Visual agnosia and cognitive defects in a case of Alzheimer's disease.

A patient with Alzheimer's disease, who is still alive, was investigated using a battery of tests, including design-copying and identification, the Gottschaldt hidden figures, a reading test, picture identification, and identification of tachistoscopically presented figures. The main observations were (i) an inability to handle more than one "element" of visual input simultaneously, (ii) an inability to attain and sustain a correct test performance. This last feature was assumed to be related to a difficulty in establishing and sustaining a set or attitude about how to solve the task. The hypothesis was put forward that both behavioral characteristics were related to a deficient task-related arousal-increasing mechanism.