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.
Associative visual agnosia
Pure alexia ("alexia without dysgraphia" or "pure word blindness") is a category-specific agnosia, characterized by a distinct impairment in reading words, despite intact comprehension for verbally presented words, demonstrating retained semantic knowledge of words. Perceptual abilities are also intact, as assessed by word-copying tasks.