The phenomenon of ‘blindsight’ is much discussed, but little understood. What does ‘blindness’ really mean in the context of blindsight?
Blindsight represents a phenomena whereby the person cannot see the object that lies within his blind field but can reach for it in an accurate manner (Carlson, 2001a). In simple words it is the inability to consciously see the visual stimulus or a light source but can sense it accurately. Datta (2006) observed that the damage which takes place in blindsight rendering the person blind as to visual stimulus is the contralateral element of the visual field. This is the part which is involved in the vision processing and is a primary part of visual striate cortext in human beings. (Parkin, 1996)
Parkin (1996) referred to a patient in his work that the patient suffered a brain damage which corresponded to the right virtual cortex. This rendered him unable to see the things which were present before the lower left quadrant of each of his eyes. Parkin (1996) observed that the patient couldn’t consciously see the things but could locate them i.e. he could process them unconsciously. Datta (2006) named it as ‘unconscious processing’. Farah, O’Reilly & Vecera (1993) observed that this unconscious processing takes place in the extrastriate cortex which involves dorsal lateral geniculate nucleus and superior colliculus.
Datta (2006) observed that other mammals too have suffered from blindsight. Datta (2006) referred to a monkey, named Helen, whose primary visual cortex got destroyed completely and she couldn’t see anything consciously at all. But the monkey was still able to locate things that were placed in front of her. Carlson (2001) said that this shows that the behaviour can be controlled by visual information which can also control the visual movement without any conscious perception to be made or visual sensation to be developed....
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