[The relationship between visual agnosia and visual pathway for perception].

We report a patient with a unique visual agnosia, who was thought to have lost visual functions except for the primary visual function. The patient was a 71-year-old woman with progressive memory loss and cerebro-cortical atrophy in MRI; her clinical diagnosis was senile dementia of Alzheimer's type. A battery of tests to detect higher visual dysfunctions was performed. First of all, we presented small dots and lines in front of the patient; the patient was able to recognize them. When a triangle, a tetragon, a cube, pieces of paper of different colors and lines of different length were presented, she was unable to recognize those objects. When pictures of her family members or filled circles of different size including small dots and lines were presented, the patient could only detect those small dots and any of lines; she could not recognize the members of her family. The cerebral blood flow was severely reduced in the occipital lobe except for the striate cortex. These data suggested that the visual function of striate cortex was preserved in this patient; the disturbance of higher visual functions was thought to be caused by the dysfunction of extra striate cortex.