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Lost without it

Lost without it

作者:仉旨旧  时间:2019-03-08 08:16:23  人气:

By Lila Guterman in Boston WHEN Alzheimer’s patients lose their bearings, it may be their vision that is at fault. Neurologists in New York say patients can’t interpret the visual cues we use to work out which direction we are moving in. Confusion in people with Alzheimer’s disease is thought to be linked to loss of memory, so when patients get lost, doctors assume they have forgotten where they are going. But Charles Duffy of the University of Rochester, who has studied how monkeys process visual patterns to tell them which way they are moving, wondered if faulty vision processing also contributed to the problem. To test this, he and his colleagues asked 11 people with Alzheimer’s and 18 healthy subjects to watch patterns on a giant computer screen. The screen showed dots streaming outwards from a spot, giving the impression that the observer is moving forward. The team then tested the volunteers’ ability to detect these patterns in the presence of other dots moving randomly. If 15 per cent of the dots moved radially, the young and elderly healthy people could pick out the origin of the radial pattern. But the Alzheimer’s patients needed more than twice as many dots to be moving radially to identify this (Neurology, vol 52, p 958). “In the noise-filled environment of walking around, they are just not getting the same signal quality,” Duffy concludes. “They can’t see where they are going.” What’s more, six of the Alzheimer’s patients in the study had far more trouble than the other five in interpreting the patterns. The same six people also had more difficulty answering questions about the route they followed through the hospital to get to the lab. Duffy suspects that problems interpreting movement could be an early symptom of Alzheimer’s disease. Physicians might be able to use his radial dot test to diagnose the disease early and begin treatment, he suggests,