However, this difficulty is not considered agnosia. Presumably their memories and associations to the object are intact. Their difficulty is confined to the language aspects of expressing knowledge about the object. Their ability to name the object does not improve when information about the object is presented in another modality. In contrast, patients with agnosia will often improve when information is presented in other modalities.
Visual agnosia is associated with lesions of the left occipital and temporal lobes.
Many patients have a severe visual field defect on the right side because of the injuryto the left occipital lobe. It is common for patients to have visual agnosia but intact recognition in the tactile and auditory modalities. Patients with color anomia perform normally on tasks that require discrimination of colors but cannot name colors or point to colors named by the examiner. There is a distinction between color perception versus color recognition. Patients with prosopagnosia can identify faces as such but they do not recognize whose face is present before them.