Allothetic orientation and sequential ordering of places is impaired in early stages of Alzheimer's disease: corresponding results in real space tests and computer tests.

Spatial disorientation and learning problems belong to the integral symptoms of Alzheimer's disease (AD). A circular arena for human subjects (2.9 m diameter, 3 m high) was equipped with a computerized tracking system, similar to that used in animals. We studied navigation in 11 subjects diagnosed with early stages of Alzheimer's disease (AD), 27 subjects with subjective problems with memory or concentration, and 10 controls. The task was to locate one or several unmarked goals using the arena geometry, starting position and/or cues on the arena wall. Navigation in a real version and a computer map view version of the tests yielded similar results. The AD group was severely impaired relative to controls in navigation to one hidden goal in eight rotated positions. The impairment was largest when only the cues on the wall could be used for orientation. Also, the AD group recalled worse than controls the order of six sequentially presented locations, though they recalled similarly to controls the positions of the locations. The group with subjective problems was not impaired in any of the tests. Our results document the spatial navigation and non-verbal episodic memory impairment in the AD. Similar results in real and map view computer tests support the use of computer tests in diagnosis of cognitive disturbances.

A battery of tests for quantitative examination of idiothetic and allothetic place navigation modes in humans.

Research into the neural mechanisms of place navigation in laboratory animals has led to the definition of allothetic and idiothetic navigation modes that can be examined by quantitative analysis of the generated tracks. In an attempt to use this approach in the study of human navigation behavior, 10 young subjects were examined in an enclosed arena (2.9 m in diameter, 3 m high) equipped with a computerized tracking system. Idiothetic navigation was studied in blindfolded subjects performing the following tasks-Simple Homing, Complex Homing and Idiothesis Supported by Floor-Related Signals. Allothetic navigation was examined in sighted subjects instructed to find in an empty arena the acoustically signaled unmarked goal region and later to retrieve its position using tasks (Natural Navigation, Cue-Controlled Navigation, Snapshot Memory, Map Reading) that evaluated different aspects of allothesis. The results indicate that allothetic navigation is more accurate than idiothetic, that the poor accuracy of idiothesis is due to angular rather than to distance errors, and that navigation performance is best when both allothetic and idiothetic modes contribute to the solution of the task. The proposed test battery may contribute to better understanding of the navigation disturbances accompanying various neurological disorders and to objective evaluation of the results of drug therapy and of rehabilitation procedures.