[Visual object agnosia: current conceptions].
Visual agnosia for objects is a difficulty in recognizing objects presented visually. This difficulty can not be explained by a mental deterioration, a disorder of attention or a lack of familiarity with the object. Two criteria are essential but disputed: the absence of visual sensory difficulty necessary for adequate perception; possible recognition of the object by another sensory modality. An object is characterized by a triple representation: formal, semantic, lexical. The clinical, cognitive, pathophysiological analysis lead to distinguish 3 types of visual agnosia. 1) Aperceptive visual agnosia: patients see badly with morphological errors; the disorder concerns visual informations processing that is a necessary condition for identifying the formal representation of the object; the lesions are bilateral and involve the occipito-temporal cortex. 2) Associative visual agnosia: patients can copy, are not aphasic, but give erroneous verbal responses; the disorder concerns the links between formal representations and semantic, lexical representations; the lesions are unilateral and involve the left gyrus angularis connections. 3) Asemantic visual agnosia: patients have lost the meanings of objects and words; the disorder concerns semantic representations; the lesions are bilateral and involve the temporo-limbic cortex.
Cambier
J
J
Clinique Neurologique, Hôpital Beaujon, Paris.
Signoret
J L
JL
Bolgert
F
F
D000377:Agnosia / Q000503:physiopathology*; D001925:Brain Damage, Chronic / Q000503:physiopathology; D005556:Form Perception / Q000502:physiology; D006801:Humans; D014796:Visual Perception / Q000502:physiology*
L'agnosie visuelle pour les objets: conceptions actuelles.