SENSORY DEFICITS IN VISUAL AGNOSIA

Visual agnosia.

The visual agnosias are an intriguing class of clinical phenomena that have important implications for current theories of high-level vision. Visual agnosia is defined as impaired object recognition that cannot be attributed to visual loss, language impairment, or a general mental decline. At least in some instances, agnostic patients generate an adequate internal representation of the stimulus...

Preserved visual imagery in visual form agnosia.

We investigated the ability of a patient (D.F.) with profound visual form agnosia to perform a variety of tasks requiring visual imagery. Despite her inability to discriminate between objects and patterns of different shapes, sizes, and orientations, D.F. showed quite normal visual imagery involving these same 'visual' properties when the images were drawn from long-term memory. Thus, she was a...

Evidence for perceptual deficits in associative visual (prosop)agnosia: a single-case study.

Associative visual agnosia is classically defined as normal visual perception stripped of its meaning [Archiv für Psychiatrie und Nervenkrankheiten 21 (1890) 22/English translation: Cognitive Neuropsychol. 5 (1988) 155]: these patients cannot access to their stored visual memories to categorize the objects nonetheless perceived correctly. However, according to an influential theory of visual ag...

2D but not 3D: pictorial-depth deficits in a case of visual agnosia.

Patients with visual agnosia exhibit acquired impairments in visual object recognition, that may or may not involve deficits in low-level perceptual abilities. Here we report a case (patient DM) who after head injury presented with object-recognition deficits. He still appears able to extract 2D information from the visual world in a relatively intact manner; but his ability to extract pictoria...

Visual sensory processing deficits in first-episode patients with Schizophrenia.