DB is a 67-year-old man whose view of the world is dark from the center of his gaze leftward. He has been blind to this left part of his visual scene since age 33, when he had surgery to remove an abnormal tangle of blood vessels at the back of his brain. Unfortunately, while taking out the tangle, surgeons destroyed an important center of visual processing called the primary visual cortex, or area V1, which relays information from the eyes to higher-level brain areas dedicated to sight.

DB lost just the right half of V1. Because the right part of the brain processes visual information from the left visual field (and vice versa), his doctors were not surprised that DB became blind to the left portion of his view. But they were astounded that although DB denied seeing anything to the left of center, he was nonetheless able to accurately “guess” many properties of targets, such as shape and specific location, presented in this perceptually dark field.

This article was originally published with the title Subconscious Sight.

3 Comments

1. 1. Dr A Breck McKay 07:11 AM 4/13/08

   Why does everyone forget the sub-200 millisecond responses, (auditory, visual and olfactory), that occur via the direct connections to the vestibulo-autonomic mechanism in the mid brain? These are our immediate response to external threats and occur long before any V1 area activations. It is via these fast activations that all animals are able to immediately respond with Flight/fight or Fear/freeze to threats before they are recognised by the higher centre areas. This is Prof Ivan Pavlov's (1910 Lecture) Orienting or Focusing Reflex.

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2. 2. BesenSA 05:25 PM 10/14/09

   Quite right Dr McKay; "everyone" being mostly philosophers of mind, and scientists whose concept of the human world follows the ancient idea of a non-physical 'mind' which can do any damn thing required to fulfill the the ancient ideas.
   There is no concept of how a complex physical system such as the neuro-chemical brain can develop a 'conscious' self. The bulk of the cognitive saystem operates in a non-concscious mode, some 500ms ahead of the conscious mode. See Dr Benjamin Libet's work which makes voluntary actions the work of the brain without the mysterious concscious system. Any explantation of the human cognate system, including emotional reactions which depends on conscious reports is simply confabulation. Until there is a better model of the operation of the neuro-chemical brain system for fixing and associating memory, and creating 'reality', the explanations given by Mind scientists will be faulty.
   
   irv Besen

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3. 3. swissms 04:26 AM 4/1/10

   I read Weiskrantz's book and there is no mention of any thought given to synesthesia. We are missing the opportunity to learn how our sensory apparatus may crossover to provide information, or how we actually may perceive beyond the apparatus.

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