadrants, which represents the inferior visual field quadrants
Transection causes contralateral lower quadrantanopia
Lesions that involve both cunei cause a lower altitudinal hemianopia (altitudinopia)

The lower division:

Loops from the lateral geniculate body anteriorly (Meyer's loop), then posteriorly, to terminate in the lower bank of the calcarine sulcus, called the lingual gyrus
Contains input from the inferior retinal quadrants, which represents the superior visual field quadrants
Transection causes contralateral upper quadrantanopia
Transection of both lingual gyri causes an upper altitudinal hemianopia

Parts

A distinctive feature of the optic radiations is that they split into two parts on each side:

Source	Path	Information	Damage
Fibers from the inferior retina (also called "Meyer's loop" or "Archambault's loop")	must pass through the temporal lobe by looping around the inferior horn of the lateral ventricle.	Carry information from the superior part of the visual field	A lesion in the temporal lobe that results in damage to Meyer's loop causes a characteristic loss of vision in a superior quadrant (quadrantanopia or "pie in the sky" defect.)
Fibers from the superior retina (also called "Baum's loop")	travel straight back through the parietal lobe to the occipital lobe in the retrolenticular limb of the internal capsule to the visual cortex.	Carry information from the inferior part of the visual field	Taking the shorter path, these fibers are less susceptible to damage. Damage caused is characteristically called "Pie in the floor" defect or inferior quadrantanopia.

Right superior quadrantanopia. The areas of the visual field lost in each eye are shown as black areas. This visual field defect is characteristic of damage to Meyer's loop on the left side of the brain.

Function

The optic radiation contains tracts which transmit visual information from the retina of the eye to the visual cortex. Lesions of the optic radiations are usually unilateral and commonly vascular in origin. Field defects therefore develop abruptly, in contrast to the slow progression of defects associated with tumors.

Clinical significance

Examination

Tracts contained within the optic radiation are examined as part of a cranial nerve examination.

Additional images

Horizontal section of right cerebral hemisphere.
Diagram of the tracts in the internal capsule.
3D schematic representation of optic tracts

External links

Kier LE, Staib LH, Davis, LM, Bronen, RA (1 May 2004). "MR Imaging of the Temporal Stem: Anatomic Dissection Tractography of the Uncinate Fasciculus, Inferior Occipitofrontal Fasciculus, and Meyer’s Loop of the Optic Radiation". Am J Neuroradiol 25 (5): 677–691. PMID 15140705. Retrieved 2007-12-19.
http://www2.umdnj.edu/~neuro/studyaid/Practical2000/Q34.htm
A 3D model of optic tract and optic radiation

UpToDate Contents

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English Journal

Visualization of nerve fiber orientation in gross histological sections of the human brain.

Axer H1, Berks G, Keyserlingk DG.
Microscopy research and technique.Microsc Res Tech.2000 Dec 1;51(5):481-92.
Diffusion weighted magnetic resonance imaging (DWMRI) allows visualization of the orientation of the nervous fibers in the living brain. For comparison, a method was developed to examine the orientation of fibers in histological sections of the human brain. Serial sections through the entire human b
PMID 11074619

[Hemianopsias in cortical and subcortical lesions of the visual system: what is the difference?].

Baumgartner G1.
Klinische Monatsblätter für Augenheilkunde.Klin Monbl Augenheilkd.1988 May;192(5):521-4.
The neuronal correlate of perception in the visual area remains unimpaired in lesions of the optic tracts or the radiatio optica. Hemianopsias due to lesions of these pathways are perceived immediately. On the contrary, hemianopsias due to a lesion of the visual cortex are not perceived or are only
PMID 3043100

Japanese Journal

パーキンソン症候群に対する前脈絡動脈血行遮断の治療効果機転に関する実験的研究第1編前脈絡動脈の分布領域について

岡山医学会雑誌 69(5), 1379-1389, 1957-05-31
NAID 120002753385

パーキンソン症候群に対する前脈絡動脈血行遮断の治療効果機転に関する実験的研究第2編前脈絡動脈血行遮断による組織学的変化について

岡山医学会雑誌 69(5), 1391-1404, 1957-05-31
NAID 120002753384

外膝状体及び其附近の組織像

Archivum histologicum japonicum 7(3), 327-341, 1954
NAID 130003881154

Related Pictures

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リンク元	「視放線」
関連記事	「optic」

「視放線」

Optic radiation
	Colour-coded diagram showing radiations in quadrants from retinal disc through the brain
Details
Identifiers
Latin	radiatio optica
NeuroNames	ancil-529
Dorlands; /Elsevier	r_01/12686139
TA	A14.1.08.673; A14.1.09.542; A14.1.09.547
FMA	61941
	Anatomical terms of neuroanatomy [edit on Wikidata]