Visual cortex

Cerebro: Visual cortex Brodmann area 17 (corteza visual primaria) is shown in red in this image which also shows area 18 (naranja) y 19 (amarillo) [[Imagen:|250Px|centro|]] Sujeto latino de Gray # Part of Components Artery Vein BrainInfo/UW - Malla [1] The visual cortex refers to the primary visual cortex (also known as striate cortex or V1) and extrastriate visual cortical areas such as V2, V3, V4, y V5. The primary visual cortex is anatomically equivalent to Brodmann area 17, or BA17. Brodmann areas are based on a histological map of the human brain created by Korbinian Brodmann. It is known as the striate cortex because it contains a layer of cells that show up as dark stripes under appropriate staining[1]. Contenido 1 Introducción 2 corteza visual primaria (V1) 2.1 Función 2.2 Current research 3 V2 4 V3 5 V4 6 V5/MT 6.1 Conexiones 6.2 Función 6.3 Organizacion funcional 7 Ver también 8 Referencias 9 External links Introduction The primary visual cortex, V1, is the koniocortex (sensory type) located in and around the calcarine fissure in the occipital lobe. It is the one that receives information directly from the lateral geniculate nucleus.To this have been added later as many as thirty interconnected (secondary or tertiary) visual areas. At the present time there is fair agreement for only 2 of these areas, V2 and MT (aka V5). While there is also good agreement about the existence and general layout of the third visual area (V3), there is still some controversy about its exact extent, in particular relative to the dorsomedial area (MD, or V6). la corriente dorsal (verde) y corriente ventral (violeta) son exhibidos. Se originan en la corteza visual primaria.. The first cortical visual area transmits information to two primary pathways, called the dorsal stream and the ventral stream: The dorsal stream begins with V1, goes through Visual area V2, then to the dorsomedial area and Visual area MT (also known as V5) and to the inferior parietal lobule. la corriente dorsal, sometimes called the "Where Pathway", is associated with motion, representation of object locations, and control of the eyes and arms, especially when visual information is used to guide saccades or reaching. [2] The ventral stream begins with V1, goes through Visual area V2, then through Visual area V4, and to the inferior temporal cortex. The ventral stream, sometimes called the "What Pathway", is associated with form recognition and object representation. It is also associated with storage of long-term memory. The dichotomy of the dorsal/ventral pathways (also called the "what/where" o "action/perception" streams) [2] was first defined by Ungerleider and Mishkin [3] and is still contentious among vision scientists and psychologists. It is probably an over-simplification of the true state of affairs in the visual cortex. It is based on the findings that visual illusions such as the Ebbinghaus illusion may distort judgements of a perceptual nature, but when the subject responds with an action, such as grasping, no distortion occurs. Sin embargo, recent work [4] suggests that both the action and perception systems are equally fooled by such illusions. Neurons in the visual cortex fire action potentials when visual stimuli appear within their receptive field. Por definición, the receptive field is the region within the entire visual field which elicits an action potential. But for any given neuron, it may respond to a subset of stimuli within its receptive field. This property is called tuning. In the earlier visual areas, neurons have simpler tuning. Por ejemplo, a neuron in V1 may fire to any vertical stimulus in its receptive field. In the higher visual areas, neurons have complex tuning. Por ejemplo, in the inferior temporal cortex (IT), a neuron may only fire when a certain face appears in its receptive field. The visual cortex receives its blood supply primarily from the calcarine branch of the posterior cerebral artery. corteza visual primaria (V1) The primary visual cortex is the best studied visual area in the brain. Like that of all mammals studied, it is located in the posterior pole of the occipital cortex (the occipital cortex is responsible for processing visual stimuli). It is the simplest, earliest cortical visual area. It is highly specialized for processing information about static and moving objects and is excellent in pattern recognition. The functionally defined primary visual cortex is approximately equivalent to the anatomically defined striate cortex. El nombre "striate cortex" is derived from the stria of Gennari, a distinctive stripe visible to the naked eye that represents myelinated axons from the lateral geniculate body terminating in layer 4 of the gray matter. The primary visual cortex is divided into six functionally distinct layers, labelled 1 a través de 6. Layer 4, which receives most visual input from the lateral geniculate nucleus (LGN), is further divided into 4 capas, labelled 4A, 4B, 4, and 4Cβ. Sublamina 4Cα receives most magnocellular input from the LGN, while layer 4Cβ receives input from parvocellular pathways. Function V1 has a very well-defined map of the spatial information in vision. Por ejemplo, in humans the upper bank of the calcarine sulcus responds strongly to the lower half of visual field (below the center), and the lower bank of the calcarine to the upper half of visual field. Conceptually, this retinotopy mapping is a transformation of the visual image from retina to V1. The correspondence between a given location in V1 and in the subjective visual field is very precise: even the blind spots are mapped into V1. Evolutionarily, this correspondence is very basic and found in most animals that possess a V1. In human and animals with a fovea in the retina, a large portion of V1 is mapped to the small, central portion of visual field, a phenomenon known as cortical magnification. Perhaps for the purpose of accurate spatial encoding, neurons in V1 have the smallest receptive field size of any visual cortex regions. The tuning properties of V1 neurons (what the neurons respond to) differ greatly over time. Early in time (40 ms and further) individual V1 neurons have strong tuning to a small set of stimuli. Es decir, the neuronal responses can discriminate small changes in visual orientations, spatial frequencies and colors. Además, individual V1 neurons in human and animals with binocular vision have ocular dominance, namely tuning to one of the two eyes. In V1, and primary sensory cortex in general, neurons with similar tuning properties tend to cluster together as cortical columns. David Hubel and Torsten Wiesel proposed the classic ice-cube organization model of cortical columns for two tuning properties: ocular dominance and orientation. Sin embargo, this model cannot accommodate the color, spatial frequency and many other features to which neurons are tuned. The exact organization of all these cortical columns within V1 remains a hot topic of current research. Current consensus seems to be that early responses of V1 neurons consists of tiled sets of selective spatiotemporal filters. In the spatial domain, the functioning of V1 can be thought of as similar to many spatially local, complex Fourier transforms. teóricamente, these filters together can carry out neuronal processing of spatial frequency, orientation, motion, dirección, velocidad (thus temporal frequency), and many other spatiotemporal features. Experiments of V1 neurons substantiate these theories, but also raise new questions. Later in time (después 100 ms) neurons in V1 are also sensitive to the more global organisation of the scene (Lamme & Roelfsema, 2000). These response properties probably stem from recurrent processing (the influence of higher-tier cortical areas on lower-tier cortical areas) and lateral connections from pyramidal neurons (Hupe et al 1998). The visual information relayed to V1 is not coded in terms of spatial (or optical) imagery, but rather as the local contrast. A modo de ejemplo, for an image comprising half side black and half side white, the divide line between black and white has strongest local contrast 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. Importantly, at these early stages of cortical visual processing, spatial location of visual information is well preserved amid the local contrast encoding. Current research Research on the primary visual cortex can involve recording action potentials from electrodes within the brain of cats, ferrets, mice, or monkeys, or through recording intrinsic optical signals from animals or fMRI signals from human and monkey V1. One recent discovery concerning the human V1 is that signals measured by fMRI show very large attentional modulation. This result strongly contrasts with macaque physiology research showing very small changes (or no changes) in firing associated with attentional modulation. Research with the macaque monkey is usually performed by measuring spiking activity from single neurons. The neural basis of the fMRI signal on the other hand is mostly related to post synaptic potentiation (PSP). This difference therefore does not necessarily indicate a difference between macaque and human physiology. Other current work on V1 seeks to fully characterize its tuning properties, and to use it as a model area for the canonical cortical circuit. Lesions to primary visual cortex usually lead to a scotoma, or hole in the visual field. Curiosamente, patients with scotomas are often able to make use of visual information presented to their scotomas, despite being unable to consciously perceive it. Este fenómeno, called blindsight, is widely studied by scientists interested in the neural correlate of consciousness. V2 Visual area V2 is the second major area in the visual cortex, y primera región dentro del área de asociación visual. It receives strong feedforward connections from V1 and sends strong connections to V3, V4, y V5. It also sends strong feedback connections to V1. Anatómicamente, V2 se divide en cuatro cuadrantes, una representación dorsal y ventral en los hemisferios izquierdo y derecho. Juntas, estas cuatro regiones proporcionan un mapa completo del mundo visual.. funcionalmente, V2 has many properties in common with V1. Las celdas se ajustan a propiedades simples como la orientación., frecuencia espacial, y color. Las respuestas de muchas neuronas V2 también están moduladas por propiedades más complejas., como la orientación de los contornos ilusorios y si el estímulo es parte de la figura o del fondo (Qiu y von der Heydt, 2005). Investigaciones recientes han demostrado que las células V2 muestran una pequeña cantidad de modulación atencional (más que V1, menos de V4), están ajustados para patrones moderadamente complejos, y puede ser impulsado por múltiples orientaciones en diferentes subregiones dentro de un solo campo receptivo. V3 Visual area V3 is a term used to refer to the region of cortex located immediately in front of V2. Hasta la fecha, existe cierta controversia con respecto a la extensión exacta de esta área, con algunos investigadores proponiendo que esto es de hecho un complejo de dos o tres subdivisiones funcionales. Por ejemplo, David Van Essen y otros (1986) han propuesto que la existencia de un "dorso V3" en la parte superior del hemisferio cerebral, que es distinto del "ventral V3" (o área posterior ventral, Vicepresidente) ubicado en la parte inferior del cerebro. Dorsal y ventral V3 tienen conexiones distintas con otras partes del cerebro, aparecen diferentes en las secciones teñidas con una variedad de métodos, y contienen neuronas que responden a diferentes combinaciones de estímulos visuales (por ejemplo, Las neuronas selectivas de color son más comunes en el V3 ventral.). Dorsal V3 normalmente se considera parte de la corriente dorsal, recibe entradas de V2 y del área visual primaria y se proyecta a la corteza parietal posterior. Puede estar ubicado anatómicamente en el área de Brodmann 19. Existe debate sobre si también hay áreas adyacentes 3A y 3B. El trabajo reciente con fMRI ha sugerido que el área V3/V3A puede desempeñar un papel en el procesamiento del movimiento global [5] Otros estudios prefieren considerar dorsal V3 como parte de un área más grande, nombró el área dorsomedial (MD), que contiene una representación de todo el campo visual. Las neuronas en el área DM responden al movimiento coherente de patrones grandes que cubren porciones extensas del campo visual (Luis y colaboradores, 2006). Ventral V3 (Vicepresidente), tiene conexiones mucho más débiles desde el área visual primaria, y conexiones más fuertes con la corteza temporal inferior. Si bien estudios anteriores propusieron que VP solo contenía una representación de la parte superior del campo visual (por encima del punto de fijación), un trabajo más reciente indica que esta área es más extensa de lo que se había apreciado anteriormente, y al igual que otras áreas visuales, puede contener una representación visual completa. El revisado, La VP más extensa se denomina área posterior ventrolateral. (VLP) by Rosa and Tweedale.[6] V4 Visual area V4 is one of the visual areas in the extrastriate visual cortex of the macaque monkey. It is located anterior to V2 and posterior to visual 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 what the human homologue of V4 is, and this issue is currently the subject of much scrutiny. V4 is the third cortical area in the ventral stream, receiving strong feedforward input from V2 and sending strong connections to the posterior inferotemporal cortex (PIT). It also receives direct inputs from V1, especially for central space. Además, it has weaker connections to V5 and visual area DP (the dorsal prelunate gyrus). V4 is the first area in the 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 [2]. [7] Like V1, V4 is tuned for orientation, frecuencia espacial, y color. Unlike V1, it 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 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. Originalmente, 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. 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, encodes stimulus salience, is gated by signals coming from the frontal eye fields, shows changes in the spatial profile of its receptive fields with attention, and encodes hazard functions. V5/MT Visual area V5, también conocida como área visual MT (medio temporal), es una región de la corteza visual extraestriada que se cree que juega un papel importante en la percepción del movimiento, la integración de señales de movimiento locales en percepciones globales y la guía de algunos movimientos oculares [8]. Connections MT is connected to a wide array of cortical and subcortical brain areas. Sus entradas incluyen las áreas corticales visuales V1, V2, y dorsal V3 (área dorsomedial),[9] [10] las regiones koniocelulares del LGN [11], y el pulvinar inferior. El patrón de proyecciones a MT cambia algo entre las representaciones de los campos visuales foveales y periféricos., con este último recibiendo información de áreas ubicadas en la línea media de la corteza y la región retroesplenial [12] Una vista estándar es que V1 proporciona la "lo más importante" entrada a MT [8]. No obstante, varios estudios han demostrado que las neuronas en MT son capaces de responder a la información visual, a menudo de manera selectiva en la dirección, even after V1 has been destroyed or inactivated.[13] Además, research by Semir Zeki and collaborators has suggested that certain types of visual information may reach MT before it even reaches V1. MT envía sus principales salidas a áreas ubicadas en la corteza que lo rodea inmediatamente, incluyendo áreas FST, MST y V4t (media luna temporal media). Otras proyecciones de MT se dirigen a las áreas relacionadas con el movimiento ocular de los lóbulos frontal y parietal. (campo ocular frontal y área intraparietal lateral). 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 [14] [15]. Estos resultados sugirieron que MT jugó un papel importante en el procesamiento del movimiento visual. Los estudios de lesiones también han respaldado el papel de la MT en la percepción visual y los movimientos oculares.. Sin embargo, ya que las neuronas en V1 también están sintonizadas con la dirección y la velocidad del movimiento, estos primeros resultados dejaron abierta la cuestión de qué podía hacer precisamente MT que V1 no podía. Se ha trabajado mucho en esta región, ya que parece integrar señales de movimiento visual local en el movimiento global de objetos complejos.. [16] Por ejemplo, La lesión de V5 conduce a deficiencias en la percepción del movimiento y el procesamiento de estímulos complejos.. Contiene muchas neuronas selectivas para el movimiento de características visuales complejas. (extremos de línea, esquinas). La microestimulación de una neurona ubicada en el V5 afecta la percepción del movimiento. Por ejemplo, si uno encuentra una neurona con preferencia por el movimiento hacia arriba, y luego usamos un electrodo para estimularlo, el mono se vuelve más propenso a informar de un movimiento "hacia arriba".[17] Todavía hay mucha controversia sobre la forma exacta de los cálculos realizados en el área MT [18] y algunas investigaciones sugieren que el movimiento de funciones ya está disponible en niveles más bajos del sistema visual, como V1 [19] [20]. Functional Organization MT was shown to be organized in direction columns [21]. DeAngelis argumentó que las neuronas MT también se organizaron en función de su sintonía para la disparidad binocular.[22] See also Brodmann area Cortical area Cortical blindness Feature integration theory List of regions in the human brain Retinotopy Vision Visual receptive fields Visual perception References ↑ Reber, A.S. & Reber, E.S. (2001). Dictionary of psychology. Londres:Penguin ↑ Jump up to: 2.0 2.1 Goodale & Milner (1992). Separate pathways for perception and action.. Trends in Neuroscience 15: 20-25. ↑ Ungerleider and Mishkin (1982). Ingle DJ, Goodale MA and Mansfield RJW Analysis of Visual Behavior, Prensa del MIT. ↑ Franz VH, Scharnowski F, Gegenfurtner (2005). Illusion effects on grasping are temporally constant not dynamic.. J Exp Psychol Hum Percept Perform. 31(6): 1359-78. ↑ Braddick, DO, O'Brian, JMD, et al (2001). Áreas del cerebro sensibles al movimiento visual.. Percepción 30: 61-72. ↑ Rosa MG, Tweedale R (2000) Visual areas in lateral and ventral extrastriate cortices of the marmoset monkey. J Comp Neurol 422:621-51. ↑ Moran & Desimone. Selective Attention Gates Visual Processing in the Extrastriate Cortex. Ciencia 229(4715), 1985. ↑ Saltar hasta: 8.0 8.1 Nacido R, bradley d. Estructura y función del área visual MT.. Annu Rev Neurosci 28: 157-89. PMID 16022593. Error de cita: No válido etiqueta; nombre "NacidoBradley" definido varias veces con diferente contenido ↑ Felleman D, van essen d. Procesamiento jerárquico distribuido en la corteza cerebral de los primates.. corteza cerebral 1 (1): 1-47. PMID 1822724. ↑ Ungerleider L., Desimone R (1986). Conexiones corticales del área visual MT en el macaco.. J Comp Neurol 248 (2): 190-222. PMID 3722458. ↑ Sincich L., parque k, Wohlgemuth M, Horton J. (2004). Omitir V1: una entrada geniculada directa al área MT.. Nat neurosci 7 (10): 1123-8. PMID 15378066. ↑ PalmerSM, escuadrón ametralladora (2006). Una red anatómica distinta de áreas corticales para el análisis del movimiento en la visión periférica lejana.. Eur J Neurosci 24(8): 2389-405. ↑ Rodman HR, Gross CG, Albright TD (1989) Afferent basis of visual response properties in area MT of the macaque. Yo. Effects of striate cortex removal. J Neurosci 9(6):2033-50. ↑ Dubner R., zeki s (1971). Propiedades de respuesta y campos receptivos de células en una región anatómicamente definida del surco temporal superior en el mono.. Res del cerebro 35 (2): 528-32. PMID 5002708. ↑ Maunsell J., van essen d (1983). Propiedades funcionales de las neuronas del área visual temporal media del mono macaco. Yo. Selectividad para la dirección del estímulo, velocidad, y orientación.. J Neurofisiol 49 (5): 1127-47. PMID 6864242. ↑ Movshon, J. A., adelson, EH, Gizzi, EM., & Newsome, WT. (1985). El análisis de patrones visuales en movimiento.. En: C. Chagas, R. gattass, & C. Bruto (Eds.), Mecanismos de reconocimiento de patrones (páginas. 117-151), Roma: Prensa del Vaticano. ↑ Britten & Van Wezel 1998 ↑ Wilson, HORA., Ferrera, vicepresidente, & Yo, C. (1992). Un modelo motivado psicofísicamente para la percepción del movimiento bidimensional. Vis Neurosci, 9 (1), 79-97. ↑ Tinsley, cj, Webb, BS, barraclough, NORDESTE., Vicente, cj, Parker, Un., & Derrington, SOY. (2003). La naturaleza de las respuestas neurales de V1 a los patrones de movimiento 2D depende de la estructura del campo receptivo en el mono tití. J Neurofisiol, 90 (2), 930-937. ↑ Pack & Born, 2003 ↑ AlbrightT (1984). Selectividad de dirección y orientación de las neuronas en el área visual MT del macaco.. J Neurofisiol 52 (6): 1106-30. PMID 6520628. ↑ De Angelis G., Nuevo W (1999). Organización de neuronas selectivas de disparidad en el área MT de macacos.. J Neurosci 19 (4): 1398-415. PMID 9952417. External links The Primary Visual Cortex by Matthew Schmolesky at University of Utah Architecture of the Visual Cortex, by David Hubel at Harvard University BrainInfo at the University of Washington ancil-415 - striate area 17 BrainInfo at the University of Washington ancil-699 - Área de Brodmann 17 in guenon BrainMaps at UCDavis visual%20cortex Computational Maps in the Visual Cortex at Simulator for computational modeling of visual cortex maps at Telencephalon (telencéfalo, corteza cerebral, hemisferios cerebrales) - editar surcos/fisuras primarias: longitudinal medial, lateral, central, parietoöccipital, calcarina, lóbulo frontal cingulado: giro precentral (corteza motora primaria, 4), surco precentral, giro frontal superior (6, 8), giro frontal medio (46), giro frontal inferior (área de Broca, 44-pars opercularis, 45-pars triangularis), corteza prefrontal (corteza orbitofrontal, 9, 10, 11, 12, 47) lóbulo parietal: surco postcentral, giro postcentral (1, 2, 3, 43), lóbulo parietal superior (5), lóbulo parietal inferior (39-giro angular, 40), precúneo (7), Lóbulo occipital del surco intraparietal: corteza visual primaria (17), cuneus, giro lingual, 18, 19 (18 y 19 abarcar todo el lóbulo) lóbulo temporal: giro temporal transversal (41-42-corteza auditiva primaria), giro temporal superior (38, 22-el área de Wernicke), giro temporal medio (21), giro temporal inferior (20), giro fusiforme (36, 37) lóbulo límbico/giro fornicado: corteza cingulada/giro cingulado, cingulado anterior (24, 32, 33), cingulado posterior (23, 31), istmo (26, 29, 30), giro parahipocampal (corteza piriforme, 25, 27, 35), corteza entorrinal (28, 34) corteza subcortical/insular: rhinencephalon, bulbo olfativo, cuerpo calloso, ventrículos laterales, septum pellucidum, epéndimo, cápsula interna, corona radiata, Formación del hipocampo de la cápsula externa.: giro dentado, hipocampo, subículo ganglios basales: Estriado (núcleo caudado, Putamen), núcleo lentiforme (Putamen, globus pallidus), claustrum, cápsula extrema, amígdala, núcleo accumbens Algunas categorizaciones son aproximaciones, y algunas áreas de Brodmann abarcan giroscopios. Sistema sensorial - Sistema visual - editar ojo | Nervio óptico | Quiasma óptico | Tracto óptico | Núcleo geniculado lateral | radiación óptica | Corteza visual Esta página utiliza contenido con licencia Creative Commons de Wikipedia (ver autores).

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