Agnosia: Visual

Visual agnosia refers to a class of disorders in the domain of visual recognition, in which the affected person cannot arrive at the meaning of some or all categories of visual stimuli. In such cases, knowledge of the shape, form, or other stored knowledge of the physical attributes of an object cannot be accessed, with the result that the stimulus is not successfully identified. The failure to recognize the object occurs under a whole range of conditions and independent of whether the stimulus is presented as a real three-dimensional object, as a black-and-white line drawing, or as a photograph. Dramatically, these perceptual failures occur despite the individual exhibiting normal or near-normal elementary visual functions such as acuity, brightness discrimination, and color vision, along with normal ...