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
While most cases of visual agnosia are seen in older adults who have experienced extensive brain damage, there are also cases of young children with less brain damage during developmental years acquiring the symptoms. Commonly, visual agnosia presents as an inability to recognize an object in the absence of other explanations, such as blindness or partial blindness, anomia, memory loss, etc.. Other common manifestations of visual agnosia that are generally tested for include difficulty identifying objects that look similar in shape, difficulty with identifying line drawings of objects, and recognizing objects that are shown from less common views, such as a horse from a top-down view.