Visual apperceptive agnosia is a visual impairment that results in patients inability to name objects. While agnosics suffer from severe deficits, patients visual acuity and other visual abilities such as perceiving parts and colours remain intact. Deficits seem to occur because of damage to early-level perceptual processing. While patients are able to effectively allocate attention to locate the object and perceive the parts, they are unable to group together the parts they see and name the object accurately. This is demonstrated by the fact that patients are more effective at naming two attributes from a single object than they are able to name one attribute on each of the two superimposed objects. In addition they are still able to describe objects in detail and recognize objects by touch.
Apperceptive visual agnosia seems to occur because patients essentially see the world through random visual noise that occurs from random widespread scotomas. In addition, difficulties seem to arise from an inability to perceptually group together perceptual elements in the visual field. Researchers have been able to mimic Apperceptive visual agnosia in visually intact participants. Results have shown that object agnosia can be mimicked by introducing a filter with random visual noise. When crucial aspects are removed from objects to mimic the perceptual grouping deficit of agnosics,participants also showed object recognition deficits. This indicates that Apperceptive agnosia results from both a peppery mask and an inability to group perceptual objects.
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