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A 54 year old woman presented with visual disturbance followed by geographical disorientation for 3 years. Neurological and neuropsychological examinations were remarkable for severe simultanagnosia accompanied by optic ataxia, oculomotor apraxia, and prosopagnosia without colour agnosia. Also, she had contructional and dressing apraxia, impaired naming, ideomotor apraxia, acalculia, and right-left disorientation with intact conversational speech and semantic word fluency. Although verbal and visual memories were compromised on formal memory tests, episodic memory in daily living was preserved. Brain 18F-fluoro-2-deoxy-D-glucose PET showed marked hypometabolism involving bilateral temporoparietooccipital areas (fig1 A), which, together with clinical features, was consistent with posterior cortical atrophy.
Immediately after a calibration, each of two modified Navon figures (fig 1 B) was presented on the computer screen and the patient and a 53 year old female control were asked to find “star” on the number “4” composed of symbols (left of fig 1 B) and to find number “4” on a Korean letter (meaning “ball”) composed of numbers (right of fig 1 B). With head and chin fixation, the subjects' left eye was monitored for 10 seconds after presentation of stimuli, using video-oculography (SMI, Germany), which allowed 60 measurements a second with resolution of 0.1°. The control scanned the whole stimuli (fig1 C), whereas the patient scanned only focal areas of the global figures (fig1 D). Simultanagnosia may result from either deficient scanning ability or failure to organise pieces of visual information at the mental representational level despite intact scanning ability. Our patient's results may support the deficient scanning ability theory.
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