[Visual agnosia induced by cerebrovascular disease].

Visual objects can be classified into some categories such as faces, landscapes, objects and letters. Visual agnosia specific to one of these categories can occur. This type of visual agnosia occurs at the occipitotemporal lobe lesion where the visual cognitive center exists, and is often induced by vascular disease of the posterior cerebral artery. In this study we categorized the symptoms of visual agnosia and presented the natures of these symptoms of patients, and then investigated the lesions responsible for the symptoms. In addition, we clarified the current most important issue for each symptom. Based on our results, we discussed the visual cognitive functions of the occipitotemporal lobe. The results indicate that visual cognitive dysfunction with respect to faces, landscapes, objects and letters corresponds to prosopagnosia, agnosia for streets, associative object agnosia and pure alexia, respectively. Investigation of the relationship between the symptoms of the above conditions and the responsible regions shows that the right medial-posterior region, right medial-anterior region, both lateral regions (left side is superior) and the left medial region are important in the visual cognition of faces, landscapes, objects and letters, respectively. Thus, it is speculated that the visual cognitive functions occur independently at different regions of the occipitotemporal lobe for each visual category.