Impairment in allocentric orientation and memory for the order of locations in different stages of Alzheimer's disease

K. Vlcek¹, E. Kalová², J. Laczo³, E. Jarolímová⁴, J. Hort³ and J. Bureš¹

¹Department of Neurophysiology of Memory, Academy of Sciences, Czech Republic
²Neurology, Na Homolce Hospital, Prague, Czech Republic
³Neurology, Motol Hospital , Prague, Czech Republic
⁴Gerontology centrum, Prague, Czech Republic

Spatial disorientation is frequently observed in Alzheimer's disease (AD). We developed two tests to specify impairment in allocentric and idiocentric navigation and in spatial memory for several locations. Both real space version in a 2.8 m diameter circular arena and map-view computer version was used. Comparison was made among groups diagnosed with early and middle stages of AD, a group with Mild Cognitive Impairment (MCI) and a control group. In the first test (hidden goal task, HGT), the subject should find a hidden goal inside of the arena. Depending on the specific subtest, the start position and/or cues on the arena wall could be used for idiothetic and/or allothetic orientation, respectively. In the second test (memory test), the subject was shown 2, 4 or 6 locations inside of the arena and then was asked to recall their position in the order they were presented. The errors in the remembered order and in locations of the points were evaluated separately. The people in the middle stages of AD either did not understood the instructions or were severely impaired in all tests. The subjects in the early stages of AD navigated worse than controls in all subtests of the Hidden Goal Task and were impaired in remembering the order of four and six points in the Spatial memory taks. The group diagnosed with MCI was impaired only in remembering the order and locations of six points in computer version of Spatial memory task. Our results suggest general spatial navigation impairment in AD and spatial working memory impairment in the early stages of AD. We were able to distinguish the MCI group from controls in the Spatial memory task. Supported by GACR grant 309/05/0693.

Paper presented at Measuring Behavior 2005 , 5^th International Conference on Methods and Techniques in Behavioral Research, 30 August - 2 September 2005, Wageningen, The Netherlands.

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