Cognitive map in patients with mild Alzheimer's disease: A computer-generated arena study

Objective: In addition to memory impairment, a tendency to get lost is among the initial symptoms in patients with Alzheimer disease (AD). At least two kinds of wayfinding strategies, egocentric and allocentric, have been proposed. It is believed that people may form a cognitive map after repeated movement in a specific environment, and are able to use it as an aid to navigation. In the present study, we investigated the cognitive maps in early AD patients and their application in a computer-generated arena (CGA). Methods: We invited very mild AD (CDR 0.5) patients and normal controls (NCs) to participate in the current study. Hand-drawing tests were used to assess their supposedly previously formed cognitive maps of familiar environments, and CGA was used to measure their new environment learning as well as the application of the old map. Results: Nineteen patients (8 females, mean age 67.6 years old, education 9.7 years, and MMSE 24) and 18 NCs (10 females, mean age 66.4 years old, education 8.8 years, and MMSE 27) completed the study. In the hand-drawing map part, both groups did equally well. In the new environment learning, NCs did better than the AD group on the third of six trials. As for the old environment navigation experiment, the AD group spent more time than the NCs in finding the target, but showed no difference to NC regarding the path traveled in the target quadrant. Conclusion: Early AD patients maintain their ability to use a cognitive map and keep pretty good allocentric representation of their familiar environments as well as NC do, but probably both groups do not routinely use their cognitive map to navigate in everyday life properly. (C) 2008 Elsevier B.V. All rights reserved.