Editing Visual cortex (section)

== Middle temporal visual area (V5) ==<!-- This section is linked from [[V5]] -->
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>

=== Connections ===
MT is connected to a wide array of cortical and subcortical brain areas. Its input comes from visual cortical areas V1, V2 and dorsal V3 ([[dorsomedial area]]),<ref name="FellemanVanEssen">{{cite journal | vauthors = Felleman DJ, Van Essen DC | title = Distributed hierarchical processing in the primate cerebral cortex | journal = Cerebral Cortex | volume = 1 | issue = 1 | pages = 1–47 | year = 1991 | pmid = 1822724 | doi = 10.1093/cercor/1.1.1-a | doi-access = free }}</ref><ref name="UngerleiderDesimone">{{cite journal | vauthors = Ungerleider LG, Desimone R | title = Cortical connections of visual area MT in the macaque | journal = The Journal of Comparative Neurology | volume = 248 | issue = 2 | pages = 190–222 | date = June 1986 | pmid = 3722458 | doi = 10.1002/cne.902480204 | s2cid = 1876622 }}</ref> the [[koniocellular]] regions of the [[LGN]],<ref name="Sincich">{{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 = 1123–1128 | date = October 2004 | pmid = 15378066 | doi = 10.1038/nn1318 | s2cid = 13419990 }}</ref> and the [[pulvinar nuclei|inferior pulvinar]].<ref>{{cite journal | vauthors = Warner CE, Goldshmit Y, Bourne JA | title = Retinal afferents synapse with relay cells targeting the middle temporal area in the pulvinar and lateral geniculate nuclei | journal = Frontiers in Neuroanatomy | volume = 4 | pages = 8 | year = 2010 | pmid = 20179789 | pmc = 2826187 | doi = 10.3389/neuro.05.008.2010 | doi-access = free }}</ref> The pattern of projections to MT changes somewhat between the representations of the foveal and peripheral visual fields, with the latter receiving inputs from areas located in the midline cortex and [[retrosplenial region]].<ref name="PalmerRosa2006">{{cite journal | vauthors = Palmer SM, Rosa MG | title = A distinct anatomical network of cortical areas for analysis of motion in far peripheral vision | journal = The European Journal of Neuroscience | volume = 24 | issue = 8 | pages = 2389–2405 | date = October 2006 | pmid = 17042793 | doi = 10.1111/j.1460-9568.2006.05113.x | s2cid = 21562682 }}</ref>

A standard view is that V1 provides the "most important" input to MT.<ref name="BornBradley" /> Nonetheless, several studies have demonstrated that neurons in MT are capable of responding to visual information, often in a direction-selective manner, even after V1 has been destroyed or inactivated.<ref>{{cite journal | vauthors = Rodman HR, Gross CG, Albright TD | title = Afferent basis of visual response properties in area MT of the macaque. I. Effects of striate cortex removal | journal = The Journal of Neuroscience | volume = 9 | issue = 6 | pages = 2033–2050 | date = June 1989 | pmid = 2723765 | pmc = 6569731 | doi = 10.1523/JNEUROSCI.09-06-02033.1989 }}</ref> Moreover, research by [[Semir Zeki]] and collaborators has suggested that certain types of visual information may reach MT before it even reaches V1.

MT sends its major output to areas located in the cortex immediately surrounding it, including areas FST, [[Medial superior temporal area|MST]], and V4t (middle temporal crescent). Other projections of MT target the eye movement-related areas of the frontal and parietal lobes (frontal eye field and lateral intraparietal area).

=== 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 SM | 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 = 528–532 | date = December 1971 | pmid = 5002708 | doi = 10.1016/0006-8993(71)90494-X }}.</ref><ref name="MaunsellVanEssen">{{cite journal | vauthors = Maunsell JH, Van Essen DC | 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 = 1127–1147 | date = May 1983 | pmid = 6864242 | doi = 10.1152/jn.1983.49.5.1127 | s2cid = 8708245 }}</ref>

[[Lesion]] studies have also supported the role of MT in motion perception and eye movements.<ref name=Dursteler1987>{{cite journal | vauthors = Dürsteler MR, Wurtz RH, Newsome WT | title = Directional pursuit deficits following lesions of the foveal representation within the superior temporal sulcus of the macaque monkey | journal = Journal of Neurophysiology | volume = 57 | issue = 5 | pages = 1262–1287 | date = May 1987 | 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 | vauthors = Hess RH, Baker CL, Zihl J | title = The "motion-blind" patient: low-level spatial and temporal filters | journal = The Journal of Neuroscience | volume = 9 | issue = 5 | pages = 1628–1640 | date = May 1989 | pmid = 2723744 | pmc = 6569833 | doi = 10.1523/JNEUROSCI.09-05-01628.1989 }}</ref><ref name=Baker1991>{{cite journal | vauthors = Baker CL, Hess RF, Zihl J | title = Residual motion perception in a "motion-blind" patient, assessed with limited-lifetime random dot stimuli | journal = The Journal of Neuroscience | volume = 11 | issue = 2 | pages = 454–461 | date = February 1991 | pmid = 1992012 | pmc = 6575225 | doi = 10.1523/JNEUROSCI.11-02-00454.1991 }}</ref>

However, since neurons in V1 are also tuned to the direction and speed of motion, these early results left open the question of precisely what MT could do that V1 could not. Much work has been carried out on this region, as it appears to integrate local visual motion signals into the global motion of complex objects.<ref name="Movshon">Movshon, J.A., Adelson, E.H., Gizzi, M.S., & Newsome, W.T. (1985). The analysis of moving visual patterns. In: C. Chagas, R. Gattass, & C. Gross (Eds.), Pattern recognition mechanisms (pp. 117–151), Rome: Vatican Press.</ref>
For example, ''lesion'' to the V5 leads to deficits in perceiving motion and processing of complex stimuli. It contains many neurons selective for the motion of complex visual features (line ends, corners). ''Microstimulation'' of a neuron located in the V5 affects the perception of motion. For example, if one finds a neuron with preference for upward motion in a monkey's V5 and stimulates it with an electrode, then the monkey becomes more likely to report 'upward' motion when presented with stimuli containing 'left' and 'right' as well as 'upward' components.<ref name="BrittenVanWezel">{{cite journal | vauthors = Britten KH, van Wezel RJ | title = Electrical microstimulation of cortical area MST biases heading perception in monkeys | journal = Nature Neuroscience | volume = 1 | issue = 1 | pages = 59–63 | date = May 1998 | pmid = 10195110 | doi = 10.1038/259 | s2cid = 52820462 }}</ref>

There is still much controversy over the exact form of the computations carried out in area MT<ref name="Wilson">{{cite journal | vauthors = Wilson HR, Ferrera VP, Yo C | title = A psychophysically motivated model for two-dimensional motion perception | journal = Visual Neuroscience | volume = 9 | issue = 1 | pages = 79–97 | date = July 1992 | pmid = 1633129 | doi = 10.1017/s0952523800006386 | s2cid = 45196189 }}</ref> and some research suggests that feature motion is in fact already available at lower levels of the visual system such as V1.<ref name="Tinsley">{{cite journal | vauthors = Tinsley CJ, Webb BS, Barraclough NE, Vincent CJ, Parker A, Derrington AM | title = The nature of V1 neural responses to 2D moving patterns depends on receptive-field structure in the marmoset monkey | journal = Journal of Neurophysiology | volume = 90 | issue = 2 | pages = 930–937 | date = August 2003 | pmid = 12711710 | doi = 10.1152/jn.00708.2002 | s2cid = 540146 }}</ref><ref name="PackBorn">{{cite journal | vauthors = Pack CC, Born RT, Livingstone MS | title = Two-dimensional substructure of stereo and motion interactions in macaque visual cortex | journal = Neuron | volume = 37 | issue = 3 | pages = 525–535 | date = February 2003 | pmid = 12575958 | doi = 10.1016/s0896-6273(02)01187-x | doi-access = free }}</ref>

=== Functional organization ===
MT was shown to be organized in direction columns.<ref name="Albright">{{cite journal | vauthors = Albright TD | title = Direction and orientation selectivity of neurons in visual area MT of the macaque | journal = Journal of Neurophysiology | volume = 52 | issue = 6 | pages = 1106–1130 | date = December 1984 | pmid = 6520628 | doi = 10.1152/jn.1984.52.6.1106 }}</ref> DeAngelis argued that MT neurons were also organized based on their tuning for binocular disparity.<ref name="DeAngelisNewsome">{{cite journal | vauthors = DeAngelis GC, Newsome WT | title = Organization of disparity-selective neurons in macaque area MT | journal = The Journal of Neuroscience | volume = 19 | issue = 4 | pages = 1398–1415 | date = February 1999 | pmid = 9952417 | pmc = 6786027 | doi = 10.1523/JNEUROSCI.19-04-01398.1999 }}</ref>