Apperceptive agnosia
Each patient that suffers from apperceptive agnosia does not have brain damage in exactly the same area. However, brain damage in proximity to the occipital lobe is largely correlated with the patterns of deficit seen in apperceptive agnosics. For example, patient JB suffered extensive damage to the parietal-occipital areas to the left cerebral hemisphere leading to his deficit in the ability to name distinguish between structurally similar object.
Visual agnosia
Although visual agnosia can be general, there exist many variants that impair recognition of specific types. These variants of visual agnosia include prosopagnosia (inability to recognize faces), pure word blindness (inability to recognize words, often called "agnosic alexia" or "pure alexia"), agnosias for colors (inability to differentiate colors), agnosias for the environment (inability to recognize landmarks or difficult with spatial layout of an environment, i.e. topographagnosia) and simultanagosia (inability to sort out multiple objects in a visual scene).