Visual agnosia
From Psy3241
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Visual Agnosia
Visual Agnosia is the inability to make sense of what is being viewed. Markedly different from the inability to see completely, or blindness, individuals suffering from Visual Agnosia are able to see objects and describe them in great detail but are unable to process these observations as a whole and name what they are looking at.
Object Identification
Visual Agnostic patients generally can hold an object while looking at is and name what it is. The combination of tactile information as well as visual information enables them to piece together the complex process of identification. The same holds true for auditory information coupled with visual information.
Causes
Visual Agnosia is generally associated with damage to the posterior occipital or temporal lobes of the brain. Rarely does damage to the retina or optical nerve result in a form of Agnosia. Virgil is an example of an exception to this generalization (Sacks, 1990),
Virgil
Virgil had his cataracts removed late in life and was finally able to see but was unable to make sense of what he was seeing. For Example the moment the bandages came off Virgil's eyes he explained that "there was light, there was movement, there was color, all mixed up, all meaningless, a blur."
Dr. P
The Man Who Mistook his Wife for a Hat is a commonly cited source as an example of Visual Agnosia. Dr. P, the patient, who after believing his testing was finished for the afternoon began to look around for his hat in preparation to leave. His face suggested he had found it, and he reached for the hat which was his wife's head and tried to lift it off. He had mistaken his wife for his hat.
sources
http://ahsmail.uwaterloo.ca/kin356/ventral/visual_agnosia.htm
Sacks, O.. (1990). To See or Not to See.
Sacks, O.. (1998). The Man Who Mistook his Wife for a Hat.
--Jmueller 14:19, 24 April 2008 (EDT)
