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Optic chiasm
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For other meanings of "chiasm", see Chiasm.
Optic chiasma
Brain viewed from below; the front of the brain is above. Visual pathway with optic chiasm (X shape) is shown in red (1543 image from Andreas Vesalius' Fabrica)
Optic nerves, chiasm, and optic tracts
Details
Part of
Visual system
Identifiers
Latin
chiasma opticum
MeSH
A08.800.800.120.680.600
NeuroLex ID
Optic chiasm
TA
A14.1.08.403
FMA
62045
Anatomical terms of neuroanatomy
[edit on Wikidata]
The optic chiasm or optic chiasma ( /ɒptɪk kaɪæzəm/; Greek χίασμα, "crossing", from the Greek χιάζω 'to mark with an X', after the Greek letter 'Χ', chi) is the part of the brain where the optic nerves partially cross. The optic chiasm is located at the bottom of the brain immediately below the hypothalamus.[1] The optic chiasm is found in all vertebrates, although in cyclostomes (lampreys and hagfishes) it is located within the brain.[2][3]
Contents
[hide]
1 Structure
2 Other animals
3 Additional images
4 History
5 See also
6 References
7 External links
Structure[edit]
The optic nerve fibres on the nasal sides of each retina cross over (decussate) to the opposite side of the brain via the optic nerve at the optic chiasm (decussation of medial fibers). The temporal hemiretina, on the other hand, stays on the same side. The inferonasal retina are related to anterior portion of the optic chiasm whereas superonasal retinal fibers are related to the posterior portion of the optic chiasm.
The crossing over of optic nerve fibres at the optic chiasm allows the visual cortex to receive the same hemispheric visual field from both eyes. Superimposing and processing these monocular visual signals allow the visual cortex to generate binocular and stereoscopic vision. For example, the right visual cortex receives the temporal visual field from the left eye, and the nasal visual field from the right eye, which results in the right visual cortex producing a binocular image of the left hemispheric visual field. The net result of optic nerve crossing over at the optic chiasm is for the right cerebral hemisphere to sense and process left hemispheric vision, and for the left cerebral hemisphere to sense and process right hemispheric vision.[4]
This crossing is an adaptive feature of frontally oriented eyes, found mostly in predatory animals requiring precise visual depth perception. (Prey animals, with laterally positioned eyes, have little binocular vision, so there is a more complete crossover of visual signals[citation needed].) Beyond the optic chiasm, with crossed and uncrossed fibers, the optic nerves become optic tracts. The signals are passed on to the lateral geniculate body, in turn giving them to the occipital cortex (the outer matter of the rear brain).[5]
Other animals[edit]
In Siamese cats with certain genotypes of the albino gene, this wiring is disrupted, with more of the nerve-crossing than is normal, as a number of scholars have reported.[6] To compensate for lack of crossing in their brains, they cross their eyes (strabismus).[7]
This is also seen in albino tigers, as Guillery & Kaas report.[8]
Additional images[edit]
Scheme showing central connections of the optic nerves and optic tracts.
Base of brain.
3D schematic representation of optic tracts
Transformations of the visual field toward the visual map on the primary visual cortex.
Human brainstem anterior view
Optic chiasm
Optic chiasma
Cerebrum.Inferior view.Deep dissection.
Cerebrum.Inferior view. Deep dissection.
History[edit]
The crossing of nerve fibres, and the impact on vision that this had, was probably first identified by Persian physician "Esmail Jorjani", who appears to be Zayn al-Din Gorgani (1042–1137).[9]
See also[edit]
Wikimedia Commons has media related to Optic chiasm.
Chiasmal syndrome
References[edit]
Jump up ^ Colman, Andrew M. (2006). Oxford Dictionary of Psychology (2nd ed.). Oxford University Press. p. 530. ISBN 0-19-861035-1.
Jump up ^ Bainbridge, David (30 June 2009). Beyond the Zonules of Zinn: A Fantastic Journey Through Your Brain. Harvard University Press. p. 162. ISBN 978-0-674-02042-9. Retrieved 22 November 2015.
Jump up ^ de Lussanet, Marc H.E.; Osse, Jan W.M. (2012). "An ancestral axial twist explains the contralateral forebrain and the optic chiasm in vertebrates". Animal Biology. 62 (2): 193–216. arXiv:1003.1872  . doi:10.1163/157075611X617102. ISSN 1570-7555.
Jump up ^ Purves, Dale; Augustine, George; Fitzpatrick, David; Hall, William; LaMantia, Anthony-Samuel; White, Leonard (2012). Neuroscience. Sinauer Associates. p. 261. ISBN 978-0-87893-695-3.
Jump up ^ "eye, human." Encyclopædia Britannica from Encyclopædia Britannica 2006 Ultimate Reference Suite DVD 2009
Jump up ^ Schmolesky MT, Wang Y, Creel DJ, Leventhal AG. "Abnormal retinotopic organization of the dorsal lateral geniculate nucleus of the tyrosinase-negative albino cat". J Comp Neurol. 427 (2): 209–19. doi:10.1002/1096-9861(20001113)427:2<209::aid-cne4>3.0.co;2-3. PMID 11054689.
Jump up ^ Guillery, RW; Kaas, JH (June 1973). "Genetic abnormality of the visual pathways in a "white" tiger". Science. 180 (4092): 1287–9. Bibcode:1973Sci...180.1287G. doi:10.1126/science.180.4092.1287. PMID 4707916.
Jump up ^ Guillery RW (May 1974). "Visual pathways in albinos". Sci. Am. 230 (5): 44–54. doi:10.1038/scientificamerican0574-44. PMID 4822986.
Jump up ^ Davis, Matthew C.; Griessenauer, Christoph J.; Bosmia, Anand N.; Tubbs, R. Shane; Shoja, Mohammadali M. (2014-01-01). "The naming of the cranial nerves: A historical review". Clinical Anatomy. 27 (1): 14–19. doi:10.1002/ca.22345. ISSN 1098-2353.
Jeffery G (October 2001). "Architecture of the optic chiasm and the mechanisms that sculpt its development". Physiol. Rev. 81 (4): 1393–414. PMID 11581492.
External links[edit]
"Anatomy diagram: 13048.000-1". Roche Lexicon - illustrated navigator. Elsevier. Archived from the original on 2014-01-01.
[hide]
v
t
e
The cranial nerves
terminal
Nuclei
Septal nuclei
Course
no significant branches
olfactory
Nuclei
Anterior olfactory nucleus
Course
olfactory bulb
olfactory tract
optic
Nuclei
Lateral geniculate nucleus
Course
optic chiasm
optic tract
oculomotor
Nuclei
Oculomotor nucleus
Edinger–Westphal nucleus
Branches
superior
parasympathetic root of ciliary ganglion/ciliary ganglion
inferior
trochlear
Nucleus
Branches
no significant branches
trigeminal
Nuclei
PSN
Spinal trigeminal nucleus
MN
TMN
Course
trigeminal ganglion
Branches
ophthalmic
maxillary
mandibular
abducens
Nucleus
Branches
no significant branches
facial
near origin
intermediate nerve
geniculate
inside
facial canal
greater petrosal
pterygopalatine ganglion
nerve to the stapedius
chorda tympani
lingual nerve
submandibular ganglion
at stylomastoid
foramen
posterior auricular
suprahyoid
digastric
stylohyoid
parotid plexus
temporal
zygomatic
buccal
mandibular
cervical
Nuclei
Facial motor nucleus
Solitary nucleus
Superior salivary nucleus
vestibulocochlear
Nuclei
Vestibular nuclei
Cochlear nuclei
cochlear nerve
striae medullares
lateral lemniscus
vestibular
Scarpa's ganglion
glossopharyngeal
before jugular fossa
ganglia
superior
inferior
after jugular fossa
tympanic
tympanic plexus
lesser petrosal
otic ganglion
stylopharyngeal branch
pharyngeal branches
tonsillar branches
lingual branches
carotid sinus
Nuclei
Nucleus ambiguus
Inferior salivatory nucleus
Solitary nucleus
vagus
before jugular fossa
ganglia
superior
inferior
after jugular fossa
meningeal branch
auricular branch
neck
pharyngeal branch
pharyngeal plexus
superior laryngeal
external
internal
recurrent laryngeal (inferior)
superior cervical cardiac
thorax
inferior cardiac
pulmonary
vagal trunks
anterior
posterior
abdomen
celiac
renal
hepatic
anterior gastric
posterior gastric
Nuclei
Nucleus ambiguus
Dorsal nucleus of vagus nerve
Solitary nucleus
accessory
Nuclei
Nucleus ambiguus
Spinal accessory nucleus
cranial
spinal
hypoglossal
Nucleus
Branches
lingual
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