22 Mar 1999

It has long been assumed that the reason Alzheimer patients tend to get lost is because of memory failure and confusion. But a new study appearing in tomorow’s issue of Neurology suggests that impaired processing of visual information may contribute to the problem. In the study, six healthy young people, 12 healthy older people, and 11 Alzheimer's patients were tested on their ability to interpret visual patterns. In one test, the subjects viewed a computer screen displaying a radiating pattern simulating the visual changes that occur when one moves through space. The subjects were asked to decide whether it looked like they were moving to the left or to the right. People with Alzheimer’s had twice as much difficulty interpreting the scene as did healthy subjects. "People with Alzheimer's get lost not because they don't remember where they've been, but because they can't see where they're going," says Charles Duffy, an author of the study. Tests such as those used in the study could be useful in early diagnosis of AD, because visual disorientation is often one of first symptoms seen in patients. The tests could also be used to identify those at particular risk for getting lost, Duffy said, such as those who shouldn't be driving due to their visual disorientation.—June Kinoshita