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Visual area V5, also known as visual area MT (middle temporal), is a region of extrastriate visual cortex that is thought to play a major role in the perception of motion, the integration of local motion signals into global percepts and the guidance of some eye movements [1].

Connections

MT is connected to a wide array of cortical and subcortical brain areas. Its inputs include the visual cortical areas V1, V2, and dorsal V3 (dorsomedial area),[2] [3] the koniocellular regions of the LGN [4], and the inferior pulvinar. 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 [5]

A standard view is that V1 provides the "most important" input to MT [1]. 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 (Rodman and collaborators 1989). Moreover, research by Semir Zeki and collaborators has suggested that certain types of visual information may reach MT before it reaches V1. This has been linked to the Riddoch phenomenon.

MT sends its major outputs to areas located in the cortex immediately surrounding it, including areas FST, 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 were tuned to the speed and direction of moving visual stimuli [6] [7]. These results suggested that MT played a significant role in the processing of visual motion.

Lesion studies have also supported the role of MT in visual perception and eye movements.

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. [8] For examples, lesion to the V5 lead 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, and then we use an electrode to stimulate it, the monkey becomes more likely to report 'upward' motion.[9]

There is still much controversy over the exact form of the computations carried out in area MT [10] and some research suggests that feature motion is in fact already available at lower levels of the visual system such as V1 [11] [12].

Functional Organization

MT was shown to be organized in direction columns [13]. DeAngelis argued that MT neurons were also organized based on their tuning for binocular disparity.[14]




See also

References & Bibliography

Key texts

Books

Papers

  1. 1.0 1.1 Born R, Bradley D. Structure and function of visual area MT.. Annu Rev Neurosci 28: 157-89. PMID 16022593.
  2. Felleman D, Van Essen D. Distributed hierarchical processing in the primate cerebral cortex.. Cereb Cortex 1 (1): 1-47. PMID 1822724.
  3. Ungerleider L, Desimone R (1986). Cortical connections of visual area MT in the macaque.. J Comp Neurol 248 (2): 190-222. PMID 3722458.
  4. Sincich L, Park K, Wohlgemuth M, Horton J (2004). Bypassing V1: a direct geniculate input to area MT.. Nat Neurosci 7 (10): 1123-8. PMID 15378066.
  5. Palmer SM, Rosa MG (2006). A distinct anatomical network of cortical areas for analysis of motion in far peripheral vision.. Eur J Neurosci 24(8): 2389-405.
  6. Dubner R, Zeki S (1971). Response properties and receptive fields of cells in an anatomically defined region of the superior temporal sulcus in the monkey.. Brain Res 35 (2): 528-32. PMID 5002708.
  7. Maunsell J, Van Essen D (1983). Functional properties of neurons in middle temporal visual area of the macaque monkey. I. Selectivity for stimulus direction, speed, and orientation.. J Neurophysiol 49 (5): 1127-47. PMID 6864242.
  8. 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.
  9. Britten & Van Wezel 1998
  10. Wilson, H.R., Ferrera, V.P., & Yo, C. (1992). A psychophysically motivated model for two-dimensional motion perception. Vis Neurosci, 9 (1), 79-97.
  11. Tinsley, C.J., Webb, B.S., Barraclough, N.E., Vincent, C.J., Parker, A., & Derrington, A.M. (2003). The nature of V1 neural responses to 2D moving patterns depends on receptive-field structure in the marmoset monkey. J Neurophysiol, 90 (2), 930-937.
  12. Pack & Born, 2003
  13. Albright T (1984). Direction and orientation selectivity of neurons in visual area MT of the macaque.. J Neurophysiol 52 (6): 1106-30. PMID 6520628.
  14. DeAngelis G, Newsome W (1999). Organization of disparity-selective neurons in macaque area MT.. J Neurosci 19 (4): 1398-415. PMID 9952417.

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Telencephalon (cerebrum, cerebral cortex, cerebral hemispheres) - edit

primary sulci/fissures: medial longitudinal, lateral, central, parietoöccipital, calcarine, cingulate

frontal lobe: precentral gyrus (primary motor cortex, 4), precentral sulcus, superior frontal gyrus (6, 8), middle frontal gyrus (46), inferior frontal gyrus (Broca's area, 44-pars opercularis, 45-pars triangularis), prefrontal cortex (orbitofrontal cortex, 9, 10, 11, 12, 47)

parietal lobe: postcentral sulcus, postcentral gyrus (1, 2, 3, 43), superior parietal lobule (5), inferior parietal lobule (39-angular gyrus, 40), precuneus (7), intraparietal sulcus

occipital lobe: primary visual cortex (17), cuneus, lingual gyrus, 18, 19 (18 and 19 span whole lobe)

temporal lobe: transverse temporal gyrus (41-42-primary auditory cortex), superior temporal gyrus (38, 22-Wernicke's area), middle temporal gyrus (21), inferior temporal gyrus (20), fusiform gyrus (36, 37)

limbic lobe/fornicate gyrus: cingulate cortex/cingulate gyrus, anterior cingulate (24, 32, 33), posterior cingulate (23, 31),
isthmus (26, 29, 30), parahippocampal gyrus (piriform cortex, 25, 27, 35), entorhinal cortex (28, 34)

subcortical/insular cortex: rhinencephalon, olfactory bulb, corpus callosum, lateral ventricles, septum pellucidum, ependyma, internal capsule, corona radiata, external capsule

hippocampal formation: dentate gyrus, hippocampus, subiculum

basal ganglia: striatum (caudate nucleus, putamen), lentiform nucleus (putamen, globus pallidus), claustrum, extreme capsule, amygdala, nucleus accumbens

Some categorizations are approximations, and some Brodmann areas span gyri.

Sensory system - Visual system - edit
Eye | Optic nerve | Optic chiasm | Optic tract | Lateral geniculate nucleus | Optic radiation | Visual cortex

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