Editing Visual cortex (section)

== V4 ==
{{See also|Color center}}
[[File:Lingual gyrus animation.gif|thumb|The lingual gyrus is the hypothetical location of V4 in macaque monkeys. In humans, this area is called hV4.]]
[[File:Fusiform gyrus animation.gif|thumb|The fusiform gyrus is the hypothetical location of V4α, a secondary area for colour processing. More: [[Colour centre]]]]

'''Visual area V4''' is one of the visual areas in the [[extrastriate]] visual cortex. In [[Rhesus macaque|macaques]], it is located anterior to V2 and posterior to the [[Inferior temporal gyrus|posterior inferotemporal area (PIT)]]. It comprises at least four regions (left and right V4d, left and right V4v), and some groups report that it contains rostral and caudal subdivisions as well. It is unknown whether the human V4 is as expansive as that of the macaque [[homology (biology)|homologue]]. This is a subject of debate.<ref>{{cite journal | vauthors = Goddard E, Mannion DJ, McDonald JS, Solomon SG, Clifford CW | title = Color responsiveness argues against a dorsal component of human V4 | journal = Journal of Vision | volume = 11 | issue = 4 | page = 3 | date = April 2011 | pmid = 21467155 | doi = 10.1167/11.4.3 | doi-access = free }}</ref>

V4 is the third cortical area in the [[Two-streams hypothesis#Ventral stream|ventral stream]], receiving strong feedforward input from V2 and sending strong connections to the [[Inferior temporal gyrus|PIT]]. It also receives direct input from V1, especially for central space. In addition, it has weaker connections to V5 and the [[Angular gyrus|dorsal prelunate gyrus]] (DP).

V4 is the first area in the [[Two-streams hypothesis#Ventral stream|ventral stream]] to show strong attentional modulation. Most studies indicate that [[selective attention]] can change firing rates in V4 by about 20%. A seminal paper by Moran and Desimone characterizing these effects was the first paper to find attention effects anywhere in the visual cortex.<ref>{{cite journal | vauthors = Moran J, Desimone R | title = Selective attention gates visual processing in the extrastriate cortex | journal = Science | volume = 229 | issue = 4715 | pages = 782–784 | date = August 1985 | pmid = 4023713 | doi = 10.1126/science.4023713 | citeseerx = 10.1.1.308.6038 | bibcode = 1985Sci...229..782M }}</ref>

Like V2, V4 is tuned for orientation, spatial frequency, and color. Unlike V2, V4 is tuned for object features of intermediate complexity, like simple geometric shapes, although no one has developed a full parametric description of the tuning space for V4. Visual area V4 is not tuned for complex objects such as faces, as areas in the [[Inferior temporal gyrus|inferotemporal cortex]] are.

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 | vauthors = Schmid MC, Schmiedt JT, Peters AJ, Saunders RC, Maier A, Leopold DA | title = Motion-sensitive responses in visual area V4 in the absence of primary visual cortex | journal = The Journal of Neuroscience | volume = 33 | issue = 48 | pages = 18740–18745 | date = November 2013 | pmid = 24285880 | pmc = 3841445 | doi = 10.1523/JNEUROSCI.3923-13.2013 | doi-access = free }}</ref> encodes stimulus salience, is gated by signals coming from the [[frontal eye fields]],<ref>{{cite journal | vauthors = Moore T, Armstrong KM | title = Selective gating of visual signals by microstimulation of frontal cortex | journal = Nature | volume = 421 | issue = 6921 | pages = 370–373 | date = January 2003 | pmid = 12540901 | doi = 10.1038/nature01341 | s2cid = 4405385 | bibcode = 2003Natur.421..370M | author-link1 = Tirin Moore }}</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>{{cite conference | vauthors = Kozlovskiy S, Rogachev A |title=How Areas of Ventral Visual Stream Interact When We Memorize Color and Shape Information |date=2021 |book-title=Advances in Cognitive Research, Artificial Intelligence and Neuroinformatics. Intercognsci 2020 |series=Advances in Intelligent Systems and Computing |volume=1358 |pages=95–100 | veditors = Velichkovsky BM, Balaban PM, Ushakov VL |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-030-71637-0_10 |isbn=978-3-030-71636-3 }}</ref><ref>{{Cite journal | vauthors = Kozlovskiy S, Rogachev A |date=October 2021 |title=Ventral Visual Cortex Areas and Processing of Color and Shape in Visual Working Memory |journal=International Journal of Psychophysiology |language=en |volume=168 |issue=Supplement |pages=S155–S156 |doi=10.1016/j.ijpsycho.2021.07.437|s2cid=239648133 }}</ref>