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The visual cortex of the brain is the part of the cerebral cortex responsible for processing visual information. This article addresses the ventral/dorsal model of the visual cortex. Another model for the perceptual/conceptual neuropsychological model of the visual cortex was studied by Raftopolous.〔Anastasios Raftopolous, ''Cognition and Perception'', Oxford University Press, 2009.〕 In Russian neuropsychology, yet another model was discussed by Alexander Luria for the anterior/posterior approach to understanding the visual cortex.〔Alexander Luria (1961). ''Higher Cortical Functions in Man'', Basic Books.〕 The visual cortex is located in the occipital lobe (one of the four major lobes of the cerebral cortex) which is in turn located at the back of the head or skull. The visual cortex is made up of Brodmann area 17 (the primary visual cortex), and Brodmann areas 18 and 19, the extrastriate cortical areas. The primary (parts of the cortex that receive sensory inputs from the thalamus) visual cortex is also known as V1, Visual area one, and the striate cortex. The extrastriate areas consist of visual areas two (V2), three (V3), four (V4), and five (V5). Both hemispheres of a brain contain a visual cortex; the left hemisphere visual cortex receives signals from the right visual field, and the right visual cortex from the left visual field. ==Introduction== This article addresses the ventral/dorsal model of the visual cortex. Another model for the perceptual/conceptual neuropsychological model of the visual cortex was studied by Raftopolous.〔 In Russian neurospychology, yet another model was discussed by Alexander Luria for the anterior/posterior approach to understanding the visual cortex.〔 The primary visual cortex, V1, is the koniocortex (sensory type) located in and around the calcarine fissure in the occipital lobe. Each hemisphere's V1 receives information directly from its ipsilateral lateral geniculate nucleus that receives signs from the contralateral visual field. Each V1 transmits information to two primary pathways, called the ventral stream and the dorsal stream. * The ventral stream begins with V1, goes through visual area V2, then through visual area V4, and to the inferior temporal cortex (IP 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 dorsal stream begins with V1, goes through Visual area V2, then to the dorsomedial area (DM/ V6) and Visual area MT (middle temporal/ V5) and to the posterior parietal cortex. The dorsal stream, sometimes called the "Where Pathway" or "How 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. The what vs. where account of the ventral/dorsal pathways was first described by Ungerleider and Mishkin. More recently, Goodale and Milner extended these ideas and suggested that the ventral stream is critical for visual perception whereas the dorsal stream mediates the visual control of skilled actions. Although these ideas are contentious among some vision scientists and psychologists, the proposed division of labor between ''vision-for-perception'' and ''vision-for-action'' is supported by a broad range of findings from neuropsychology, neurophysiology, and neuroimaging. Some of the most controversial evidence comes from studies of visuomotor behaviour in normal observers. For example, it has been shown that visual illusions such as the Ebbinghaus illusion distort judgements of a perceptual nature, but when the subject responds with an action, such as grasping, no distortion occurs. Other work such as the one from Scharnowski and Gegenfurtner suggests that both the action and perception systems are equally fooled by such illusions. More recent studies, however, provide strong support for the idea that skilled actions such as grasping are not affected by pictorial illusions and suggest that the action/perception dissociation is a useful way to characterize the functional division of labor between the dorsal and ventral visual pathways in the cerebral cortex. Neurons in the visual cortex fire action potentials when visual stimuli appear within their receptive field. By definition, the receptive field is the region within the entire visual field that elicits an action potential. But, for any given neuron, it may respond best to a subset of stimuli within its receptive field. This property is called ''neuronal tuning''. In the earlier visual areas, neurons have simpler tuning. For example, a neuron in V1 may fire to any vertical stimulus in its receptive field. In the higher visual areas, neurons have complex tuning. For example, in the inferior temporal cortex (IT), a neuron may fire only 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Visual cortex」の詳細全文を読む スポンサード リンク
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