Visual cortex: Difference between revisions

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The '''visual cortex''' of the [[brain]] is the area of the [[cerebral cortex]] that processes [[visual perception|visual information]]. It is located in the [[occipital lobe]]. Sensory input originating from the [[eye]]s travels through the [[lateral geniculate nucleus]] in the [[thalamus]] and then reaches the visual cortex. The area of the visual cortex that receives the sensory input from the lateral geniculate nucleus is the primary visual cortex, also known as visual area 1 ([[Brodmann area#BA17,V1|V1]]), [[Brodmann area]] 17<!---don't wikilink it as long as it redirects to here--->, or the '''striate cortex'''. The [[extrastriate cortex|extrastriate]] areas consist of visual areas 2, 3, 4, and 5 (also known as V2, V3, V4, and V5, or [[Brodmann area 18]] and all [[Brodmann area 19]]).<ref>{{cite web | vauthors = Mather G |title=The Visual Cortex |url=http://www.lifesci.sussex.ac.uk/home/George_Mather/Linked%20Pages/Physiol/Cortex.html |publisher=School of Life Sciences: University of Sussex |access-date=6 March 2017 |language=en |archive-date=2017-02-03 |archive-url=https://web.archive.org/web/20170203175847/http://www.lifesci.sussex.ac.uk/home/George_Mather/Linked%20Pages/Physiol/Cortex.html |url-status=dead }}</ref>

Both [[cerebral hemisphere|hemispheres of the brain]] include a visual cortex; the visual cortex in the left hemisphere receives signals from the right [[visual field]], and the visual cortex in the right hemisphere receives signals from the left visual field.

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The receptive fields of V1 neurons<ref>{{cite journal |vauthors=DeAngelis GC, Ohzawa I, Freeman RD |date=October 1995 |title=Receptive-field dynamics in the central visual pathways |journal=Trends in Neurosciences |volume=18 |issue=10 |pages=451–458 |doi=10.1016/0166-2236(95)94496-r |pmid=8545912 |s2cid=12827601}}</ref><ref>{{Cite book |title=The Visual Neurosciences, 2-vol. Set |vauthors=DeAngelis GC, Anzai A |date=2003-11-21 |publisher=The MIT Press |isbn=978-0-262-27012-0 |veditors=Chalupa LM, Werner JS |volume=1 |___location=Cambridge |pages=704–719 |language=en |chapter=A Modern View of the Classical Receptive Field: Linear and Nonlinear Spatiotemporal Processing by V1 Neurons |doi=10.7551/mitpress/7131.003.0052 |chapter-url=https://direct.mit.edu/books/book/5395/chapter/3948206/A-Modern-View-ofthe-Classical-Receptive-Field}}</ref> resemble Gabor functions, so the operation of the visual cortex has been compared to the [[Gabor transform]].{{Citation needed|date=May 2023}}

Later in time (after 100 ms), neurons in V1 are also sensitive to the more global organisation of the scene.<ref>{{Cite journal |last=Lamme |first=Victor A.F. |last2=Roelfsema |first2=Pieter R. |date=November 2000 |title=The distinct modes of vision offered by feedforward and recurrent processing |url=https://linkinghub.elsevier.com/retrieve/pii/S016622360001657X |journal=Trends in Neurosciences |volume=23 |issue=11 |pages=571–579 |doi=10.1016/s0166-2236(00)01657-x |issn=0166-2236|url-access=subscription }}</ref> These response properties probably stem from recurrent [[feedback]] processing (the influence of higher-tier cortical areas on lower-tier cortical areas) and lateral connections from [[Pyramidal cell|pyramidal neurons]].<ref name="Hupé_1998">{{cite journal | vauthors = Hupé JM, James AC, Payne BR, Lomber SG, Girard P, Bullier J | title = Cortical feedback improves discrimination between figure and background by V1, V2 and V3 neurons | journal = Nature | volume = 394 | issue = 6695 | pages = 784–7 | date = August 1998 | pmid = 9723617 | doi = 10.1038/29537 | bibcode = 1998Natur.394..784H }}</ref> While feedforward connections are mainly driving, feedback connections are mostly modulatory in their effects.<ref name="Angelucci_2003">{{cite journal | vauthors = Angelucci A, Bullier J | title = Reaching beyond the classical receptive field of V1 neurons: horizontal or feedback axons? | journal = Journal of Physiology, Paris | volume = 97 | issue = 2–3 | pages = 141–54 | date = 2003 | pmid = 14766139 | doi = 10.1016/j.jphysparis.2003.09.001 }}</ref><ref name="Bullier_2001">{{cite book | vauthors = Bullier J, Hupé JM, James AC, Girard P | title = The role of feedback connections in shaping the responses of visual cortical neurons | chapter = Chapter 13 the role of feedback connections in shaping the responses of visual cortical neurons | series = Progress in Brain Research | volume = 134 | pages = 193–204 | date = 2001 | pmid = 11702544 | doi = 10.1016/s0079-6123(01)34014-1 | isbn = 978-0-444-50586-6 }}</ref> Evidence shows that feedback originating in higher-level areas such as V4, IT, or MT, with bigger and more complex receptive fields, can modify and shape V1 responses, accounting for contextual or extra-classical receptive field effects.<ref name="Murray_2004">{{cite journal | vauthors = Murray SO, Schrater P, Kersten D | title = Perceptual grouping and the interactions between visual cortical areas | journal = Neural Networks | volume = 17 | issue = 5–6 | pages = 695–705 | date = 2004 | pmid = 15288893 | doi = 10.1016/j.neunet.2004.03.010 }}</ref><ref name="Huang_2007">{{cite journal | vauthors = Huang JY, Wang C, Dreher B | title = The effects of reversible inactivation of postero-temporal visual cortex on neuronal activities in cat's area 17 | journal = Brain Research | volume = 1138 | issue = | pages = 111–28 | date = March 2007 | pmid = 17276420 | doi = 10.1016/j.brainres.2006.12.081 }}</ref><ref name="Williams_2008">{{cite journal | vauthors = Williams MA, Baker CI, Op de Beeck HP, Shim WM, Dang S, Triantafyllou C, Kanwisher N | title = Feedback of visual object information to foveal retinotopic cortex | journal = Nature Neuroscience | volume = 11 | issue = 12 | pages = 1439–45 | date = December 2008 | pmid = 18978780 | pmc = 2789292 | doi = 10.1038/nn.2218 }}</ref>

The visual information relayed by V1 is sometimes described as [[edge detection]].<ref>{{cite journal | vauthors = Kesserwani H | title = The Biophysics of Visual Edge Detection: A Review of Basic Principles | journal = Cureus | volume = 12 | issue = 10 | pages = e11218 | date = October 2020 | pmid = 33269147 | pmc = 7706146 | doi = 10.7759/cureus.11218 | doi-access = free }}</ref> As an example, for an image comprising half side black and half side white, the dividing line between black and white has strongest local contrast (that is, edge detection) and is encoded, while few neurons code the brightness information (black or white per se). As information is further relayed to subsequent visual areas, it is coded as increasingly non-local frequency/phase signals. Note that, at these early stages of cortical visual processing, spatial ___location of visual information is well preserved amid the local contrast encoding (edge detection).

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'''Visual area V2''', or '''secondary visual cortex''', also called '''prestriate cortex''',<ref>{{cite book | vauthors = Gazzaniga MS, Ivry RB, Mangun GR | date = 2002 | title = Cognitive Neuroscience: The Biology of the Mind | edition = 2nd | publisher = W W Norton & Co Inc | isbn = 978-0-393-97777-6 }}</ref> receives strong feedforward connections from V1 (direct and via the pulvinar) and sends robust connections to V3, V4, and V5. Additionally, it plays a crucial role in the integration and processing of visual information.

The feedforward connections from V1 to V2 contribute to the hierarchical processing of visual stimuli. V2 neurons build upon the basic features detected in V1, extracting more complex visual attributes such as texture, depth, and color. This hierarchical processing is essential for the construction of a more nuanced and detailed representation of the visual scene.

Furthermore, the reciprocal feedback connections from V2 to V1 play a significant role in modulating the activity of V1 neurons. This feedback loop is thought to be involved in processes such as attention, perceptual grouping, and figure-ground segregation. The dynamic interplay between V1 and V2 highlights the intricate nature of information processing within the visual system.

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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>

== Middle temporal visual area (V5) <span class="anchor" id="V5"></span> ==<!-- This section isSection linked from the [[V5]] disambiguation page-->

The '''middle temporal visual area''' ('''MT''' or '''V5''') is a region of extrastriate visual cortex. In several species of both [[New World monkey]]s and [[Old World monkey]]s the MT area contains a high concentration of direction-selective neurons.<ref name="BornBradley" /> The MT in primates is thought to play a major role in the [[motion perception|perception of motion]], the integration of local motion signals into global percepts, and the guidance of some [[Eye movement (sensory)|eye movements]].<ref name="BornBradley">{{cite journal | vauthors = Born RT, Bradley DC | title = Structure and function of visual area MT | journal = Annual Review of Neuroscience | volume = 28 | pages = 157–189 | year = 2005 | pmid = 16022593 | doi = 10.1146/annurev.neuro.26.041002.131052 }}</ref>