Agnosias are disorders of recognition, specific to one sensory channel, that affect either the perceptual analysis of the stimulus or the recognition of its meaning. In the visual modality, objects, faces, and colors can be separately disrupted. Apperceptive object agnosia refers to failure to achieve a structured description of the shape of the object. Associative agnosia refers to inability to attribute a meaning to a correctly perceived stimulus. It must be differentiated from optic aphasia, in which the object is recognized but cannot be named in the visual modality. Associative agnosia and optic aphasia are associated with left occipitotemporal damage, and they differ more quantitatively than qualitatively. The inability to recognize familiar faces (prosopagnosia) can appear in isolation and be, in some cases, associated with a lesion confined to the occipitotemporal region of the right hemisphere. These findings are supportive of the idea that faces have a separate representation in the brain.