Editing Blindsight (section)

== Cause ==
There are multiple theories about what causes blindsight. The first states that after damage to area V1, other branches of the [[optic nerve]] deliver visual information to the [[superior colliculus]], [[Pulvinar nuclei|pulvinar]]<ref>{{Cite journal|vauthors = Kinoshita M, Kato R, Isa K, Kobayashi K, Kobayashi K, Onoe H, Isa T|date=2019-01-11|title=Dissecting the circuit for blindsight to reveal the critical role of pulvinar and superior colliculus|journal=Nat Commun|volume=10|issue=1|page=135|language=en|doi=10.1038/s41467-018-08058-0|pmid=30635570|pmc=6329824|bibcode=2019NatCo..10..135K|s2cid=58009143}}</ref><ref>{{Cite journal|vauthors = Kletenik I, Ferguson MA, Bateman JR, Cohen AL, Lin C, Tetreault A, Pelak VS, Anderson CA, Prasad S, Darby RR, Fox MD|date=2021-12-27|title=Network Localization of Unconscious Visual Perception in Blindsight|journal=Ann Neurol|volume=91|issue=2|pages=217–224|language=en|doi=10.1002/ana.26292|pmid=34961965|s2cid=245553461|pmc=10013845}}</ref> and several other areas, including parts of the [[cerebral cortex]]. In turn, these areas might then control the blindsight responses.

Another explanation for the phenomenon of blindsight is that even though the majority of a person's visual cortex may be damaged, tiny islands of functioning tissue remain.<ref>{{Cite journal|vauthors = Radoeva PD, Prasad S, Brainard DH, Aguirre GK|date=2008-11-20|title=Neural activity within area V1 reflects unconscious visual performance in a case of blindsight|url=https://direct.mit.edu/jocn/article-abstract/20/11/1927/4595/Neural-Activity-within-Area-V1-Reflects?redirectedFrom=fulltext|journal=J Cogn Neurosci|volume=20|issue=11|pages=1927–1939|language=en|doi=10.1162/jocn.2008.20139|pmid=18416678|pmc=2773243}}</ref> These islands are not large enough to provide conscious perception, but nevertheless enough for some unconscious visual perception.<ref name=":0">{{cite book|title=Biological Psychology|vauthors = Kalat JW|date=2009|publisher=Wadsworth|isbn=9780495603009|edition=10th|location=Belmont, California|pages=169–170|oclc=236316740}}</ref>

A third theory is that the information required to determine the distance to and velocity of an object in object space is determined by the [[lateral geniculate nucleus]] (LGN) before the information is projected to the visual cortex. In a normal subject, these signals are used to merge the information from the eyes into a three-dimensional representation (which includes the position and velocity of individual objects relative to the organism), extract a [[vergence]] signal to benefit the precision (previously auxiliary) optical system, and extract a focus control signal for the [[Lens (anatomy)|lenses]] of the eyes. The [[Stereoscopic acuity|stereoscopic]] information is attached to the object information passed to the visual cortex.<ref>Fulton, J. (2004) Processes in Biological Vision Section 7.4 {{cite web|url=http://neuronresearch.net/vision/pdf/7Dynamics.pdf/|title=Archived copy|access-date=2012-11-26|url-status=dead|archive-url=https://web.archive.org/web/20150221000725/http://neuronresearch.net/vision/pdf/7Dynamics.pdf|archive-date=2015-02-21}}</ref>

More recently, with the demonstration of a direct input from the [[Lateral geniculate nucleus|LGN]] to area [[Visual cortex|V5]] (MT),<ref>{{cite journal|vauthors = Benevento LA, Yoshida K|title = The afferent and efferent organization of the lateral geniculo-prestriate pathways in the macaque monkey|journal = The Journal of Comparative Neurology|volume = 203|issue = 3|pages = 455–74|date = December 1981|pmid = 6274921|doi = 10.1002/cne.902030309|s2cid = 28585691}}</ref><ref>{{cite journal|vauthors = Fries W|title = The projection from the lateral geniculate nucleus to the prestriate cortex of the macaque monkey|journal = Proceedings of the Royal Society of London. Series B, Biological Sciences|volume = 213|issue = 1190|pages = 73–86|date = September 1981|pmid = 6117869|doi = 10.1098/rspb.1981.0054|bibcode = 1981RSPSB.213...73F|s2cid = 5700048}}</ref><ref>{{cite journal|vauthors = Yukie M, Iwai E|title = Direct projection from the dorsal lateral geniculate nucleus to the prestriate cortex in macaque monkeys|journal = The Journal of Comparative Neurology|volume = 201|issue = 1|pages = 81–97|date = September 1981|pmid = 7276252|doi = 10.1002/cne.902010107|s2cid = 8825689}}</ref><ref>{{cite journal|vauthors = Sincich LC, Park KF, Wohlgemuth MJ, Horton JC|title = Bypassing V1: a direct geniculate input to area MT|journal = Nature Neuroscience|volume = 7|issue = 10|pages = 1123–8|date = October 2004|pmid = 15378066|doi = 10.1038/nn1318|s2cid = 13419990}}</ref> which delivers signals from fast moving stimuli at latencies of about 30 ms,<ref>{{cite journal|vauthors = ffytche DH, Guy CN, Zeki S|title = The parallel visual motion inputs into areas V1 and V5 of human cerebral cortex|journal = Brain|volume = 118 ( Pt 6)|issue = 6|pages = 1375–94|date = December 1995|pmid = 8595471|doi = 10.1093/brain/118.6.1375}}</ref><ref>{{cite journal|vauthors = Beckers G, Zeki S|title = The consequences of inactivating areas V1 and V5 on visual motion perception|journal = Brain|volume = 118 ( Pt 1)|issue = 1|pages = 49–60|date = February 1995|pmid = 7895014|doi = 10.1093/brain/118.1.49}}</ref> another explanation has emerged. This one proposes that the delivery of these signals is sufficient to arouse a conscious experience of fast visual motion, without implying that it is V5 alone that is responsible, since once signals reach V5, they may be propagated to other areas of the brain.<ref name=":2" /><ref name="Schmid, M. Mrowka 2010"/><ref>{{cite journal|vauthors = Ffytche DH, Zeki S|title = The primary visual cortex, and feedback to it, are not necessary for conscious vision|journal = Brain|volume = 134|issue = Pt 1|pages = 247–57|date = January 2011|pmid = 21097490|pmc = 3159156|doi = 10.1093/brain/awq305}}</ref> The latter account would seem to exclude the possibility that signals are "pre-processed" by V1 or "post-processed" by it (through return connections from V5 back to V1), as has been suggested.<ref>{{Cite journal|last=Lamme|first=VAF|date=2001-04-01|title=Blindsight: the role of feedforward and feedback corticocortical connections|url=https://www.sciencedirect.com/science/article/abs/pii/S0001691801000208|journal=Acta Psychologica|language=en|volume=107|issue=1–3|pages=209–228|doi=10.1016/S0001-6918(01)00020-8|pmid=11388136|issn=0001-6918|access-date=2021-04-09|archive-date=2021-04-27|archive-url=https://web.archive.org/web/20210427175509/https://www.sciencedirect.com/science/article/abs/pii/S0001691801000208|url-status=live|url-access=subscription}}</ref> The pulvinar nucleus of the thalamus also sends direct, V1 by-passing, signals to V5<ref>{{Cite journal|date=1969-07-01|title=The topography of the afferent projections in the circumstriate visual cortex of the monkey studied by the nauta method|url=https://www.sciencedirect.com/science/article/abs/pii/004269896990011X|journal=Vision Research|language=en|volume=9|issue=7|pages=733–747|doi=10.1016/0042-6989(69)90011-X|issn=0042-6989|last1=Cragg|first1=B.G.|pmid=4979024|access-date=2021-04-09|archive-date=2022-08-13|archive-url=https://web.archive.org/web/20220813024247/https://www.sciencedirect.com/science/article/abs/pii/004269896990011X|url-status=live|url-access=subscription}}</ref> but their precise role in generating a conscious visual experience of motion has not yet been determined.

Evidence of blindsight can be indirectly observed in children as young as two months, although there is difficulty in determining the type in a patient who is not old enough to answer questions.<ref>{{cite journal|vauthors = Boyle NJ, Jones DH, Hamilton R, Spowart KM, Dutton GN|title = Blindsight in children: does it exist and can it be used to help the child? Observations on a case series|journal = Developmental Medicine and Child Neurology|volume = 47|issue = 10|pages = 699–702|date = October 2005|pmid = 16174315|doi = 10.1111/j.1469-8749.2005.tb01057.x|doi-access = free}}</ref>