Navigation in Alzheimer's Disease
Navigational Test Environment
Our findings in monkey cortical neurophysiology led us to consider the potential role of disordered optic flow analysis in human visuospatial disorientation. The visuospatial disorientation of Alzheimer's disease (AD) has several relevant features: patients get lost despite their recognizing landmarks, describing the route, recognizing familiar landmarks, and showing relative preservation of other capacities.
Using real-world and virtual navigation tasks we have shown that navigational impairment in aging and AD is not related to memory deficits but instead reflects an inability to link recognized scenes with information regarding their relative location that was obtained when moving through the environment. AD patients show elevated perceptual thresholds for outward radial optic flow. Some older normals and almost all AD >patients show elevated thresholds for in/out radial optic flow This suggests that visuospatial impairment may develop as an independent sign of neurodegenerative disease, possibly preceding conditions that satisfy diagnostic criteria for AD.
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