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.
Auditory agnosia
Auditory agnosia (with the exception of non-verbal auditory agnosia and amusia) is strongly dependent on damage to both hemispheres. The order of hemispheric damage is irrelevant to manifestation of symptoms, and years could take between the damage of the first hemisphere and the second hemisphere (after which the symptoms suddenly emerge). A study that compared lesion locations, reported that in all cases with bilateral hemispheric damage, at least in one side the lesion included Heschl’s gyrus or its underlying white matter. A rare insight into the etiology of this disorder was reported in a study of an auditory agnosia patient with damage to the brainstem, instead of cortex. fMRI scanning of the patient revealed weak activation of the anterior heschl's gyrus (area R) and anterior superior temporal gyrus. These brain areas are part of the auditory 'what' pathway, and are known from both human and monkey research to participate in the recognition of sounds.