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Additional recommended knowledge
Visual processing in the brain goes through a series of stages. Destruction of the first visual cortical area, primary visual cortex (or V1 or striate cortex) leads to blindness in the part of the visual field that corresponds to the damaged cortical representation. The area of blindness - known as a scotoma - is in the visual field opposite the damaged hemisphere and can vary from a small area up to the entire hemifield.
Although individuals with damage to V1 are not consciously aware of stimuli presented in their blind field, Lawrence Weiskrantz and colleagues showed in the early 1970s that if forced to guess about whether a stimulus is present in their blind field, some observers do better than chance. This ability to detect stimuli that the observer is not conscious of can extend to discrimination of the type of stimulus (for example, whether an 'X' or 'O' has been presented in the blind field). This general phenomenon has been dubbed "blindsight".
It is unsurprising from a neurological viewpoint that damage to V1 leads to reports of blindness. Visual processing occurs in the brain in a hierarchical series of stages (with much crosstalk and feedback between areas). As V1 is the first cortical area in this hierarchy, any damage to V1 severely limits visual information passing from the retina, via the LGN and then V1, to higher cortical areas. However, the route from the retina through V1 is not the only visual pathway into the cortex, though it is by far the largest; it is commonly thought that the residual performance of people exhibiting blindsight is due to preserved pathways into the extrastriate cortex that bypass V1. What is surprising is that activity in these extrastriate areas is apparently insufficient to support visual awareness in the absence of V1.
Notable medical fiction authors including Robin Cook write extensively on this condition . Other medical fiction authors include Tess Gerritsen; Brett Chatz; Patricia Cornwell and Michael Palmer.[clarify][specify]
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Blindsight". A list of authors is available in Wikipedia.|