Individuals with apperceptive visual agnosia cannot form a whole percept of visual information. Associative visual agnosia, impaired object identification. Individuals with associative agnosia cannot give a meaning to a formed percept. The percept is created, but it would have no meaning for individuals who have an associative agnosia. Subtypes of associative visual agnosia
Achromatopsia, an inability to distinguish different colors. Prosopagnosia, an inability to recognize human faces. Individuals with prosopagnosia know that they are looking at faces, but cannot recognize people by the sight of their face, even people whom they know well. Simultagnosia, an inability to recognize multiple objects in a scene, including distinct objects within a spatial layout and distinguishing between "local" objects and "global" objects, such as being able to see a tree but not the forest or vice versa. Topographagnosia, an inability to process the spatial layout of an environment, including landmark agnosia, difficulty recognizing buildings and places; difficulty building mental maps of a location or scene; and/or an inability to discern the orientation between objects in space. Pure alexia, an inability to read. Orientation agnosia: an inability to judge or determine orientation of objects. Pantomime agnosia: an inability to understand pantomimes (gestures). It appears that the inferior cortical visual cortex is critical in recognizing pantomimes. Patient CK
Background
Patient C.K. was born in 1961 in England and emigrated to Canada in 1980. In January 1988, C.K. sustained a head injury from a motor vehicle accident while out for a jog. Following the accident, C.K.
This was the first evidence for a double dissociation between face and object processing suggesting a face-specific processing system. In popular culture
A famous report on this condition is the title essay of Oliver Sacks book, The Man Who Mistook His Wife for a Hat. The murder suspect in the Picket Fences episode "Strangers" supposedly had agnosia. The patient in the House episode "Adverse Events" had agnosia. In the graphic novel Preacher, the character Lorie has an extreme version of agnosia resulting from being born with a single eye. For example, she perceives Arseface, a man with severe facial deformities, as resembling a young James Dean. Val Kilmers character has visual agnosia in the film At First Sight. In "Folie à Deux", a fifth-season episode of The X-Files, Mulder succumbs to the same belief as telemarketer Gary Lambert, that his boss Greg Pincus is a monster who disguises his true appearance by means of hypnosis. Scully, although believing this notion preposterous, suggests that what Mulder describes is analogous to an induced visual agnosia. The short story "Liking What You See: A Documentary" by Ted Chiang examines the cultural effects of a noninvasive medical procedure that induces a visual agnosia toward physical beauty. In the manga and anime Odd Taxi, the main character Odokawa has agnosia, which causes him to see himself and everyone around him as an animal. See also
References
Further reading
Cant JD, Goodale MA (March 2007). "Attention to form or surface properties modulates different regions of human occipitotemporal cortex". Cereb. Cortex. 17 (3): 713–31. doi:10.1093/cercor/bhk022. PMID 16648452.