Apperceptive agnosia
Encyclopedia
Apperceptive Agnosia is the visual disorder that renders a person unable to recognize objects. It is also known as visual space agnosia
. Distinction between shapes is difficult, although other aspects of vision
, such as ability to see detail and colour, remain intact. Recognition of, copying and discriminating between visual stimuli, even of different shapes, is problematic. Apperceptive agnosics cannot complete an object matching task.
Because they are unable to recognize even simple shapes, Apperceptive agnosia is considered a problem in the early part of the visual processing system. As contrasted with patients diagnosed Associative agnosia
, who are able to recognize simple shapes and even copy complex shapes (drawing of an anchor, for example) but are unable to recognize what an object is.
In both cases, identification of objects is entirely based on inferences made by the person based on the colour, size, social, or contextual cues.
A variant of apperceptive agnosia is the inability to recognize objects outside of their normal rotation or orientation.
Agnosia
Agnosia is a loss of ability to recognize objects, persons, sounds, shapes, or smells while the specific sense is not defective nor is there any significant memory loss...
. Distinction between shapes is difficult, although other aspects of vision
Visual perception
Visual perception is the ability to interpret information and surroundings from the effects of visible light reaching the eye. The resulting perception is also known as eyesight, sight, or vision...
, such as ability to see detail and colour, remain intact. Recognition of, copying and discriminating between visual stimuli, even of different shapes, is problematic. Apperceptive agnosics cannot complete an object matching task.
Because they are unable to recognize even simple shapes, Apperceptive agnosia is considered a problem in the early part of the visual processing system. As contrasted with patients diagnosed Associative agnosia
Associative agnosia
People with associative agnosia fail in assigning meaning to an object, animal or building that they can see clearly. Most cases have injury to the occipital and temporal lobes and the critical site of injury appears to be in the left occipital-temporal region, often with involvement of the...
, who are able to recognize simple shapes and even copy complex shapes (drawing of an anchor, for example) but are unable to recognize what an object is.
In both cases, identification of objects is entirely based on inferences made by the person based on the colour, size, social, or contextual cues.
A variant of apperceptive agnosia is the inability to recognize objects outside of their normal rotation or orientation.
Further reading
- Fundamentals of Sensation and Perception, Michael Levine. Oxford University Press (3rd Edition). London, 2000.
- Visual Perception, Tom CornsweetTom N. CornsweetTom N. Cornsweet is an American experimental psychologist, author, inventor, and entrepreneur known best for his pioneering work in visual perception and in the development of ophthalmic instrumentation....
. Harcourt Publishing, London, 1970.