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In terms of anatomy, V2 is split into four quadrants, a [[Dorsum (biology)|dorsal]] and [[ventral]] representation in the left and the right [[cerebral hemisphere|hemispheres]]. Together, these four regions provide a complete map of the visual world. V2 has many properties in common with V1: Cells are tuned to simple properties such as orientation, spatial frequency, and color. The responses of many V2 neurons are also modulated by more complex properties, such as the orientation of [[illusory contours]],<ref name="illusory contours">{{cite journal|last1=von der Heydt|first1=R|last2=Peterhans|first2=E|last3=Baumgartner|first3=G|title=Illusory contours and cortical neuron responses|journal=Science|date=1984|volume=224|issue=4654|pages=1260–62|doi=10.1126/science.6539501|pmid=6539501|bibcode=1984Sci...224.1260V}}</ref><ref name="A. Anzai, X. Peng 2007"/> [[binocular disparity]],<ref name="stereoscopic edges">{{cite journal|last1=von der Heydt|first1=R|last2=Zhou|first2=H|last3=Friedman|first3=H. S|title=Representation of stereoscopic edges in monkey visual cortex|journal=Vision Research|date=2000|volume=40|issue=15|pages=1955–67|doi=10.1016/s0042-6989(00)00044-4|pmid=10828464|s2cid=10269181|doi-access=free}}</ref> and whether the stimulus is part of the figure or the ground.<ref>{{cite journal|last1=Qiu|first1=F. T|last2=von der Heydt|first2=R|title=Figure and ground in the visual cortex: V2 combines stereoscopic cues with Gestalt rules|journal=Neuron|date=2005|volume=47|issue=1|pages=155–66|doi=10.1016/j.neuron.2005.05.028|pmid=15996555|pmc=1564069}}</ref><ref>{{cite journal|last1=Maruko, I; et alt.|title=Postnatal Development of Disparity Sensitivity in Visual Area 2 (V2) of Macaque Monkeys|journal=Journal of Neurophysiology|date=2008|volume=100|issue=5|pages=2486–2495|doi=10.1152/jn.90397.2008|pmid=18753321|pmc=2585398}}</ref> Recent research has shown that V2 cells show a small amount of attentional modulation (more than V1, less than V4), are tuned for moderately complex patterns, and may be driven by multiple orientations at different subregions within a single receptive field.
It is argued that the entire ventral visual-to-hippocampal stream is important for visual memory.<ref>{{cite journal|last1=Bussey|first1=T J|last2=Saksida|first2=L. M|author-link2=Lisa Saksida|date=2007|title=Memory, perception, and the ventral visual-perirhinal-hippocampal stream: thinking outside of the boxes|journal=Hippocampus|volume=17|issue=9|pages=898–908|doi=10.1002/hipo.20320|pmid=17636546|s2cid=13271331}}</ref> This theory, unlike the dominant one, predicts that object-recognition memory (ORM) alterations could result from the manipulation in V2, an area that is highly interconnected within the ventral stream of visual cortices. In the monkey brain, this area receives strong feedforward connections from the primary visual cortex (V1) and sends strong projections to other secondary visual cortices (V3, V4, and V5).<ref>{{cite journal|last1=Stepniewska|first1=I|last2=Kaas|first2=J. H.|title=Topographic patterns of V2 cortical connections in macaque monkeys|journal=The Journal of Comparative Neurology|date=1996|volume=371|issue=1|pages=129–152|doi=10.1002/(SICI)1096-9861(19960715)371:1<129::AID-CNE8>3.0.CO;2-5|pmid=8835723|s2cid=8500842}}</ref><ref>{{cite journal|last1=Gattas|first1=R|last2=Sousa|first2=A. P|last3=Mishkin|first3=M|last4=Ungerleider|first4=L. G.|title=Cortical projections of area V2 in the macaque|journal=Cerebral Cortex|date=1997|volume=7|issue=2|pages=110–129|doi=10.1093/cercor/7.2.110|pmid=9087820|doi-access=free}}</ref> Most of the neurons of this area in primates are tuned to simple visual characteristics such as orientation, spatial frequency, size, color, and shape.<ref name="A. Anzai, X. Peng 2007">{{cite journal|last1=Anzai|first1=A|last2=Peng|first2=X|last3=Van Essen|first3=D. C|title=Neurons in monkey visual area V2 encode combinations of orientations|journal=Nature Neuroscience|date=2007|volume=10|issue=10|pages=1313–21|pmid=17873872|doi=10.1038/nn1975|s2cid=6796448}}</ref><ref>{{cite journal|last1=Hegdé|first1=Jay|last2=Van Essen|first2=D. C|title=Selectivity for Complex Shapes in Primate Visual Area V2|journal=The Journal of Neuroscience|date=2000|volume=20|issue=5|pages=RC61|doi=10.1523/JNEUROSCI.20-05-j0001.2000|pmid=10684908|pmc=6772904|doi-access=free}}</ref><ref>{{cite journal|last1=Hegdé|first1=Jay|last2=Van Essen|first2=D. C|title=Temporal dynamics of shape analysis in Macaque visual area V2|journal= Journal of Neurophysiology|date=2004|volume=92|issue=5|pages=3030–3042|doi=10.1152/jn.00822.2003|pmid=15201315|s2cid=6428310
In one study, the Layer 6 cells of the V2 cortex were found to play a very important role in the storage of Object Recognition Memory as well as the conversion of short-term object memories into long-term memories.<ref>{{cite journal|last1=López-Aranda et alt.|title=Role of Layer 6 of V2 Visual Cortex in Object Recognition Memory|journal=Science|date=2009|volume=325|issue=5936|pages=87–89|doi=10.1126/science.1170869|pmid=19574389|bibcode=2009Sci...325...87L|s2cid=23990759}}</ref>
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The firing properties of V4 were first described by [[Semir Zeki]] in the late 1970s, who also named the area. Before that, V4 was known by its anatomical description, the [[prelunate gyrus]]. Originally, Zeki argued that the purpose of V4 was to process color information. Work in the early 1980s proved that V4 was as directly involved in form recognition as earlier cortical areas.{{citation needed|date=March 2016}} This research supported the [[two-streams hypothesis]], first presented by Ungerleider and Mishkin in 1982.
Recent work has shown that V4 exhibits long-term plasticity,<ref>{{cite journal|last1=Schmid|first1=M. C.|last2=Schmiedt|first2=J. T.|last3=Peters|first3=A. J.|last4=Saunders|first4=R. C.|last5=Maier|first5=A.|last6=Leopold|first6=D. A.|title=Motion-Sensitive Responses in Visual Area V4 in the Absence of Primary Visual Cortex|journal=Journal of Neuroscience|date=27 November 2013|volume=33|issue=48|pages=18740–18745|doi=10.1523/JNEUROSCI.3923-13.2013|pmid=24285880|pmc=3841445}}</ref> encodes stimulus salience, is gated by signals coming from the [[frontal eye fields]],<ref>{{Cite journal|last1=Moore|first1=Tirin|author-link1=Tirin Moore|last2=Armstrong|first2=Katherine M.|title=Selective gating of visual signals by microstimulation of frontal cortex|journal=Nature|volume=421|issue=6921|pages=370–373|doi=10.1038/nature01341|pmid=12540901|bibcode=2003Natur.421..370M|year=2003|s2cid=4405385}}</ref> and shows changes in the spatial profile of its receptive fields with attention.{{citation needed|date=March 2016}} In addition, it has recently been shown that activation of area V4 in humans (area V4h) is observed during the perception and retention of the color of objects, but not their shape.<ref>{{Citation |
== Middle temporal visual area (V5) ==<!-- This section is linked from [[V5]] -->
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=== Function ===
The first studies of the [[electrophysiological]] properties of neurons in MT showed that a large portion of the cells are [[neuronal tuning|tuned]] to the speed and direction of moving visual stimuli.<ref name="DubnerZeki">{{cite journal |vauthors=Dubner R, Zeki S | title = Response properties and receptive fields of cells in an anatomically defined region of the superior temporal sulcus in the monkey | journal = Brain Research | volume = 35 | issue = 2 | pages = 528–32 | year = 1971 | pmid = 5002708 | doi = 10.1016/0006-8993(71)90494-X}}.</ref><ref name="MaunsellVanEssen">{{cite journal |vauthors=Maunsell J, Van Essen D | title = Functional properties of neurons in middle temporal visual area of the macaque monkey. I. Selectivity for stimulus direction, speed, and orientation | journal = Journal of Neurophysiology | volume = 49 | issue = 5 | pages = 1127–47 | year = 1983 | pmid = 6864242| doi = 10.1152/jn.1983.49.5.1127 | s2cid = 8708245
[[Lesion]] studies have also supported the role of MT in motion perception and eye movements.<ref name=Dursteler1987>{{cite journal | title=Directional pursuit deficits following lesions of the foveal representation within the superior temporal sulcus of the macaque monkey |author1=Dursteler M.R. |author2=Wurtz R.H. |author3=Newsome W.T. | journal=Journal of Neurophysiology | year=1987 | volume=57 | issue=5 | pages=1262–87 | pmid=3585468|doi=10.1152/jn.1987.57.5.1262 |citeseerx=10.1.1.375.8659 }}</ref> [[Neuropsychology|Neuropsychological]] studies of a patient unable to see motion, seeing the world in a series of static 'frames' instead, suggested that V5 in the primate is homologous to MT in the human.<ref name=Hess1989>{{cite journal | title=The 'motion-blind' patient: low-level spatial and temporal filters |author1=Hess R.H. |author2=Baker C.L. |author3=Zihl J. | journal=Journal of Neuroscience | year=1989 | volume=9 | issue=5 | pages=1628–40 | pmid=2723744|pmc=6569833 |doi=10.1523/JNEUROSCI.09-05-01628.1989 }}</ref><ref name=Baker1991>{{cite journal | title=Residual motion perception in a 'motion-blind' patient, assessed with limited-lifetime random dot stimuli |author1=Baker C.L. Jr |author2=Hess R.F |author3=Zihl J. | journal=Journal of Neuroscience | year=1991 | volume=11 | issue=2 | pages=454–61 | pmid=1992012|pmc=6575225 |doi=10.1523/JNEUROSCI.11-02-00454.1991 }}</ref>
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===Properties===
Neurons in area DM/V6 of [[night monkey]]s and [[common marmoset]]s have unique response properties, including an extremely sharp selectivity for the orientation of visual contours, and preference for long, uninterrupted lines covering large parts of the visual field.<ref>{{cite journal |vauthors=Baker JF, etal | year = 1981 | title = Visual response properties of neurons in four extrastriate visual areas of the owl monkey (Aotus trivirgatus): a quantitative comparison of medial, dorsomedial, dorsolateral, and middle temporal areas
However, in comparison with area MT, a much smaller proportion of DM cells shows selectivity for the direction of motion of visual patterns.<ref name="fmritools.com">{{Cite web |url=http://www.fmritools.com/kdb/grey-matter/occipital-lobe/calcarine-visual-cortex/index.html |url-status=unfit |title=Calcarine (Visual) Cortex | Connectopedia Knowledge Database | Pr Denis Ducreux |access-date=2018-01-25 |archive-date=2018-01-20 |archive-url=https://web.archive.org/web/20180120053123/http://www.fmritools.com/kdb/grey-matter/occipital-lobe/calcarine-visual-cortex/index.html }}</ref> Another notable difference with area MT is that cells in DM are attuned to low spatial frequency components of an image, and respond poorly to the motion of textured patterns such as a field of random dots.<ref name="fmritools.com" /> These response properties suggest that DM and MT may work in parallel, with the former analyzing self-motion relative to the environment, and the latter analyzing the motion of individual objects relative to the background.<ref name="fmritools.com" />
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